Index: stable/9/sys/kern/kern_lock.c =================================================================== --- stable/9/sys/kern/kern_lock.c (revision 226254) +++ stable/9/sys/kern/kern_lock.c (revision 226255) @@ -1,1457 +1,1454 @@ /*- * Copyright (c) 2008 Attilio Rao * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice(s), this list of conditions and the following disclaimer as * the first lines of this file unmodified other than the possible * addition of one or more copyright notices. * 2. Redistributions in binary form must reproduce the above copyright * notice(s), this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH * DAMAGE. */ #include "opt_adaptive_lockmgrs.h" #include "opt_ddb.h" #include "opt_kdtrace.h" #include __FBSDID("$FreeBSD$"); #include #include #include #include #include #include #include #include #ifdef DEBUG_LOCKS #include #endif #include #include #include #ifdef DDB #include #endif CTASSERT(((LK_ADAPTIVE | LK_NOSHARE) & LO_CLASSFLAGS) == (LK_ADAPTIVE | LK_NOSHARE)); CTASSERT(LK_UNLOCKED == (LK_UNLOCKED & ~(LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS))); #define SQ_EXCLUSIVE_QUEUE 0 #define SQ_SHARED_QUEUE 1 +#ifdef ADAPTIVE_LOCKMGRS +#define ALK_RETRIES 10 +#define ALK_LOOPS 10000 +#endif + #ifndef INVARIANTS #define _lockmgr_assert(lk, what, file, line) #define TD_LOCKS_INC(td) #define TD_LOCKS_DEC(td) #else #define TD_LOCKS_INC(td) ((td)->td_locks++) #define TD_LOCKS_DEC(td) ((td)->td_locks--) #endif #define TD_SLOCKS_INC(td) ((td)->td_lk_slocks++) #define TD_SLOCKS_DEC(td) ((td)->td_lk_slocks--) #ifndef DEBUG_LOCKS #define STACK_PRINT(lk) #define STACK_SAVE(lk) #define STACK_ZERO(lk) #else #define STACK_PRINT(lk) stack_print_ddb(&(lk)->lk_stack) #define STACK_SAVE(lk) stack_save(&(lk)->lk_stack) #define STACK_ZERO(lk) stack_zero(&(lk)->lk_stack) #endif #define LOCK_LOG2(lk, string, arg1, arg2) \ if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \ CTR2(KTR_LOCK, (string), (arg1), (arg2)) #define LOCK_LOG3(lk, string, arg1, arg2, arg3) \ if (LOCK_LOG_TEST(&(lk)->lock_object, 0)) \ CTR3(KTR_LOCK, (string), (arg1), (arg2), (arg3)) #define GIANT_DECLARE \ int _i = 0; \ WITNESS_SAVE_DECL(Giant) #define GIANT_RESTORE() do { \ if (_i > 0) { \ while (_i--) \ mtx_lock(&Giant); \ WITNESS_RESTORE(&Giant.lock_object, Giant); \ } \ } while (0) #define GIANT_SAVE() do { \ if (mtx_owned(&Giant)) { \ WITNESS_SAVE(&Giant.lock_object, Giant); \ while (mtx_owned(&Giant)) { \ _i++; \ mtx_unlock(&Giant); \ } \ } \ } while (0) #define LK_CAN_SHARE(x) \ (((x) & LK_SHARE) && (((x) & LK_EXCLUSIVE_WAITERS) == 0 || \ ((x) & LK_EXCLUSIVE_SPINNERS) == 0 || \ curthread->td_lk_slocks || (curthread->td_pflags & TDP_DEADLKTREAT))) #define LK_TRYOP(x) \ ((x) & LK_NOWAIT) #define LK_CAN_WITNESS(x) \ (((x) & LK_NOWITNESS) == 0 && !LK_TRYOP(x)) #define LK_TRYWIT(x) \ (LK_TRYOP(x) ? LOP_TRYLOCK : 0) #define LK_CAN_ADAPT(lk, f) \ (((lk)->lock_object.lo_flags & LK_ADAPTIVE) != 0 && \ ((f) & LK_SLEEPFAIL) == 0) #define lockmgr_disowned(lk) \ (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == LK_KERNPROC) #define lockmgr_xlocked(lk) \ (((lk)->lk_lock & ~(LK_FLAGMASK & ~LK_SHARE)) == (uintptr_t)curthread) static void assert_lockmgr(struct lock_object *lock, int how); #ifdef DDB static void db_show_lockmgr(struct lock_object *lock); #endif static void lock_lockmgr(struct lock_object *lock, int how); #ifdef KDTRACE_HOOKS static int owner_lockmgr(struct lock_object *lock, struct thread **owner); #endif static int unlock_lockmgr(struct lock_object *lock); struct lock_class lock_class_lockmgr = { .lc_name = "lockmgr", .lc_flags = LC_RECURSABLE | LC_SLEEPABLE | LC_SLEEPLOCK | LC_UPGRADABLE, .lc_assert = assert_lockmgr, #ifdef DDB .lc_ddb_show = db_show_lockmgr, #endif .lc_lock = lock_lockmgr, .lc_unlock = unlock_lockmgr, #ifdef KDTRACE_HOOKS .lc_owner = owner_lockmgr, #endif }; -#ifdef ADAPTIVE_LOCKMGRS -static u_int alk_retries = 10; -static u_int alk_loops = 10000; -SYSCTL_NODE(_debug, OID_AUTO, lockmgr, CTLFLAG_RD, NULL, "lockmgr debugging"); -SYSCTL_UINT(_debug_lockmgr, OID_AUTO, retries, CTLFLAG_RW, &alk_retries, 0, ""); -SYSCTL_UINT(_debug_lockmgr, OID_AUTO, loops, CTLFLAG_RW, &alk_loops, 0, ""); -#endif - static __inline struct thread * lockmgr_xholder(struct lock *lk) { uintptr_t x; x = lk->lk_lock; return ((x & LK_SHARE) ? NULL : (struct thread *)LK_HOLDER(x)); } /* * It assumes sleepq_lock held and returns with this one unheld. * It also assumes the generic interlock is sane and previously checked. * If LK_INTERLOCK is specified the interlock is not reacquired after the * sleep. */ static __inline int sleeplk(struct lock *lk, u_int flags, struct lock_object *ilk, const char *wmesg, int pri, int timo, int queue) { GIANT_DECLARE; struct lock_class *class; int catch, error; class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL; catch = pri & PCATCH; pri &= PRIMASK; error = 0; LOCK_LOG3(lk, "%s: %p blocking on the %s sleepqueue", __func__, lk, (queue == SQ_EXCLUSIVE_QUEUE) ? "exclusive" : "shared"); if (flags & LK_INTERLOCK) class->lc_unlock(ilk); if (queue == SQ_EXCLUSIVE_QUEUE && (flags & LK_SLEEPFAIL) != 0) lk->lk_exslpfail++; GIANT_SAVE(); sleepq_add(&lk->lock_object, NULL, wmesg, SLEEPQ_LK | (catch ? SLEEPQ_INTERRUPTIBLE : 0), queue); if ((flags & LK_TIMELOCK) && timo) sleepq_set_timeout(&lk->lock_object, timo); /* * Decisional switch for real sleeping. */ if ((flags & LK_TIMELOCK) && timo && catch) error = sleepq_timedwait_sig(&lk->lock_object, pri); else if ((flags & LK_TIMELOCK) && timo) error = sleepq_timedwait(&lk->lock_object, pri); else if (catch) error = sleepq_wait_sig(&lk->lock_object, pri); else sleepq_wait(&lk->lock_object, pri); GIANT_RESTORE(); if ((flags & LK_SLEEPFAIL) && error == 0) error = ENOLCK; return (error); } static __inline int wakeupshlk(struct lock *lk, const char *file, int line) { uintptr_t v, x; u_int realexslp; int queue, wakeup_swapper; TD_LOCKS_DEC(curthread); TD_SLOCKS_DEC(curthread); WITNESS_UNLOCK(&lk->lock_object, 0, file, line); LOCK_LOG_LOCK("SUNLOCK", &lk->lock_object, 0, 0, file, line); wakeup_swapper = 0; for (;;) { x = lk->lk_lock; /* * If there is more than one shared lock held, just drop one * and return. */ if (LK_SHARERS(x) > 1) { if (atomic_cmpset_rel_ptr(&lk->lk_lock, x, x - LK_ONE_SHARER)) break; continue; } /* * If there are not waiters on the exclusive queue, drop the * lock quickly. */ if ((x & LK_ALL_WAITERS) == 0) { MPASS((x & ~LK_EXCLUSIVE_SPINNERS) == LK_SHARERS_LOCK(1)); if (atomic_cmpset_rel_ptr(&lk->lk_lock, x, LK_UNLOCKED)) break; continue; } /* * We should have a sharer with waiters, so enter the hard * path in order to handle wakeups correctly. */ sleepq_lock(&lk->lock_object); x = lk->lk_lock & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); v = LK_UNLOCKED; /* * If the lock has exclusive waiters, give them preference in * order to avoid deadlock with shared runners up. * If interruptible sleeps left the exclusive queue empty * avoid a starvation for the threads sleeping on the shared * queue by giving them precedence and cleaning up the * exclusive waiters bit anyway. * Please note that lk_exslpfail count may be lying about * the real number of waiters with the LK_SLEEPFAIL flag on * because they may be used in conjuction with interruptible * sleeps so lk_exslpfail might be considered an 'upper limit' * bound, including the edge cases. */ realexslp = sleepq_sleepcnt(&lk->lock_object, SQ_EXCLUSIVE_QUEUE); if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) { if (lk->lk_exslpfail < realexslp) { lk->lk_exslpfail = 0; queue = SQ_EXCLUSIVE_QUEUE; v |= (x & LK_SHARED_WAITERS); } else { lk->lk_exslpfail = 0; LOCK_LOG2(lk, "%s: %p has only LK_SLEEPFAIL sleepers", __func__, lk); LOCK_LOG2(lk, "%s: %p waking up threads on the exclusive queue", __func__, lk); wakeup_swapper = sleepq_broadcast(&lk->lock_object, SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE); queue = SQ_SHARED_QUEUE; } } else { /* * Exclusive waiters sleeping with LK_SLEEPFAIL on * and using interruptible sleeps/timeout may have * left spourious lk_exslpfail counts on, so clean * it up anyway. */ lk->lk_exslpfail = 0; queue = SQ_SHARED_QUEUE; } if (!atomic_cmpset_rel_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x, v)) { sleepq_release(&lk->lock_object); continue; } LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue", __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" : "exclusive"); wakeup_swapper |= sleepq_broadcast(&lk->lock_object, SLEEPQ_LK, 0, queue); sleepq_release(&lk->lock_object); break; } lock_profile_release_lock(&lk->lock_object); return (wakeup_swapper); } static void assert_lockmgr(struct lock_object *lock, int what) { panic("lockmgr locks do not support assertions"); } static void lock_lockmgr(struct lock_object *lock, int how) { panic("lockmgr locks do not support sleep interlocking"); } static int unlock_lockmgr(struct lock_object *lock) { panic("lockmgr locks do not support sleep interlocking"); } #ifdef KDTRACE_HOOKS static int owner_lockmgr(struct lock_object *lock, struct thread **owner) { panic("lockmgr locks do not support owner inquiring"); } #endif void lockinit(struct lock *lk, int pri, const char *wmesg, int timo, int flags) { int iflags; MPASS((flags & ~LK_INIT_MASK) == 0); ASSERT_ATOMIC_LOAD_PTR(lk->lk_lock, ("%s: lockmgr not aligned for %s: %p", __func__, wmesg, &lk->lk_lock)); iflags = LO_SLEEPABLE | LO_UPGRADABLE; if (flags & LK_CANRECURSE) iflags |= LO_RECURSABLE; if ((flags & LK_NODUP) == 0) iflags |= LO_DUPOK; if (flags & LK_NOPROFILE) iflags |= LO_NOPROFILE; if ((flags & LK_NOWITNESS) == 0) iflags |= LO_WITNESS; if (flags & LK_QUIET) iflags |= LO_QUIET; iflags |= flags & (LK_ADAPTIVE | LK_NOSHARE); lk->lk_lock = LK_UNLOCKED; lk->lk_recurse = 0; lk->lk_exslpfail = 0; lk->lk_timo = timo; lk->lk_pri = pri; lock_init(&lk->lock_object, &lock_class_lockmgr, wmesg, NULL, iflags); STACK_ZERO(lk); } /* * XXX: Gross hacks to manipulate external lock flags after * initialization. Used for certain vnode and buf locks. */ void lockallowshare(struct lock *lk) { lockmgr_assert(lk, KA_XLOCKED); lk->lock_object.lo_flags &= ~LK_NOSHARE; } void lockallowrecurse(struct lock *lk) { lockmgr_assert(lk, KA_XLOCKED); lk->lock_object.lo_flags |= LO_RECURSABLE; } void lockdisablerecurse(struct lock *lk) { lockmgr_assert(lk, KA_XLOCKED); lk->lock_object.lo_flags &= ~LO_RECURSABLE; } void lockdestroy(struct lock *lk) { KASSERT(lk->lk_lock == LK_UNLOCKED, ("lockmgr still held")); KASSERT(lk->lk_recurse == 0, ("lockmgr still recursed")); KASSERT(lk->lk_exslpfail == 0, ("lockmgr still exclusive waiters")); lock_destroy(&lk->lock_object); } int __lockmgr_args(struct lock *lk, u_int flags, struct lock_object *ilk, const char *wmesg, int pri, int timo, const char *file, int line) { GIANT_DECLARE; struct lock_class *class; const char *iwmesg; uintptr_t tid, v, x; u_int op, realexslp; int error, ipri, itimo, queue, wakeup_swapper; #ifdef LOCK_PROFILING uint64_t waittime = 0; int contested = 0; #endif #ifdef ADAPTIVE_LOCKMGRS volatile struct thread *owner; u_int i, spintries = 0; #endif error = 0; tid = (uintptr_t)curthread; op = (flags & LK_TYPE_MASK); iwmesg = (wmesg == LK_WMESG_DEFAULT) ? lk->lock_object.lo_name : wmesg; ipri = (pri == LK_PRIO_DEFAULT) ? lk->lk_pri : pri; itimo = (timo == LK_TIMO_DEFAULT) ? lk->lk_timo : timo; MPASS((flags & ~LK_TOTAL_MASK) == 0); KASSERT((op & (op - 1)) == 0, ("%s: Invalid requested operation @ %s:%d", __func__, file, line)); KASSERT((flags & (LK_NOWAIT | LK_SLEEPFAIL)) == 0 || (op != LK_DOWNGRADE && op != LK_RELEASE), ("%s: Invalid flags in regard of the operation desired @ %s:%d", __func__, file, line)); KASSERT((flags & LK_INTERLOCK) == 0 || ilk != NULL, ("%s: LK_INTERLOCK passed without valid interlock @ %s:%d", __func__, file, line)); class = (flags & LK_INTERLOCK) ? LOCK_CLASS(ilk) : NULL; if (panicstr != NULL) { if (flags & LK_INTERLOCK) class->lc_unlock(ilk); return (0); } if (lk->lock_object.lo_flags & LK_NOSHARE) { switch (op) { case LK_SHARED: op = LK_EXCLUSIVE; break; case LK_UPGRADE: case LK_DOWNGRADE: _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, file, line); return (0); } } wakeup_swapper = 0; switch (op) { case LK_SHARED: if (LK_CAN_WITNESS(flags)) WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER, file, line, ilk); for (;;) { x = lk->lk_lock; /* * If no other thread has an exclusive lock, or * no exclusive waiter is present, bump the count of * sharers. Since we have to preserve the state of * waiters, if we fail to acquire the shared lock * loop back and retry. */ if (LK_CAN_SHARE(x)) { if (atomic_cmpset_acq_ptr(&lk->lk_lock, x, x + LK_ONE_SHARER)) break; continue; } lock_profile_obtain_lock_failed(&lk->lock_object, &contested, &waittime); /* * If the lock is already held by curthread in * exclusive way avoid a deadlock. */ if (LK_HOLDER(x) == tid) { LOCK_LOG2(lk, "%s: %p already held in exclusive mode", __func__, lk); error = EDEADLK; break; } /* * If the lock is expected to not sleep just give up * and return. */ if (LK_TRYOP(flags)) { LOCK_LOG2(lk, "%s: %p fails the try operation", __func__, lk); error = EBUSY; break; } #ifdef ADAPTIVE_LOCKMGRS /* * If the owner is running on another CPU, spin until * the owner stops running or the state of the lock * changes. We need a double-state handle here * because for a failed acquisition the lock can be * either held in exclusive mode or shared mode * (for the writer starvation avoidance technique). */ if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && LK_HOLDER(x) != LK_KERNPROC) { owner = (struct thread *)LK_HOLDER(x); if (LOCK_LOG_TEST(&lk->lock_object, 0)) CTR3(KTR_LOCK, "%s: spinning on %p held by %p", __func__, lk, owner); /* * If we are holding also an interlock drop it * in order to avoid a deadlock if the lockmgr * owner is adaptively spinning on the * interlock itself. */ if (flags & LK_INTERLOCK) { class->lc_unlock(ilk); flags &= ~LK_INTERLOCK; } GIANT_SAVE(); while (LK_HOLDER(lk->lk_lock) == (uintptr_t)owner && TD_IS_RUNNING(owner)) cpu_spinwait(); GIANT_RESTORE(); continue; } else if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) != 0 && LK_SHARERS(x) && - spintries < alk_retries) { + spintries < ALK_RETRIES) { if (flags & LK_INTERLOCK) { class->lc_unlock(ilk); flags &= ~LK_INTERLOCK; } GIANT_SAVE(); spintries++; - for (i = 0; i < alk_loops; i++) { + for (i = 0; i < ALK_LOOPS; i++) { if (LOCK_LOG_TEST(&lk->lock_object, 0)) CTR4(KTR_LOCK, "%s: shared spinning on %p with %u and %u", __func__, lk, spintries, i); x = lk->lk_lock; if ((x & LK_SHARE) == 0 || LK_CAN_SHARE(x) != 0) break; cpu_spinwait(); } GIANT_RESTORE(); - if (i != alk_loops) + if (i != ALK_LOOPS) continue; } #endif /* * Acquire the sleepqueue chain lock because we * probabilly will need to manipulate waiters flags. */ sleepq_lock(&lk->lock_object); x = lk->lk_lock; /* * if the lock can be acquired in shared mode, try * again. */ if (LK_CAN_SHARE(x)) { sleepq_release(&lk->lock_object); continue; } #ifdef ADAPTIVE_LOCKMGRS /* * The current lock owner might have started executing * on another CPU (or the lock could have changed * owner) while we were waiting on the turnstile * chain lock. If so, drop the turnstile lock and try * again. */ if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && LK_HOLDER(x) != LK_KERNPROC) { owner = (struct thread *)LK_HOLDER(x); if (TD_IS_RUNNING(owner)) { sleepq_release(&lk->lock_object); continue; } } #endif /* * Try to set the LK_SHARED_WAITERS flag. If we fail, * loop back and retry. */ if ((x & LK_SHARED_WAITERS) == 0) { if (!atomic_cmpset_acq_ptr(&lk->lk_lock, x, x | LK_SHARED_WAITERS)) { sleepq_release(&lk->lock_object); continue; } LOCK_LOG2(lk, "%s: %p set shared waiters flag", __func__, lk); } /* * As far as we have been unable to acquire the * shared lock and the shared waiters flag is set, * we will sleep. */ error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo, SQ_SHARED_QUEUE); flags &= ~LK_INTERLOCK; if (error) { LOCK_LOG3(lk, "%s: interrupted sleep for %p with %d", __func__, lk, error); break; } LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", __func__, lk); } if (error == 0) { lock_profile_obtain_lock_success(&lk->lock_object, contested, waittime, file, line); LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, file, line); WITNESS_LOCK(&lk->lock_object, LK_TRYWIT(flags), file, line); TD_LOCKS_INC(curthread); TD_SLOCKS_INC(curthread); STACK_SAVE(lk); } break; case LK_UPGRADE: _lockmgr_assert(lk, KA_SLOCKED, file, line); v = lk->lk_lock; x = v & LK_ALL_WAITERS; v &= LK_EXCLUSIVE_SPINNERS; /* * Try to switch from one shared lock to an exclusive one. * We need to preserve waiters flags during the operation. */ if (atomic_cmpset_ptr(&lk->lk_lock, LK_SHARERS_LOCK(1) | x | v, tid | x)) { LOCK_LOG_LOCK("XUPGRADE", &lk->lock_object, 0, 0, file, line); WITNESS_UPGRADE(&lk->lock_object, LOP_EXCLUSIVE | LK_TRYWIT(flags), file, line); TD_SLOCKS_DEC(curthread); break; } /* * We have been unable to succeed in upgrading, so just * give up the shared lock. */ wakeup_swapper |= wakeupshlk(lk, file, line); /* FALLTHROUGH */ case LK_EXCLUSIVE: if (LK_CAN_WITNESS(flags)) WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | LOP_EXCLUSIVE, file, line, ilk); /* * If curthread already holds the lock and this one is * allowed to recurse, simply recurse on it. */ if (lockmgr_xlocked(lk)) { if ((flags & LK_CANRECURSE) == 0 && (lk->lock_object.lo_flags & LO_RECURSABLE) == 0) { /* * If the lock is expected to not panic just * give up and return. */ if (LK_TRYOP(flags)) { LOCK_LOG2(lk, "%s: %p fails the try operation", __func__, lk); error = EBUSY; break; } if (flags & LK_INTERLOCK) class->lc_unlock(ilk); panic("%s: recursing on non recursive lockmgr %s @ %s:%d\n", __func__, iwmesg, file, line); } lk->lk_recurse++; LOCK_LOG2(lk, "%s: %p recursing", __func__, lk); LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, lk->lk_recurse, file, line); WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | LK_TRYWIT(flags), file, line); TD_LOCKS_INC(curthread); break; } while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) { lock_profile_obtain_lock_failed(&lk->lock_object, &contested, &waittime); /* * If the lock is expected to not sleep just give up * and return. */ if (LK_TRYOP(flags)) { LOCK_LOG2(lk, "%s: %p fails the try operation", __func__, lk); error = EBUSY; break; } #ifdef ADAPTIVE_LOCKMGRS /* * If the owner is running on another CPU, spin until * the owner stops running or the state of the lock * changes. */ x = lk->lk_lock; if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && LK_HOLDER(x) != LK_KERNPROC) { owner = (struct thread *)LK_HOLDER(x); if (LOCK_LOG_TEST(&lk->lock_object, 0)) CTR3(KTR_LOCK, "%s: spinning on %p held by %p", __func__, lk, owner); /* * If we are holding also an interlock drop it * in order to avoid a deadlock if the lockmgr * owner is adaptively spinning on the * interlock itself. */ if (flags & LK_INTERLOCK) { class->lc_unlock(ilk); flags &= ~LK_INTERLOCK; } GIANT_SAVE(); while (LK_HOLDER(lk->lk_lock) == (uintptr_t)owner && TD_IS_RUNNING(owner)) cpu_spinwait(); GIANT_RESTORE(); continue; } else if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) != 0 && LK_SHARERS(x) && - spintries < alk_retries) { + spintries < ALK_RETRIES) { if ((x & LK_EXCLUSIVE_SPINNERS) == 0 && !atomic_cmpset_ptr(&lk->lk_lock, x, x | LK_EXCLUSIVE_SPINNERS)) continue; if (flags & LK_INTERLOCK) { class->lc_unlock(ilk); flags &= ~LK_INTERLOCK; } GIANT_SAVE(); spintries++; - for (i = 0; i < alk_loops; i++) { + for (i = 0; i < ALK_LOOPS; i++) { if (LOCK_LOG_TEST(&lk->lock_object, 0)) CTR4(KTR_LOCK, "%s: shared spinning on %p with %u and %u", __func__, lk, spintries, i); if ((lk->lk_lock & LK_EXCLUSIVE_SPINNERS) == 0) break; cpu_spinwait(); } GIANT_RESTORE(); - if (i != alk_loops) + if (i != ALK_LOOPS) continue; } #endif /* * Acquire the sleepqueue chain lock because we * probabilly will need to manipulate waiters flags. */ sleepq_lock(&lk->lock_object); x = lk->lk_lock; /* * if the lock has been released while we spun on * the sleepqueue chain lock just try again. */ if (x == LK_UNLOCKED) { sleepq_release(&lk->lock_object); continue; } #ifdef ADAPTIVE_LOCKMGRS /* * The current lock owner might have started executing * on another CPU (or the lock could have changed * owner) while we were waiting on the turnstile * chain lock. If so, drop the turnstile lock and try * again. */ if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && LK_HOLDER(x) != LK_KERNPROC) { owner = (struct thread *)LK_HOLDER(x); if (TD_IS_RUNNING(owner)) { sleepq_release(&lk->lock_object); continue; } } #endif /* * The lock can be in the state where there is a * pending queue of waiters, but still no owner. * This happens when the lock is contested and an * owner is going to claim the lock. * If curthread is the one successfully acquiring it * claim lock ownership and return, preserving waiters * flags. */ v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); if ((x & ~v) == LK_UNLOCKED) { v &= ~LK_EXCLUSIVE_SPINNERS; if (atomic_cmpset_acq_ptr(&lk->lk_lock, x, tid | v)) { sleepq_release(&lk->lock_object); LOCK_LOG2(lk, "%s: %p claimed by a new writer", __func__, lk); break; } sleepq_release(&lk->lock_object); continue; } /* * Try to set the LK_EXCLUSIVE_WAITERS flag. If we * fail, loop back and retry. */ if ((x & LK_EXCLUSIVE_WAITERS) == 0) { if (!atomic_cmpset_ptr(&lk->lk_lock, x, x | LK_EXCLUSIVE_WAITERS)) { sleepq_release(&lk->lock_object); continue; } LOCK_LOG2(lk, "%s: %p set excl waiters flag", __func__, lk); } /* * As far as we have been unable to acquire the * exclusive lock and the exclusive waiters flag * is set, we will sleep. */ error = sleeplk(lk, flags, ilk, iwmesg, ipri, itimo, SQ_EXCLUSIVE_QUEUE); flags &= ~LK_INTERLOCK; if (error) { LOCK_LOG3(lk, "%s: interrupted sleep for %p with %d", __func__, lk, error); break; } LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", __func__, lk); } if (error == 0) { lock_profile_obtain_lock_success(&lk->lock_object, contested, waittime, file, line); LOCK_LOG_LOCK("XLOCK", &lk->lock_object, 0, lk->lk_recurse, file, line); WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | LK_TRYWIT(flags), file, line); TD_LOCKS_INC(curthread); STACK_SAVE(lk); } break; case LK_DOWNGRADE: _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, file, line); LOCK_LOG_LOCK("XDOWNGRADE", &lk->lock_object, 0, 0, file, line); WITNESS_DOWNGRADE(&lk->lock_object, 0, file, line); TD_SLOCKS_INC(curthread); /* * In order to preserve waiters flags, just spin. */ for (;;) { x = lk->lk_lock; MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); x &= LK_ALL_WAITERS; if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x, LK_SHARERS_LOCK(1) | x)) break; cpu_spinwait(); } break; case LK_RELEASE: _lockmgr_assert(lk, KA_LOCKED, file, line); x = lk->lk_lock; if ((x & LK_SHARE) == 0) { /* * As first option, treact the lock as if it has not * any waiter. * Fix-up the tid var if the lock has been disowned. */ if (LK_HOLDER(x) == LK_KERNPROC) tid = LK_KERNPROC; else { WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line); TD_LOCKS_DEC(curthread); } LOCK_LOG_LOCK("XUNLOCK", &lk->lock_object, 0, lk->lk_recurse, file, line); /* * The lock is held in exclusive mode. * If the lock is recursed also, then unrecurse it. */ if (lockmgr_xlocked(lk) && lockmgr_recursed(lk)) { LOCK_LOG2(lk, "%s: %p unrecursing", __func__, lk); lk->lk_recurse--; break; } if (tid != LK_KERNPROC) lock_profile_release_lock(&lk->lock_object); if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid, LK_UNLOCKED)) break; sleepq_lock(&lk->lock_object); x = lk->lk_lock; v = LK_UNLOCKED; /* * If the lock has exclusive waiters, give them * preference in order to avoid deadlock with * shared runners up. * If interruptible sleeps left the exclusive queue * empty avoid a starvation for the threads sleeping * on the shared queue by giving them precedence * and cleaning up the exclusive waiters bit anyway. * Please note that lk_exslpfail count may be lying * about the real number of waiters with the * LK_SLEEPFAIL flag on because they may be used in * conjuction with interruptible sleeps so * lk_exslpfail might be considered an 'upper limit' * bound, including the edge cases. */ MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); realexslp = sleepq_sleepcnt(&lk->lock_object, SQ_EXCLUSIVE_QUEUE); if ((x & LK_EXCLUSIVE_WAITERS) != 0 && realexslp != 0) { if (lk->lk_exslpfail < realexslp) { lk->lk_exslpfail = 0; queue = SQ_EXCLUSIVE_QUEUE; v |= (x & LK_SHARED_WAITERS); } else { lk->lk_exslpfail = 0; LOCK_LOG2(lk, "%s: %p has only LK_SLEEPFAIL sleepers", __func__, lk); LOCK_LOG2(lk, "%s: %p waking up threads on the exclusive queue", __func__, lk); wakeup_swapper = sleepq_broadcast(&lk->lock_object, SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE); queue = SQ_SHARED_QUEUE; } } else { /* * Exclusive waiters sleeping with LK_SLEEPFAIL * on and using interruptible sleeps/timeout * may have left spourious lk_exslpfail counts * on, so clean it up anyway. */ lk->lk_exslpfail = 0; queue = SQ_SHARED_QUEUE; } LOCK_LOG3(lk, "%s: %p waking up threads on the %s queue", __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" : "exclusive"); atomic_store_rel_ptr(&lk->lk_lock, v); wakeup_swapper |= sleepq_broadcast(&lk->lock_object, SLEEPQ_LK, 0, queue); sleepq_release(&lk->lock_object); break; } else wakeup_swapper = wakeupshlk(lk, file, line); break; case LK_DRAIN: if (LK_CAN_WITNESS(flags)) WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER | LOP_EXCLUSIVE, file, line, ilk); /* * Trying to drain a lock we already own will result in a * deadlock. */ if (lockmgr_xlocked(lk)) { if (flags & LK_INTERLOCK) class->lc_unlock(ilk); panic("%s: draining %s with the lock held @ %s:%d\n", __func__, iwmesg, file, line); } while (!atomic_cmpset_acq_ptr(&lk->lk_lock, LK_UNLOCKED, tid)) { lock_profile_obtain_lock_failed(&lk->lock_object, &contested, &waittime); /* * If the lock is expected to not sleep just give up * and return. */ if (LK_TRYOP(flags)) { LOCK_LOG2(lk, "%s: %p fails the try operation", __func__, lk); error = EBUSY; break; } /* * Acquire the sleepqueue chain lock because we * probabilly will need to manipulate waiters flags. */ sleepq_lock(&lk->lock_object); x = lk->lk_lock; /* * if the lock has been released while we spun on * the sleepqueue chain lock just try again. */ if (x == LK_UNLOCKED) { sleepq_release(&lk->lock_object); continue; } v = x & (LK_ALL_WAITERS | LK_EXCLUSIVE_SPINNERS); if ((x & ~v) == LK_UNLOCKED) { v = (x & ~LK_EXCLUSIVE_SPINNERS); /* * If interruptible sleeps left the exclusive * queue empty avoid a starvation for the * threads sleeping on the shared queue by * giving them precedence and cleaning up the * exclusive waiters bit anyway. * Please note that lk_exslpfail count may be * lying about the real number of waiters with * the LK_SLEEPFAIL flag on because they may * be used in conjuction with interruptible * sleeps so lk_exslpfail might be considered * an 'upper limit' bound, including the edge * cases. */ if (v & LK_EXCLUSIVE_WAITERS) { queue = SQ_EXCLUSIVE_QUEUE; v &= ~LK_EXCLUSIVE_WAITERS; } else { /* * Exclusive waiters sleeping with * LK_SLEEPFAIL on and using * interruptible sleeps/timeout may * have left spourious lk_exslpfail * counts on, so clean it up anyway. */ MPASS(v & LK_SHARED_WAITERS); lk->lk_exslpfail = 0; queue = SQ_SHARED_QUEUE; v &= ~LK_SHARED_WAITERS; } if (queue == SQ_EXCLUSIVE_QUEUE) { realexslp = sleepq_sleepcnt(&lk->lock_object, SQ_EXCLUSIVE_QUEUE); if (lk->lk_exslpfail >= realexslp) { lk->lk_exslpfail = 0; queue = SQ_SHARED_QUEUE; v &= ~LK_SHARED_WAITERS; if (realexslp != 0) { LOCK_LOG2(lk, "%s: %p has only LK_SLEEPFAIL sleepers", __func__, lk); LOCK_LOG2(lk, "%s: %p waking up threads on the exclusive queue", __func__, lk); wakeup_swapper = sleepq_broadcast( &lk->lock_object, SLEEPQ_LK, 0, SQ_EXCLUSIVE_QUEUE); } } else lk->lk_exslpfail = 0; } if (!atomic_cmpset_ptr(&lk->lk_lock, x, v)) { sleepq_release(&lk->lock_object); continue; } LOCK_LOG3(lk, "%s: %p waking up all threads on the %s queue", __func__, lk, queue == SQ_SHARED_QUEUE ? "shared" : "exclusive"); wakeup_swapper |= sleepq_broadcast( &lk->lock_object, SLEEPQ_LK, 0, queue); /* * If shared waiters have been woken up we need * to wait for one of them to acquire the lock * before to set the exclusive waiters in * order to avoid a deadlock. */ if (queue == SQ_SHARED_QUEUE) { for (v = lk->lk_lock; (v & LK_SHARE) && !LK_SHARERS(v); v = lk->lk_lock) cpu_spinwait(); } } /* * Try to set the LK_EXCLUSIVE_WAITERS flag. If we * fail, loop back and retry. */ if ((x & LK_EXCLUSIVE_WAITERS) == 0) { if (!atomic_cmpset_ptr(&lk->lk_lock, x, x | LK_EXCLUSIVE_WAITERS)) { sleepq_release(&lk->lock_object); continue; } LOCK_LOG2(lk, "%s: %p set drain waiters flag", __func__, lk); } /* * As far as we have been unable to acquire the * exclusive lock and the exclusive waiters flag * is set, we will sleep. */ if (flags & LK_INTERLOCK) { class->lc_unlock(ilk); flags &= ~LK_INTERLOCK; } GIANT_SAVE(); sleepq_add(&lk->lock_object, NULL, iwmesg, SLEEPQ_LK, SQ_EXCLUSIVE_QUEUE); sleepq_wait(&lk->lock_object, ipri & PRIMASK); GIANT_RESTORE(); LOCK_LOG2(lk, "%s: %p resuming from the sleep queue", __func__, lk); } if (error == 0) { lock_profile_obtain_lock_success(&lk->lock_object, contested, waittime, file, line); LOCK_LOG_LOCK("DRAIN", &lk->lock_object, 0, lk->lk_recurse, file, line); WITNESS_LOCK(&lk->lock_object, LOP_EXCLUSIVE | LK_TRYWIT(flags), file, line); TD_LOCKS_INC(curthread); STACK_SAVE(lk); } break; default: if (flags & LK_INTERLOCK) class->lc_unlock(ilk); panic("%s: unknown lockmgr request 0x%x\n", __func__, op); } if (flags & LK_INTERLOCK) class->lc_unlock(ilk); if (wakeup_swapper) kick_proc0(); return (error); } void _lockmgr_disown(struct lock *lk, const char *file, int line) { uintptr_t tid, x; tid = (uintptr_t)curthread; _lockmgr_assert(lk, KA_XLOCKED | KA_NOTRECURSED, file, line); /* * If the owner is already LK_KERNPROC just skip the whole operation. */ if (LK_HOLDER(lk->lk_lock) != tid) return; lock_profile_release_lock(&lk->lock_object); LOCK_LOG_LOCK("XDISOWN", &lk->lock_object, 0, 0, file, line); WITNESS_UNLOCK(&lk->lock_object, LOP_EXCLUSIVE, file, line); TD_LOCKS_DEC(curthread); STACK_SAVE(lk); /* * In order to preserve waiters flags, just spin. */ for (;;) { x = lk->lk_lock; MPASS((x & LK_EXCLUSIVE_SPINNERS) == 0); x &= LK_ALL_WAITERS; if (atomic_cmpset_rel_ptr(&lk->lk_lock, tid | x, LK_KERNPROC | x)) return; cpu_spinwait(); } } void lockmgr_printinfo(struct lock *lk) { struct thread *td; uintptr_t x; if (lk->lk_lock == LK_UNLOCKED) printf("lock type %s: UNLOCKED\n", lk->lock_object.lo_name); else if (lk->lk_lock & LK_SHARE) printf("lock type %s: SHARED (count %ju)\n", lk->lock_object.lo_name, (uintmax_t)LK_SHARERS(lk->lk_lock)); else { td = lockmgr_xholder(lk); printf("lock type %s: EXCL by thread %p (pid %d)\n", lk->lock_object.lo_name, td, td->td_proc->p_pid); } x = lk->lk_lock; if (x & LK_EXCLUSIVE_WAITERS) printf(" with exclusive waiters pending\n"); if (x & LK_SHARED_WAITERS) printf(" with shared waiters pending\n"); if (x & LK_EXCLUSIVE_SPINNERS) printf(" with exclusive spinners pending\n"); STACK_PRINT(lk); } int lockstatus(struct lock *lk) { uintptr_t v, x; int ret; ret = LK_SHARED; x = lk->lk_lock; v = LK_HOLDER(x); if ((x & LK_SHARE) == 0) { if (v == (uintptr_t)curthread || v == LK_KERNPROC) ret = LK_EXCLUSIVE; else ret = LK_EXCLOTHER; } else if (x == LK_UNLOCKED) ret = 0; return (ret); } #ifdef INVARIANT_SUPPORT FEATURE(invariant_support, "Support for modules compiled with INVARIANTS option"); #ifndef INVARIANTS #undef _lockmgr_assert #endif void _lockmgr_assert(struct lock *lk, int what, const char *file, int line) { int slocked = 0; if (panicstr != NULL) return; switch (what) { case KA_SLOCKED: case KA_SLOCKED | KA_NOTRECURSED: case KA_SLOCKED | KA_RECURSED: slocked = 1; case KA_LOCKED: case KA_LOCKED | KA_NOTRECURSED: case KA_LOCKED | KA_RECURSED: #ifdef WITNESS /* * We cannot trust WITNESS if the lock is held in exclusive * mode and a call to lockmgr_disown() happened. * Workaround this skipping the check if the lock is held in * exclusive mode even for the KA_LOCKED case. */ if (slocked || (lk->lk_lock & LK_SHARE)) { witness_assert(&lk->lock_object, what, file, line); break; } #endif if (lk->lk_lock == LK_UNLOCKED || ((lk->lk_lock & LK_SHARE) == 0 && (slocked || (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk))))) panic("Lock %s not %slocked @ %s:%d\n", lk->lock_object.lo_name, slocked ? "share" : "", file, line); if ((lk->lk_lock & LK_SHARE) == 0) { if (lockmgr_recursed(lk)) { if (what & KA_NOTRECURSED) panic("Lock %s recursed @ %s:%d\n", lk->lock_object.lo_name, file, line); } else if (what & KA_RECURSED) panic("Lock %s not recursed @ %s:%d\n", lk->lock_object.lo_name, file, line); } break; case KA_XLOCKED: case KA_XLOCKED | KA_NOTRECURSED: case KA_XLOCKED | KA_RECURSED: if (!lockmgr_xlocked(lk) && !lockmgr_disowned(lk)) panic("Lock %s not exclusively locked @ %s:%d\n", lk->lock_object.lo_name, file, line); if (lockmgr_recursed(lk)) { if (what & KA_NOTRECURSED) panic("Lock %s recursed @ %s:%d\n", lk->lock_object.lo_name, file, line); } else if (what & KA_RECURSED) panic("Lock %s not recursed @ %s:%d\n", lk->lock_object.lo_name, file, line); break; case KA_UNLOCKED: if (lockmgr_xlocked(lk) || lockmgr_disowned(lk)) panic("Lock %s exclusively locked @ %s:%d\n", lk->lock_object.lo_name, file, line); break; default: panic("Unknown lockmgr assertion: %d @ %s:%d\n", what, file, line); } } #endif #ifdef DDB int lockmgr_chain(struct thread *td, struct thread **ownerp) { struct lock *lk; lk = td->td_wchan; if (LOCK_CLASS(&lk->lock_object) != &lock_class_lockmgr) return (0); db_printf("blocked on lockmgr %s", lk->lock_object.lo_name); if (lk->lk_lock & LK_SHARE) db_printf("SHARED (count %ju)\n", (uintmax_t)LK_SHARERS(lk->lk_lock)); else db_printf("EXCL\n"); *ownerp = lockmgr_xholder(lk); return (1); } static void db_show_lockmgr(struct lock_object *lock) { struct thread *td; struct lock *lk; lk = (struct lock *)lock; db_printf(" state: "); if (lk->lk_lock == LK_UNLOCKED) db_printf("UNLOCKED\n"); else if (lk->lk_lock & LK_SHARE) db_printf("SLOCK: %ju\n", (uintmax_t)LK_SHARERS(lk->lk_lock)); else { td = lockmgr_xholder(lk); if (td == (struct thread *)LK_KERNPROC) db_printf("XLOCK: LK_KERNPROC\n"); else db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td, td->td_tid, td->td_proc->p_pid, td->td_proc->p_comm); if (lockmgr_recursed(lk)) db_printf(" recursed: %d\n", lk->lk_recurse); } db_printf(" waiters: "); switch (lk->lk_lock & LK_ALL_WAITERS) { case LK_SHARED_WAITERS: db_printf("shared\n"); break; case LK_EXCLUSIVE_WAITERS: db_printf("exclusive\n"); break; case LK_ALL_WAITERS: db_printf("shared and exclusive\n"); break; default: db_printf("none\n"); } db_printf(" spinners: "); if (lk->lk_lock & LK_EXCLUSIVE_SPINNERS) db_printf("exclusive\n"); else db_printf("none\n"); } #endif Index: stable/9/sys/kern/kern_rwlock.c =================================================================== --- stable/9/sys/kern/kern_rwlock.c (revision 226254) +++ stable/9/sys/kern/kern_rwlock.c (revision 226255) @@ -1,1126 +1,1123 @@ /*- * Copyright (c) 2006 John Baldwin * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. Neither the name of the author nor the names of any co-contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ /* * Machine independent bits of reader/writer lock implementation. */ #include __FBSDID("$FreeBSD$"); #include "opt_ddb.h" #include "opt_kdtrace.h" #include "opt_no_adaptive_rwlocks.h" #include #include #include #include #include #include #include #include #include #include #include #if defined(SMP) && !defined(NO_ADAPTIVE_RWLOCKS) #define ADAPTIVE_RWLOCKS #endif #ifdef ADAPTIVE_RWLOCKS -static int rowner_retries = 10; -static int rowner_loops = 10000; -SYSCTL_NODE(_debug, OID_AUTO, rwlock, CTLFLAG_RD, NULL, "rwlock debugging"); -SYSCTL_INT(_debug_rwlock, OID_AUTO, retry, CTLFLAG_RW, &rowner_retries, 0, ""); -SYSCTL_INT(_debug_rwlock, OID_AUTO, loops, CTLFLAG_RW, &rowner_loops, 0, ""); +#define ROWNER_RETRIES 10 +#define ROWNER_LOOPS 10000 #endif #ifdef DDB #include static void db_show_rwlock(struct lock_object *lock); #endif static void assert_rw(struct lock_object *lock, int what); static void lock_rw(struct lock_object *lock, int how); #ifdef KDTRACE_HOOKS static int owner_rw(struct lock_object *lock, struct thread **owner); #endif static int unlock_rw(struct lock_object *lock); struct lock_class lock_class_rw = { .lc_name = "rw", .lc_flags = LC_SLEEPLOCK | LC_RECURSABLE | LC_UPGRADABLE, .lc_assert = assert_rw, #ifdef DDB .lc_ddb_show = db_show_rwlock, #endif .lc_lock = lock_rw, .lc_unlock = unlock_rw, #ifdef KDTRACE_HOOKS .lc_owner = owner_rw, #endif }; /* * Return a pointer to the owning thread if the lock is write-locked or * NULL if the lock is unlocked or read-locked. */ #define rw_wowner(rw) \ ((rw)->rw_lock & RW_LOCK_READ ? NULL : \ (struct thread *)RW_OWNER((rw)->rw_lock)) /* * Returns if a write owner is recursed. Write ownership is not assured * here and should be previously checked. */ #define rw_recursed(rw) ((rw)->rw_recurse != 0) /* * Return true if curthread helds the lock. */ #define rw_wlocked(rw) (rw_wowner((rw)) == curthread) /* * Return a pointer to the owning thread for this lock who should receive * any priority lent by threads that block on this lock. Currently this * is identical to rw_wowner(). */ #define rw_owner(rw) rw_wowner(rw) #ifndef INVARIANTS #define _rw_assert(rw, what, file, line) #endif void assert_rw(struct lock_object *lock, int what) { rw_assert((struct rwlock *)lock, what); } void lock_rw(struct lock_object *lock, int how) { struct rwlock *rw; rw = (struct rwlock *)lock; if (how) rw_wlock(rw); else rw_rlock(rw); } int unlock_rw(struct lock_object *lock) { struct rwlock *rw; rw = (struct rwlock *)lock; rw_assert(rw, RA_LOCKED | LA_NOTRECURSED); if (rw->rw_lock & RW_LOCK_READ) { rw_runlock(rw); return (0); } else { rw_wunlock(rw); return (1); } } #ifdef KDTRACE_HOOKS int owner_rw(struct lock_object *lock, struct thread **owner) { struct rwlock *rw = (struct rwlock *)lock; uintptr_t x = rw->rw_lock; *owner = rw_wowner(rw); return ((x & RW_LOCK_READ) != 0 ? (RW_READERS(x) != 0) : (*owner != NULL)); } #endif void rw_init_flags(struct rwlock *rw, const char *name, int opts) { int flags; MPASS((opts & ~(RW_DUPOK | RW_NOPROFILE | RW_NOWITNESS | RW_QUIET | RW_RECURSE)) == 0); ASSERT_ATOMIC_LOAD_PTR(rw->rw_lock, ("%s: rw_lock not aligned for %s: %p", __func__, name, &rw->rw_lock)); flags = LO_UPGRADABLE; if (opts & RW_DUPOK) flags |= LO_DUPOK; if (opts & RW_NOPROFILE) flags |= LO_NOPROFILE; if (!(opts & RW_NOWITNESS)) flags |= LO_WITNESS; if (opts & RW_RECURSE) flags |= LO_RECURSABLE; if (opts & RW_QUIET) flags |= LO_QUIET; rw->rw_lock = RW_UNLOCKED; rw->rw_recurse = 0; lock_init(&rw->lock_object, &lock_class_rw, name, NULL, flags); } void rw_destroy(struct rwlock *rw) { KASSERT(rw->rw_lock == RW_UNLOCKED, ("rw lock %p not unlocked", rw)); KASSERT(rw->rw_recurse == 0, ("rw lock %p still recursed", rw)); rw->rw_lock = RW_DESTROYED; lock_destroy(&rw->lock_object); } void rw_sysinit(void *arg) { struct rw_args *args = arg; rw_init(args->ra_rw, args->ra_desc); } void rw_sysinit_flags(void *arg) { struct rw_args_flags *args = arg; rw_init_flags(args->ra_rw, args->ra_desc, args->ra_flags); } int rw_wowned(struct rwlock *rw) { return (rw_wowner(rw) == curthread); } void _rw_wlock(struct rwlock *rw, const char *file, int line) { MPASS(curthread != NULL); KASSERT(rw->rw_lock != RW_DESTROYED, ("rw_wlock() of destroyed rwlock @ %s:%d", file, line)); WITNESS_CHECKORDER(&rw->lock_object, LOP_NEWORDER | LOP_EXCLUSIVE, file, line, NULL); __rw_wlock(rw, curthread, file, line); LOCK_LOG_LOCK("WLOCK", &rw->lock_object, 0, rw->rw_recurse, file, line); WITNESS_LOCK(&rw->lock_object, LOP_EXCLUSIVE, file, line); curthread->td_locks++; } int _rw_try_wlock(struct rwlock *rw, const char *file, int line) { int rval; KASSERT(rw->rw_lock != RW_DESTROYED, ("rw_try_wlock() of destroyed rwlock @ %s:%d", file, line)); if (rw_wlocked(rw) && (rw->lock_object.lo_flags & LO_RECURSABLE) != 0) { rw->rw_recurse++; rval = 1; } else rval = atomic_cmpset_acq_ptr(&rw->rw_lock, RW_UNLOCKED, (uintptr_t)curthread); LOCK_LOG_TRY("WLOCK", &rw->lock_object, 0, rval, file, line); if (rval) { WITNESS_LOCK(&rw->lock_object, LOP_EXCLUSIVE | LOP_TRYLOCK, file, line); curthread->td_locks++; } return (rval); } void _rw_wunlock(struct rwlock *rw, const char *file, int line) { MPASS(curthread != NULL); KASSERT(rw->rw_lock != RW_DESTROYED, ("rw_wunlock() of destroyed rwlock @ %s:%d", file, line)); _rw_assert(rw, RA_WLOCKED, file, line); curthread->td_locks--; WITNESS_UNLOCK(&rw->lock_object, LOP_EXCLUSIVE, file, line); LOCK_LOG_LOCK("WUNLOCK", &rw->lock_object, 0, rw->rw_recurse, file, line); if (!rw_recursed(rw)) LOCKSTAT_PROFILE_RELEASE_LOCK(LS_RW_WUNLOCK_RELEASE, rw); __rw_wunlock(rw, curthread, file, line); } /* * Determines whether a new reader can acquire a lock. Succeeds if the * reader already owns a read lock and the lock is locked for read to * prevent deadlock from reader recursion. Also succeeds if the lock * is unlocked and has no writer waiters or spinners. Failing otherwise * prioritizes writers before readers. */ #define RW_CAN_READ(_rw) \ ((curthread->td_rw_rlocks && (_rw) & RW_LOCK_READ) || ((_rw) & \ (RW_LOCK_READ | RW_LOCK_WRITE_WAITERS | RW_LOCK_WRITE_SPINNER)) == \ RW_LOCK_READ) void _rw_rlock(struct rwlock *rw, const char *file, int line) { struct turnstile *ts; #ifdef ADAPTIVE_RWLOCKS volatile struct thread *owner; int spintries = 0; int i; #endif #ifdef LOCK_PROFILING uint64_t waittime = 0; int contested = 0; #endif uintptr_t v; #ifdef KDTRACE_HOOKS uint64_t spin_cnt = 0; uint64_t sleep_cnt = 0; int64_t sleep_time = 0; #endif KASSERT(rw->rw_lock != RW_DESTROYED, ("rw_rlock() of destroyed rwlock @ %s:%d", file, line)); KASSERT(rw_wowner(rw) != curthread, ("%s (%s): wlock already held @ %s:%d", __func__, rw->lock_object.lo_name, file, line)); WITNESS_CHECKORDER(&rw->lock_object, LOP_NEWORDER, file, line, NULL); for (;;) { #ifdef KDTRACE_HOOKS spin_cnt++; #endif /* * Handle the easy case. If no other thread has a write * lock, then try to bump up the count of read locks. Note * that we have to preserve the current state of the * RW_LOCK_WRITE_WAITERS flag. If we fail to acquire a * read lock, then rw_lock must have changed, so restart * the loop. Note that this handles the case of a * completely unlocked rwlock since such a lock is encoded * as a read lock with no waiters. */ v = rw->rw_lock; if (RW_CAN_READ(v)) { /* * The RW_LOCK_READ_WAITERS flag should only be set * if the lock has been unlocked and write waiters * were present. */ if (atomic_cmpset_acq_ptr(&rw->rw_lock, v, v + RW_ONE_READER)) { if (LOCK_LOG_TEST(&rw->lock_object, 0)) CTR4(KTR_LOCK, "%s: %p succeed %p -> %p", __func__, rw, (void *)v, (void *)(v + RW_ONE_READER)); break; } continue; } lock_profile_obtain_lock_failed(&rw->lock_object, &contested, &waittime); #ifdef ADAPTIVE_RWLOCKS /* * If the owner is running on another CPU, spin until * the owner stops running or the state of the lock * changes. */ if ((v & RW_LOCK_READ) == 0) { owner = (struct thread *)RW_OWNER(v); if (TD_IS_RUNNING(owner)) { if (LOCK_LOG_TEST(&rw->lock_object, 0)) CTR3(KTR_LOCK, "%s: spinning on %p held by %p", __func__, rw, owner); while ((struct thread*)RW_OWNER(rw->rw_lock) == owner && TD_IS_RUNNING(owner)) { cpu_spinwait(); #ifdef KDTRACE_HOOKS spin_cnt++; #endif } continue; } - } else if (spintries < rowner_retries) { + } else if (spintries < ROWNER_RETRIES) { spintries++; - for (i = 0; i < rowner_loops; i++) { + for (i = 0; i < ROWNER_LOOPS; i++) { v = rw->rw_lock; if ((v & RW_LOCK_READ) == 0 || RW_CAN_READ(v)) break; cpu_spinwait(); } - if (i != rowner_loops) + if (i != ROWNER_LOOPS) continue; } #endif /* * Okay, now it's the hard case. Some other thread already * has a write lock or there are write waiters present, * acquire the turnstile lock so we can begin the process * of blocking. */ ts = turnstile_trywait(&rw->lock_object); /* * The lock might have been released while we spun, so * recheck its state and restart the loop if needed. */ v = rw->rw_lock; if (RW_CAN_READ(v)) { turnstile_cancel(ts); continue; } #ifdef ADAPTIVE_RWLOCKS /* * The current lock owner might have started executing * on another CPU (or the lock could have changed * owners) while we were waiting on the turnstile * chain lock. If so, drop the turnstile lock and try * again. */ if ((v & RW_LOCK_READ) == 0) { owner = (struct thread *)RW_OWNER(v); if (TD_IS_RUNNING(owner)) { turnstile_cancel(ts); continue; } } #endif /* * The lock is held in write mode or it already has waiters. */ MPASS(!RW_CAN_READ(v)); /* * If the RW_LOCK_READ_WAITERS flag is already set, then * we can go ahead and block. If it is not set then try * to set it. If we fail to set it drop the turnstile * lock and restart the loop. */ if (!(v & RW_LOCK_READ_WAITERS)) { if (!atomic_cmpset_ptr(&rw->rw_lock, v, v | RW_LOCK_READ_WAITERS)) { turnstile_cancel(ts); continue; } if (LOCK_LOG_TEST(&rw->lock_object, 0)) CTR2(KTR_LOCK, "%s: %p set read waiters flag", __func__, rw); } /* * We were unable to acquire the lock and the read waiters * flag is set, so we must block on the turnstile. */ if (LOCK_LOG_TEST(&rw->lock_object, 0)) CTR2(KTR_LOCK, "%s: %p blocking on turnstile", __func__, rw); #ifdef KDTRACE_HOOKS sleep_time -= lockstat_nsecs(); #endif turnstile_wait(ts, rw_owner(rw), TS_SHARED_QUEUE); #ifdef KDTRACE_HOOKS sleep_time += lockstat_nsecs(); sleep_cnt++; #endif if (LOCK_LOG_TEST(&rw->lock_object, 0)) CTR2(KTR_LOCK, "%s: %p resuming from turnstile", __func__, rw); } /* * TODO: acquire "owner of record" here. Here be turnstile dragons * however. turnstiles don't like owners changing between calls to * turnstile_wait() currently. */ LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_RW_RLOCK_ACQUIRE, rw, contested, waittime, file, line); LOCK_LOG_LOCK("RLOCK", &rw->lock_object, 0, 0, file, line); WITNESS_LOCK(&rw->lock_object, 0, file, line); curthread->td_locks++; curthread->td_rw_rlocks++; #ifdef KDTRACE_HOOKS if (sleep_time) LOCKSTAT_RECORD1(LS_RW_RLOCK_BLOCK, rw, sleep_time); /* * Record only the loops spinning and not sleeping. */ if (spin_cnt > sleep_cnt) LOCKSTAT_RECORD1(LS_RW_RLOCK_SPIN, rw, (spin_cnt - sleep_cnt)); #endif } int _rw_try_rlock(struct rwlock *rw, const char *file, int line) { uintptr_t x; for (;;) { x = rw->rw_lock; KASSERT(rw->rw_lock != RW_DESTROYED, ("rw_try_rlock() of destroyed rwlock @ %s:%d", file, line)); if (!(x & RW_LOCK_READ)) break; if (atomic_cmpset_acq_ptr(&rw->rw_lock, x, x + RW_ONE_READER)) { LOCK_LOG_TRY("RLOCK", &rw->lock_object, 0, 1, file, line); WITNESS_LOCK(&rw->lock_object, LOP_TRYLOCK, file, line); curthread->td_locks++; curthread->td_rw_rlocks++; return (1); } } LOCK_LOG_TRY("RLOCK", &rw->lock_object, 0, 0, file, line); return (0); } void _rw_runlock(struct rwlock *rw, const char *file, int line) { struct turnstile *ts; uintptr_t x, v, queue; KASSERT(rw->rw_lock != RW_DESTROYED, ("rw_runlock() of destroyed rwlock @ %s:%d", file, line)); _rw_assert(rw, RA_RLOCKED, file, line); curthread->td_locks--; curthread->td_rw_rlocks--; WITNESS_UNLOCK(&rw->lock_object, 0, file, line); LOCK_LOG_LOCK("RUNLOCK", &rw->lock_object, 0, 0, file, line); /* TODO: drop "owner of record" here. */ for (;;) { /* * See if there is more than one read lock held. If so, * just drop one and return. */ x = rw->rw_lock; if (RW_READERS(x) > 1) { if (atomic_cmpset_rel_ptr(&rw->rw_lock, x, x - RW_ONE_READER)) { if (LOCK_LOG_TEST(&rw->lock_object, 0)) CTR4(KTR_LOCK, "%s: %p succeeded %p -> %p", __func__, rw, (void *)x, (void *)(x - RW_ONE_READER)); break; } continue; } /* * If there aren't any waiters for a write lock, then try * to drop it quickly. */ if (!(x & RW_LOCK_WAITERS)) { MPASS((x & ~RW_LOCK_WRITE_SPINNER) == RW_READERS_LOCK(1)); if (atomic_cmpset_rel_ptr(&rw->rw_lock, x, RW_UNLOCKED)) { if (LOCK_LOG_TEST(&rw->lock_object, 0)) CTR2(KTR_LOCK, "%s: %p last succeeded", __func__, rw); break; } continue; } /* * Ok, we know we have waiters and we think we are the * last reader, so grab the turnstile lock. */ turnstile_chain_lock(&rw->lock_object); v = rw->rw_lock & (RW_LOCK_WAITERS | RW_LOCK_WRITE_SPINNER); MPASS(v & RW_LOCK_WAITERS); /* * Try to drop our lock leaving the lock in a unlocked * state. * * If you wanted to do explicit lock handoff you'd have to * do it here. You'd also want to use turnstile_signal() * and you'd have to handle the race where a higher * priority thread blocks on the write lock before the * thread you wakeup actually runs and have the new thread * "steal" the lock. For now it's a lot simpler to just * wakeup all of the waiters. * * As above, if we fail, then another thread might have * acquired a read lock, so drop the turnstile lock and * restart. */ x = RW_UNLOCKED; if (v & RW_LOCK_WRITE_WAITERS) { queue = TS_EXCLUSIVE_QUEUE; x |= (v & RW_LOCK_READ_WAITERS); } else queue = TS_SHARED_QUEUE; if (!atomic_cmpset_rel_ptr(&rw->rw_lock, RW_READERS_LOCK(1) | v, x)) { turnstile_chain_unlock(&rw->lock_object); continue; } if (LOCK_LOG_TEST(&rw->lock_object, 0)) CTR2(KTR_LOCK, "%s: %p last succeeded with waiters", __func__, rw); /* * Ok. The lock is released and all that's left is to * wake up the waiters. Note that the lock might not be * free anymore, but in that case the writers will just * block again if they run before the new lock holder(s) * release the lock. */ ts = turnstile_lookup(&rw->lock_object); MPASS(ts != NULL); turnstile_broadcast(ts, queue); turnstile_unpend(ts, TS_SHARED_LOCK); turnstile_chain_unlock(&rw->lock_object); break; } LOCKSTAT_PROFILE_RELEASE_LOCK(LS_RW_RUNLOCK_RELEASE, rw); } /* * This function is called when we are unable to obtain a write lock on the * first try. This means that at least one other thread holds either a * read or write lock. */ void _rw_wlock_hard(struct rwlock *rw, uintptr_t tid, const char *file, int line) { struct turnstile *ts; #ifdef ADAPTIVE_RWLOCKS volatile struct thread *owner; int spintries = 0; int i; #endif uintptr_t v, x; #ifdef LOCK_PROFILING uint64_t waittime = 0; int contested = 0; #endif #ifdef KDTRACE_HOOKS uint64_t spin_cnt = 0; uint64_t sleep_cnt = 0; int64_t sleep_time = 0; #endif if (rw_wlocked(rw)) { KASSERT(rw->lock_object.lo_flags & LO_RECURSABLE, ("%s: recursing but non-recursive rw %s @ %s:%d\n", __func__, rw->lock_object.lo_name, file, line)); rw->rw_recurse++; if (LOCK_LOG_TEST(&rw->lock_object, 0)) CTR2(KTR_LOCK, "%s: %p recursing", __func__, rw); return; } if (LOCK_LOG_TEST(&rw->lock_object, 0)) CTR5(KTR_LOCK, "%s: %s contested (lock=%p) at %s:%d", __func__, rw->lock_object.lo_name, (void *)rw->rw_lock, file, line); while (!_rw_write_lock(rw, tid)) { #ifdef KDTRACE_HOOKS spin_cnt++; #endif lock_profile_obtain_lock_failed(&rw->lock_object, &contested, &waittime); #ifdef ADAPTIVE_RWLOCKS /* * If the lock is write locked and the owner is * running on another CPU, spin until the owner stops * running or the state of the lock changes. */ v = rw->rw_lock; owner = (struct thread *)RW_OWNER(v); if (!(v & RW_LOCK_READ) && TD_IS_RUNNING(owner)) { if (LOCK_LOG_TEST(&rw->lock_object, 0)) CTR3(KTR_LOCK, "%s: spinning on %p held by %p", __func__, rw, owner); while ((struct thread*)RW_OWNER(rw->rw_lock) == owner && TD_IS_RUNNING(owner)) { cpu_spinwait(); #ifdef KDTRACE_HOOKS spin_cnt++; #endif } continue; } if ((v & RW_LOCK_READ) && RW_READERS(v) && - spintries < rowner_retries) { + spintries < ROWNER_RETRIES) { if (!(v & RW_LOCK_WRITE_SPINNER)) { if (!atomic_cmpset_ptr(&rw->rw_lock, v, v | RW_LOCK_WRITE_SPINNER)) { continue; } } spintries++; - for (i = 0; i < rowner_loops; i++) { + for (i = 0; i < ROWNER_LOOPS; i++) { if ((rw->rw_lock & RW_LOCK_WRITE_SPINNER) == 0) break; cpu_spinwait(); } #ifdef KDTRACE_HOOKS - spin_cnt += rowner_loops - i; + spin_cnt += ROWNER_LOOPS - i; #endif - if (i != rowner_loops) + if (i != ROWNER_LOOPS) continue; } #endif ts = turnstile_trywait(&rw->lock_object); v = rw->rw_lock; #ifdef ADAPTIVE_RWLOCKS /* * The current lock owner might have started executing * on another CPU (or the lock could have changed * owners) while we were waiting on the turnstile * chain lock. If so, drop the turnstile lock and try * again. */ if (!(v & RW_LOCK_READ)) { owner = (struct thread *)RW_OWNER(v); if (TD_IS_RUNNING(owner)) { turnstile_cancel(ts); continue; } } #endif /* * Check for the waiters flags about this rwlock. * If the lock was released, without maintain any pending * waiters queue, simply try to acquire it. * If a pending waiters queue is present, claim the lock * ownership and maintain the pending queue. */ x = v & (RW_LOCK_WAITERS | RW_LOCK_WRITE_SPINNER); if ((v & ~x) == RW_UNLOCKED) { x &= ~RW_LOCK_WRITE_SPINNER; if (atomic_cmpset_acq_ptr(&rw->rw_lock, v, tid | x)) { if (x) turnstile_claim(ts); else turnstile_cancel(ts); break; } turnstile_cancel(ts); continue; } /* * If the RW_LOCK_WRITE_WAITERS flag isn't set, then try to * set it. If we fail to set it, then loop back and try * again. */ if (!(v & RW_LOCK_WRITE_WAITERS)) { if (!atomic_cmpset_ptr(&rw->rw_lock, v, v | RW_LOCK_WRITE_WAITERS)) { turnstile_cancel(ts); continue; } if (LOCK_LOG_TEST(&rw->lock_object, 0)) CTR2(KTR_LOCK, "%s: %p set write waiters flag", __func__, rw); } /* * We were unable to acquire the lock and the write waiters * flag is set, so we must block on the turnstile. */ if (LOCK_LOG_TEST(&rw->lock_object, 0)) CTR2(KTR_LOCK, "%s: %p blocking on turnstile", __func__, rw); #ifdef KDTRACE_HOOKS sleep_time -= lockstat_nsecs(); #endif turnstile_wait(ts, rw_owner(rw), TS_EXCLUSIVE_QUEUE); #ifdef KDTRACE_HOOKS sleep_time += lockstat_nsecs(); sleep_cnt++; #endif if (LOCK_LOG_TEST(&rw->lock_object, 0)) CTR2(KTR_LOCK, "%s: %p resuming from turnstile", __func__, rw); #ifdef ADAPTIVE_RWLOCKS spintries = 0; #endif } LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_RW_WLOCK_ACQUIRE, rw, contested, waittime, file, line); #ifdef KDTRACE_HOOKS if (sleep_time) LOCKSTAT_RECORD1(LS_RW_WLOCK_BLOCK, rw, sleep_time); /* * Record only the loops spinning and not sleeping. */ if (spin_cnt > sleep_cnt) LOCKSTAT_RECORD1(LS_RW_WLOCK_SPIN, rw, (spin_cnt - sleep_cnt)); #endif } /* * This function is called if the first try at releasing a write lock failed. * This means that one of the 2 waiter bits must be set indicating that at * least one thread is waiting on this lock. */ void _rw_wunlock_hard(struct rwlock *rw, uintptr_t tid, const char *file, int line) { struct turnstile *ts; uintptr_t v; int queue; if (rw_wlocked(rw) && rw_recursed(rw)) { rw->rw_recurse--; if (LOCK_LOG_TEST(&rw->lock_object, 0)) CTR2(KTR_LOCK, "%s: %p unrecursing", __func__, rw); return; } KASSERT(rw->rw_lock & (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS), ("%s: neither of the waiter flags are set", __func__)); if (LOCK_LOG_TEST(&rw->lock_object, 0)) CTR2(KTR_LOCK, "%s: %p contested", __func__, rw); turnstile_chain_lock(&rw->lock_object); ts = turnstile_lookup(&rw->lock_object); MPASS(ts != NULL); /* * Use the same algo as sx locks for now. Prefer waking up shared * waiters if we have any over writers. This is probably not ideal. * * 'v' is the value we are going to write back to rw_lock. If we * have waiters on both queues, we need to preserve the state of * the waiter flag for the queue we don't wake up. For now this is * hardcoded for the algorithm mentioned above. * * In the case of both readers and writers waiting we wakeup the * readers but leave the RW_LOCK_WRITE_WAITERS flag set. If a * new writer comes in before a reader it will claim the lock up * above. There is probably a potential priority inversion in * there that could be worked around either by waking both queues * of waiters or doing some complicated lock handoff gymnastics. */ v = RW_UNLOCKED; if (rw->rw_lock & RW_LOCK_WRITE_WAITERS) { queue = TS_EXCLUSIVE_QUEUE; v |= (rw->rw_lock & RW_LOCK_READ_WAITERS); } else queue = TS_SHARED_QUEUE; /* Wake up all waiters for the specific queue. */ if (LOCK_LOG_TEST(&rw->lock_object, 0)) CTR3(KTR_LOCK, "%s: %p waking up %s waiters", __func__, rw, queue == TS_SHARED_QUEUE ? "read" : "write"); turnstile_broadcast(ts, queue); atomic_store_rel_ptr(&rw->rw_lock, v); turnstile_unpend(ts, TS_EXCLUSIVE_LOCK); turnstile_chain_unlock(&rw->lock_object); } /* * Attempt to do a non-blocking upgrade from a read lock to a write * lock. This will only succeed if this thread holds a single read * lock. Returns true if the upgrade succeeded and false otherwise. */ int _rw_try_upgrade(struct rwlock *rw, const char *file, int line) { uintptr_t v, x, tid; struct turnstile *ts; int success; KASSERT(rw->rw_lock != RW_DESTROYED, ("rw_try_upgrade() of destroyed rwlock @ %s:%d", file, line)); _rw_assert(rw, RA_RLOCKED, file, line); /* * Attempt to switch from one reader to a writer. If there * are any write waiters, then we will have to lock the * turnstile first to prevent races with another writer * calling turnstile_wait() before we have claimed this * turnstile. So, do the simple case of no waiters first. */ tid = (uintptr_t)curthread; success = 0; for (;;) { v = rw->rw_lock; if (RW_READERS(v) > 1) break; if (!(v & RW_LOCK_WAITERS)) { success = atomic_cmpset_ptr(&rw->rw_lock, v, tid); if (!success) continue; break; } /* * Ok, we think we have waiters, so lock the turnstile. */ ts = turnstile_trywait(&rw->lock_object); v = rw->rw_lock; if (RW_READERS(v) > 1) { turnstile_cancel(ts); break; } /* * Try to switch from one reader to a writer again. This time * we honor the current state of the waiters flags. * If we obtain the lock with the flags set, then claim * ownership of the turnstile. */ x = rw->rw_lock & RW_LOCK_WAITERS; success = atomic_cmpset_ptr(&rw->rw_lock, v, tid | x); if (success) { if (x) turnstile_claim(ts); else turnstile_cancel(ts); break; } turnstile_cancel(ts); } LOCK_LOG_TRY("WUPGRADE", &rw->lock_object, 0, success, file, line); if (success) { curthread->td_rw_rlocks--; WITNESS_UPGRADE(&rw->lock_object, LOP_EXCLUSIVE | LOP_TRYLOCK, file, line); LOCKSTAT_RECORD0(LS_RW_TRYUPGRADE_UPGRADE, rw); } return (success); } /* * Downgrade a write lock into a single read lock. */ void _rw_downgrade(struct rwlock *rw, const char *file, int line) { struct turnstile *ts; uintptr_t tid, v; int rwait, wwait; KASSERT(rw->rw_lock != RW_DESTROYED, ("rw_downgrade() of destroyed rwlock @ %s:%d", file, line)); _rw_assert(rw, RA_WLOCKED | RA_NOTRECURSED, file, line); #ifndef INVARIANTS if (rw_recursed(rw)) panic("downgrade of a recursed lock"); #endif WITNESS_DOWNGRADE(&rw->lock_object, 0, file, line); /* * Convert from a writer to a single reader. First we handle * the easy case with no waiters. If there are any waiters, we * lock the turnstile and "disown" the lock. */ tid = (uintptr_t)curthread; if (atomic_cmpset_rel_ptr(&rw->rw_lock, tid, RW_READERS_LOCK(1))) goto out; /* * Ok, we think we have waiters, so lock the turnstile so we can * read the waiter flags without any races. */ turnstile_chain_lock(&rw->lock_object); v = rw->rw_lock & RW_LOCK_WAITERS; rwait = v & RW_LOCK_READ_WAITERS; wwait = v & RW_LOCK_WRITE_WAITERS; MPASS(rwait | wwait); /* * Downgrade from a write lock while preserving waiters flag * and give up ownership of the turnstile. */ ts = turnstile_lookup(&rw->lock_object); MPASS(ts != NULL); if (!wwait) v &= ~RW_LOCK_READ_WAITERS; atomic_store_rel_ptr(&rw->rw_lock, RW_READERS_LOCK(1) | v); /* * Wake other readers if there are no writers pending. Otherwise they * won't be able to acquire the lock anyway. */ if (rwait && !wwait) { turnstile_broadcast(ts, TS_SHARED_QUEUE); turnstile_unpend(ts, TS_EXCLUSIVE_LOCK); } else turnstile_disown(ts); turnstile_chain_unlock(&rw->lock_object); out: curthread->td_rw_rlocks++; LOCK_LOG_LOCK("WDOWNGRADE", &rw->lock_object, 0, 0, file, line); LOCKSTAT_RECORD0(LS_RW_DOWNGRADE_DOWNGRADE, rw); } #ifdef INVARIANT_SUPPORT #ifndef INVARIANTS #undef _rw_assert #endif /* * In the non-WITNESS case, rw_assert() can only detect that at least * *some* thread owns an rlock, but it cannot guarantee that *this* * thread owns an rlock. */ void _rw_assert(struct rwlock *rw, int what, const char *file, int line) { if (panicstr != NULL) return; switch (what) { case RA_LOCKED: case RA_LOCKED | RA_RECURSED: case RA_LOCKED | RA_NOTRECURSED: case RA_RLOCKED: #ifdef WITNESS witness_assert(&rw->lock_object, what, file, line); #else /* * If some other thread has a write lock or we have one * and are asserting a read lock, fail. Also, if no one * has a lock at all, fail. */ if (rw->rw_lock == RW_UNLOCKED || (!(rw->rw_lock & RW_LOCK_READ) && (what == RA_RLOCKED || rw_wowner(rw) != curthread))) panic("Lock %s not %slocked @ %s:%d\n", rw->lock_object.lo_name, (what == RA_RLOCKED) ? "read " : "", file, line); if (!(rw->rw_lock & RW_LOCK_READ)) { if (rw_recursed(rw)) { if (what & RA_NOTRECURSED) panic("Lock %s recursed @ %s:%d\n", rw->lock_object.lo_name, file, line); } else if (what & RA_RECURSED) panic("Lock %s not recursed @ %s:%d\n", rw->lock_object.lo_name, file, line); } #endif break; case RA_WLOCKED: case RA_WLOCKED | RA_RECURSED: case RA_WLOCKED | RA_NOTRECURSED: if (rw_wowner(rw) != curthread) panic("Lock %s not exclusively locked @ %s:%d\n", rw->lock_object.lo_name, file, line); if (rw_recursed(rw)) { if (what & RA_NOTRECURSED) panic("Lock %s recursed @ %s:%d\n", rw->lock_object.lo_name, file, line); } else if (what & RA_RECURSED) panic("Lock %s not recursed @ %s:%d\n", rw->lock_object.lo_name, file, line); break; case RA_UNLOCKED: #ifdef WITNESS witness_assert(&rw->lock_object, what, file, line); #else /* * If we hold a write lock fail. We can't reliably check * to see if we hold a read lock or not. */ if (rw_wowner(rw) == curthread) panic("Lock %s exclusively locked @ %s:%d\n", rw->lock_object.lo_name, file, line); #endif break; default: panic("Unknown rw lock assertion: %d @ %s:%d", what, file, line); } } #endif /* INVARIANT_SUPPORT */ #ifdef DDB void db_show_rwlock(struct lock_object *lock) { struct rwlock *rw; struct thread *td; rw = (struct rwlock *)lock; db_printf(" state: "); if (rw->rw_lock == RW_UNLOCKED) db_printf("UNLOCKED\n"); else if (rw->rw_lock == RW_DESTROYED) { db_printf("DESTROYED\n"); return; } else if (rw->rw_lock & RW_LOCK_READ) db_printf("RLOCK: %ju locks\n", (uintmax_t)(RW_READERS(rw->rw_lock))); else { td = rw_wowner(rw); db_printf("WLOCK: %p (tid %d, pid %d, \"%s\")\n", td, td->td_tid, td->td_proc->p_pid, td->td_name); if (rw_recursed(rw)) db_printf(" recursed: %u\n", rw->rw_recurse); } db_printf(" waiters: "); switch (rw->rw_lock & (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS)) { case RW_LOCK_READ_WAITERS: db_printf("readers\n"); break; case RW_LOCK_WRITE_WAITERS: db_printf("writers\n"); break; case RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS: db_printf("readers and writers\n"); break; default: db_printf("none\n"); break; } } #endif Index: stable/9/sys/kern/kern_sx.c =================================================================== --- stable/9/sys/kern/kern_sx.c (revision 226254) +++ stable/9/sys/kern/kern_sx.c (revision 226255) @@ -1,1161 +1,1158 @@ /*- * Copyright (c) 2007 Attilio Rao * Copyright (c) 2001 Jason Evans * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice(s), this list of conditions and the following disclaimer as * the first lines of this file unmodified other than the possible * addition of one or more copyright notices. * 2. Redistributions in binary form must reproduce the above copyright * notice(s), this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH * DAMAGE. */ /* * Shared/exclusive locks. This implementation attempts to ensure * deterministic lock granting behavior, so that slocks and xlocks are * interleaved. * * Priority propagation will not generally raise the priority of lock holders, * so should not be relied upon in combination with sx locks. */ #include "opt_ddb.h" #include "opt_kdtrace.h" #include "opt_no_adaptive_sx.h" #include __FBSDID("$FreeBSD$"); #include #include #include #include #include #include #include #include #include #if defined(SMP) && !defined(NO_ADAPTIVE_SX) #include #endif #ifdef DDB #include #endif #if defined(SMP) && !defined(NO_ADAPTIVE_SX) #define ADAPTIVE_SX #endif CTASSERT((SX_NOADAPTIVE & LO_CLASSFLAGS) == SX_NOADAPTIVE); /* Handy macros for sleep queues. */ #define SQ_EXCLUSIVE_QUEUE 0 #define SQ_SHARED_QUEUE 1 +#ifdef ADAPTIVE_SX +#define ASX_RETRIES 10 +#define ASX_LOOPS 10000 +#endif + /* * Variations on DROP_GIANT()/PICKUP_GIANT() for use in this file. We * drop Giant anytime we have to sleep or if we adaptively spin. */ #define GIANT_DECLARE \ int _giantcnt = 0; \ WITNESS_SAVE_DECL(Giant) \ #define GIANT_SAVE() do { \ if (mtx_owned(&Giant)) { \ WITNESS_SAVE(&Giant.lock_object, Giant); \ while (mtx_owned(&Giant)) { \ _giantcnt++; \ mtx_unlock(&Giant); \ } \ } \ } while (0) #define GIANT_RESTORE() do { \ if (_giantcnt > 0) { \ mtx_assert(&Giant, MA_NOTOWNED); \ while (_giantcnt--) \ mtx_lock(&Giant); \ WITNESS_RESTORE(&Giant.lock_object, Giant); \ } \ } while (0) /* * Returns true if an exclusive lock is recursed. It assumes * curthread currently has an exclusive lock. */ #define sx_recurse lock_object.lo_data #define sx_recursed(sx) ((sx)->sx_recurse != 0) static void assert_sx(struct lock_object *lock, int what); #ifdef DDB static void db_show_sx(struct lock_object *lock); #endif static void lock_sx(struct lock_object *lock, int how); #ifdef KDTRACE_HOOKS static int owner_sx(struct lock_object *lock, struct thread **owner); #endif static int unlock_sx(struct lock_object *lock); struct lock_class lock_class_sx = { .lc_name = "sx", .lc_flags = LC_SLEEPLOCK | LC_SLEEPABLE | LC_RECURSABLE | LC_UPGRADABLE, .lc_assert = assert_sx, #ifdef DDB .lc_ddb_show = db_show_sx, #endif .lc_lock = lock_sx, .lc_unlock = unlock_sx, #ifdef KDTRACE_HOOKS .lc_owner = owner_sx, #endif }; #ifndef INVARIANTS #define _sx_assert(sx, what, file, line) #endif -#ifdef ADAPTIVE_SX -static u_int asx_retries = 10; -static u_int asx_loops = 10000; -SYSCTL_NODE(_debug, OID_AUTO, sx, CTLFLAG_RD, NULL, "sxlock debugging"); -SYSCTL_UINT(_debug_sx, OID_AUTO, retries, CTLFLAG_RW, &asx_retries, 0, ""); -SYSCTL_UINT(_debug_sx, OID_AUTO, loops, CTLFLAG_RW, &asx_loops, 0, ""); -#endif - void assert_sx(struct lock_object *lock, int what) { sx_assert((struct sx *)lock, what); } void lock_sx(struct lock_object *lock, int how) { struct sx *sx; sx = (struct sx *)lock; if (how) sx_xlock(sx); else sx_slock(sx); } int unlock_sx(struct lock_object *lock) { struct sx *sx; sx = (struct sx *)lock; sx_assert(sx, SA_LOCKED | SA_NOTRECURSED); if (sx_xlocked(sx)) { sx_xunlock(sx); return (1); } else { sx_sunlock(sx); return (0); } } #ifdef KDTRACE_HOOKS int owner_sx(struct lock_object *lock, struct thread **owner) { struct sx *sx = (struct sx *)lock; uintptr_t x = sx->sx_lock; *owner = (struct thread *)SX_OWNER(x); return ((x & SX_LOCK_SHARED) != 0 ? (SX_SHARERS(x) != 0) : (*owner != NULL)); } #endif void sx_sysinit(void *arg) { struct sx_args *sargs = arg; sx_init_flags(sargs->sa_sx, sargs->sa_desc, sargs->sa_flags); } void sx_init_flags(struct sx *sx, const char *description, int opts) { int flags; MPASS((opts & ~(SX_QUIET | SX_RECURSE | SX_NOWITNESS | SX_DUPOK | SX_NOPROFILE | SX_NOADAPTIVE)) == 0); ASSERT_ATOMIC_LOAD_PTR(sx->sx_lock, ("%s: sx_lock not aligned for %s: %p", __func__, description, &sx->sx_lock)); flags = LO_SLEEPABLE | LO_UPGRADABLE; if (opts & SX_DUPOK) flags |= LO_DUPOK; if (opts & SX_NOPROFILE) flags |= LO_NOPROFILE; if (!(opts & SX_NOWITNESS)) flags |= LO_WITNESS; if (opts & SX_RECURSE) flags |= LO_RECURSABLE; if (opts & SX_QUIET) flags |= LO_QUIET; flags |= opts & SX_NOADAPTIVE; sx->sx_lock = SX_LOCK_UNLOCKED; sx->sx_recurse = 0; lock_init(&sx->lock_object, &lock_class_sx, description, NULL, flags); } void sx_destroy(struct sx *sx) { KASSERT(sx->sx_lock == SX_LOCK_UNLOCKED, ("sx lock still held")); KASSERT(sx->sx_recurse == 0, ("sx lock still recursed")); sx->sx_lock = SX_LOCK_DESTROYED; lock_destroy(&sx->lock_object); } int _sx_slock(struct sx *sx, int opts, const char *file, int line) { int error = 0; MPASS(curthread != NULL); KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, ("sx_slock() of destroyed sx @ %s:%d", file, line)); WITNESS_CHECKORDER(&sx->lock_object, LOP_NEWORDER, file, line, NULL); error = __sx_slock(sx, opts, file, line); if (!error) { LOCK_LOG_LOCK("SLOCK", &sx->lock_object, 0, 0, file, line); WITNESS_LOCK(&sx->lock_object, 0, file, line); curthread->td_locks++; } return (error); } int _sx_try_slock(struct sx *sx, const char *file, int line) { uintptr_t x; for (;;) { x = sx->sx_lock; KASSERT(x != SX_LOCK_DESTROYED, ("sx_try_slock() of destroyed sx @ %s:%d", file, line)); if (!(x & SX_LOCK_SHARED)) break; if (atomic_cmpset_acq_ptr(&sx->sx_lock, x, x + SX_ONE_SHARER)) { LOCK_LOG_TRY("SLOCK", &sx->lock_object, 0, 1, file, line); WITNESS_LOCK(&sx->lock_object, LOP_TRYLOCK, file, line); curthread->td_locks++; return (1); } } LOCK_LOG_TRY("SLOCK", &sx->lock_object, 0, 0, file, line); return (0); } int _sx_xlock(struct sx *sx, int opts, const char *file, int line) { int error = 0; MPASS(curthread != NULL); KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, ("sx_xlock() of destroyed sx @ %s:%d", file, line)); WITNESS_CHECKORDER(&sx->lock_object, LOP_NEWORDER | LOP_EXCLUSIVE, file, line, NULL); error = __sx_xlock(sx, curthread, opts, file, line); if (!error) { LOCK_LOG_LOCK("XLOCK", &sx->lock_object, 0, sx->sx_recurse, file, line); WITNESS_LOCK(&sx->lock_object, LOP_EXCLUSIVE, file, line); curthread->td_locks++; } return (error); } int _sx_try_xlock(struct sx *sx, const char *file, int line) { int rval; MPASS(curthread != NULL); KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, ("sx_try_xlock() of destroyed sx @ %s:%d", file, line)); if (sx_xlocked(sx) && (sx->lock_object.lo_flags & LO_RECURSABLE) != 0) { sx->sx_recurse++; atomic_set_ptr(&sx->sx_lock, SX_LOCK_RECURSED); rval = 1; } else rval = atomic_cmpset_acq_ptr(&sx->sx_lock, SX_LOCK_UNLOCKED, (uintptr_t)curthread); LOCK_LOG_TRY("XLOCK", &sx->lock_object, 0, rval, file, line); if (rval) { WITNESS_LOCK(&sx->lock_object, LOP_EXCLUSIVE | LOP_TRYLOCK, file, line); curthread->td_locks++; } return (rval); } void _sx_sunlock(struct sx *sx, const char *file, int line) { MPASS(curthread != NULL); KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, ("sx_sunlock() of destroyed sx @ %s:%d", file, line)); _sx_assert(sx, SA_SLOCKED, file, line); curthread->td_locks--; WITNESS_UNLOCK(&sx->lock_object, 0, file, line); LOCK_LOG_LOCK("SUNLOCK", &sx->lock_object, 0, 0, file, line); __sx_sunlock(sx, file, line); LOCKSTAT_PROFILE_RELEASE_LOCK(LS_SX_SUNLOCK_RELEASE, sx); } void _sx_xunlock(struct sx *sx, const char *file, int line) { MPASS(curthread != NULL); KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, ("sx_xunlock() of destroyed sx @ %s:%d", file, line)); _sx_assert(sx, SA_XLOCKED, file, line); curthread->td_locks--; WITNESS_UNLOCK(&sx->lock_object, LOP_EXCLUSIVE, file, line); LOCK_LOG_LOCK("XUNLOCK", &sx->lock_object, 0, sx->sx_recurse, file, line); if (!sx_recursed(sx)) LOCKSTAT_PROFILE_RELEASE_LOCK(LS_SX_XUNLOCK_RELEASE, sx); __sx_xunlock(sx, curthread, file, line); } /* * Try to do a non-blocking upgrade from a shared lock to an exclusive lock. * This will only succeed if this thread holds a single shared lock. * Return 1 if if the upgrade succeed, 0 otherwise. */ int _sx_try_upgrade(struct sx *sx, const char *file, int line) { uintptr_t x; int success; KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, ("sx_try_upgrade() of destroyed sx @ %s:%d", file, line)); _sx_assert(sx, SA_SLOCKED, file, line); /* * Try to switch from one shared lock to an exclusive lock. We need * to maintain the SX_LOCK_EXCLUSIVE_WAITERS flag if set so that * we will wake up the exclusive waiters when we drop the lock. */ x = sx->sx_lock & SX_LOCK_EXCLUSIVE_WAITERS; success = atomic_cmpset_ptr(&sx->sx_lock, SX_SHARERS_LOCK(1) | x, (uintptr_t)curthread | x); LOCK_LOG_TRY("XUPGRADE", &sx->lock_object, 0, success, file, line); if (success) { WITNESS_UPGRADE(&sx->lock_object, LOP_EXCLUSIVE | LOP_TRYLOCK, file, line); LOCKSTAT_RECORD0(LS_SX_TRYUPGRADE_UPGRADE, sx); } return (success); } /* * Downgrade an unrecursed exclusive lock into a single shared lock. */ void _sx_downgrade(struct sx *sx, const char *file, int line) { uintptr_t x; int wakeup_swapper; KASSERT(sx->sx_lock != SX_LOCK_DESTROYED, ("sx_downgrade() of destroyed sx @ %s:%d", file, line)); _sx_assert(sx, SA_XLOCKED | SA_NOTRECURSED, file, line); #ifndef INVARIANTS if (sx_recursed(sx)) panic("downgrade of a recursed lock"); #endif WITNESS_DOWNGRADE(&sx->lock_object, 0, file, line); /* * Try to switch from an exclusive lock with no shared waiters * to one sharer with no shared waiters. If there are * exclusive waiters, we don't need to lock the sleep queue so * long as we preserve the flag. We do one quick try and if * that fails we grab the sleepq lock to keep the flags from * changing and do it the slow way. * * We have to lock the sleep queue if there are shared waiters * so we can wake them up. */ x = sx->sx_lock; if (!(x & SX_LOCK_SHARED_WAITERS) && atomic_cmpset_rel_ptr(&sx->sx_lock, x, SX_SHARERS_LOCK(1) | (x & SX_LOCK_EXCLUSIVE_WAITERS))) { LOCK_LOG_LOCK("XDOWNGRADE", &sx->lock_object, 0, 0, file, line); return; } /* * Lock the sleep queue so we can read the waiters bits * without any races and wakeup any shared waiters. */ sleepq_lock(&sx->lock_object); /* * Preserve SX_LOCK_EXCLUSIVE_WAITERS while downgraded to a single * shared lock. If there are any shared waiters, wake them up. */ wakeup_swapper = 0; x = sx->sx_lock; atomic_store_rel_ptr(&sx->sx_lock, SX_SHARERS_LOCK(1) | (x & SX_LOCK_EXCLUSIVE_WAITERS)); if (x & SX_LOCK_SHARED_WAITERS) wakeup_swapper = sleepq_broadcast(&sx->lock_object, SLEEPQ_SX, 0, SQ_SHARED_QUEUE); sleepq_release(&sx->lock_object); LOCK_LOG_LOCK("XDOWNGRADE", &sx->lock_object, 0, 0, file, line); LOCKSTAT_RECORD0(LS_SX_DOWNGRADE_DOWNGRADE, sx); if (wakeup_swapper) kick_proc0(); } /* * This function represents the so-called 'hard case' for sx_xlock * operation. All 'easy case' failures are redirected to this. Note * that ideally this would be a static function, but it needs to be * accessible from at least sx.h. */ int _sx_xlock_hard(struct sx *sx, uintptr_t tid, int opts, const char *file, int line) { GIANT_DECLARE; #ifdef ADAPTIVE_SX volatile struct thread *owner; u_int i, spintries = 0; #endif uintptr_t x; #ifdef LOCK_PROFILING uint64_t waittime = 0; int contested = 0; #endif int error = 0; #ifdef KDTRACE_HOOKS uint64_t spin_cnt = 0; uint64_t sleep_cnt = 0; int64_t sleep_time = 0; #endif /* If we already hold an exclusive lock, then recurse. */ if (sx_xlocked(sx)) { KASSERT((sx->lock_object.lo_flags & LO_RECURSABLE) != 0, ("_sx_xlock_hard: recursed on non-recursive sx %s @ %s:%d\n", sx->lock_object.lo_name, file, line)); sx->sx_recurse++; atomic_set_ptr(&sx->sx_lock, SX_LOCK_RECURSED); if (LOCK_LOG_TEST(&sx->lock_object, 0)) CTR2(KTR_LOCK, "%s: %p recursing", __func__, sx); return (0); } if (LOCK_LOG_TEST(&sx->lock_object, 0)) CTR5(KTR_LOCK, "%s: %s contested (lock=%p) at %s:%d", __func__, sx->lock_object.lo_name, (void *)sx->sx_lock, file, line); while (!atomic_cmpset_acq_ptr(&sx->sx_lock, SX_LOCK_UNLOCKED, tid)) { #ifdef KDTRACE_HOOKS spin_cnt++; #endif lock_profile_obtain_lock_failed(&sx->lock_object, &contested, &waittime); #ifdef ADAPTIVE_SX /* * If the lock is write locked and the owner is * running on another CPU, spin until the owner stops * running or the state of the lock changes. */ x = sx->sx_lock; if ((sx->lock_object.lo_flags & SX_NOADAPTIVE) == 0) { if ((x & SX_LOCK_SHARED) == 0) { x = SX_OWNER(x); owner = (struct thread *)x; if (TD_IS_RUNNING(owner)) { if (LOCK_LOG_TEST(&sx->lock_object, 0)) CTR3(KTR_LOCK, "%s: spinning on %p held by %p", __func__, sx, owner); GIANT_SAVE(); while (SX_OWNER(sx->sx_lock) == x && TD_IS_RUNNING(owner)) { cpu_spinwait(); #ifdef KDTRACE_HOOKS spin_cnt++; #endif } continue; } - } else if (SX_SHARERS(x) && spintries < asx_retries) { + } else if (SX_SHARERS(x) && spintries < ASX_RETRIES) { GIANT_SAVE(); spintries++; - for (i = 0; i < asx_loops; i++) { + for (i = 0; i < ASX_LOOPS; i++) { if (LOCK_LOG_TEST(&sx->lock_object, 0)) CTR4(KTR_LOCK, "%s: shared spinning on %p with %u and %u", __func__, sx, spintries, i); x = sx->sx_lock; if ((x & SX_LOCK_SHARED) == 0 || SX_SHARERS(x) == 0) break; cpu_spinwait(); #ifdef KDTRACE_HOOKS spin_cnt++; #endif } - if (i != asx_loops) + if (i != ASX_LOOPS) continue; } } #endif sleepq_lock(&sx->lock_object); x = sx->sx_lock; /* * If the lock was released while spinning on the * sleep queue chain lock, try again. */ if (x == SX_LOCK_UNLOCKED) { sleepq_release(&sx->lock_object); continue; } #ifdef ADAPTIVE_SX /* * The current lock owner might have started executing * on another CPU (or the lock could have changed * owners) while we were waiting on the sleep queue * chain lock. If so, drop the sleep queue lock and try * again. */ if (!(x & SX_LOCK_SHARED) && (sx->lock_object.lo_flags & SX_NOADAPTIVE) == 0) { owner = (struct thread *)SX_OWNER(x); if (TD_IS_RUNNING(owner)) { sleepq_release(&sx->lock_object); continue; } } #endif /* * If an exclusive lock was released with both shared * and exclusive waiters and a shared waiter hasn't * woken up and acquired the lock yet, sx_lock will be * set to SX_LOCK_UNLOCKED | SX_LOCK_EXCLUSIVE_WAITERS. * If we see that value, try to acquire it once. Note * that we have to preserve SX_LOCK_EXCLUSIVE_WAITERS * as there are other exclusive waiters still. If we * fail, restart the loop. */ if (x == (SX_LOCK_UNLOCKED | SX_LOCK_EXCLUSIVE_WAITERS)) { if (atomic_cmpset_acq_ptr(&sx->sx_lock, SX_LOCK_UNLOCKED | SX_LOCK_EXCLUSIVE_WAITERS, tid | SX_LOCK_EXCLUSIVE_WAITERS)) { sleepq_release(&sx->lock_object); CTR2(KTR_LOCK, "%s: %p claimed by new writer", __func__, sx); break; } sleepq_release(&sx->lock_object); continue; } /* * Try to set the SX_LOCK_EXCLUSIVE_WAITERS. If we fail, * than loop back and retry. */ if (!(x & SX_LOCK_EXCLUSIVE_WAITERS)) { if (!atomic_cmpset_ptr(&sx->sx_lock, x, x | SX_LOCK_EXCLUSIVE_WAITERS)) { sleepq_release(&sx->lock_object); continue; } if (LOCK_LOG_TEST(&sx->lock_object, 0)) CTR2(KTR_LOCK, "%s: %p set excl waiters flag", __func__, sx); } /* * Since we have been unable to acquire the exclusive * lock and the exclusive waiters flag is set, we have * to sleep. */ if (LOCK_LOG_TEST(&sx->lock_object, 0)) CTR2(KTR_LOCK, "%s: %p blocking on sleep queue", __func__, sx); #ifdef KDTRACE_HOOKS sleep_time -= lockstat_nsecs(); #endif GIANT_SAVE(); sleepq_add(&sx->lock_object, NULL, sx->lock_object.lo_name, SLEEPQ_SX | ((opts & SX_INTERRUPTIBLE) ? SLEEPQ_INTERRUPTIBLE : 0), SQ_EXCLUSIVE_QUEUE); if (!(opts & SX_INTERRUPTIBLE)) sleepq_wait(&sx->lock_object, 0); else error = sleepq_wait_sig(&sx->lock_object, 0); #ifdef KDTRACE_HOOKS sleep_time += lockstat_nsecs(); sleep_cnt++; #endif if (error) { if (LOCK_LOG_TEST(&sx->lock_object, 0)) CTR2(KTR_LOCK, "%s: interruptible sleep by %p suspended by signal", __func__, sx); break; } if (LOCK_LOG_TEST(&sx->lock_object, 0)) CTR2(KTR_LOCK, "%s: %p resuming from sleep queue", __func__, sx); } GIANT_RESTORE(); if (!error) LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_SX_XLOCK_ACQUIRE, sx, contested, waittime, file, line); #ifdef KDTRACE_HOOKS if (sleep_time) LOCKSTAT_RECORD1(LS_SX_XLOCK_BLOCK, sx, sleep_time); if (spin_cnt > sleep_cnt) LOCKSTAT_RECORD1(LS_SX_XLOCK_SPIN, sx, (spin_cnt - sleep_cnt)); #endif return (error); } /* * This function represents the so-called 'hard case' for sx_xunlock * operation. All 'easy case' failures are redirected to this. Note * that ideally this would be a static function, but it needs to be * accessible from at least sx.h. */ void _sx_xunlock_hard(struct sx *sx, uintptr_t tid, const char *file, int line) { uintptr_t x; int queue, wakeup_swapper; MPASS(!(sx->sx_lock & SX_LOCK_SHARED)); /* If the lock is recursed, then unrecurse one level. */ if (sx_xlocked(sx) && sx_recursed(sx)) { if ((--sx->sx_recurse) == 0) atomic_clear_ptr(&sx->sx_lock, SX_LOCK_RECURSED); if (LOCK_LOG_TEST(&sx->lock_object, 0)) CTR2(KTR_LOCK, "%s: %p unrecursing", __func__, sx); return; } MPASS(sx->sx_lock & (SX_LOCK_SHARED_WAITERS | SX_LOCK_EXCLUSIVE_WAITERS)); if (LOCK_LOG_TEST(&sx->lock_object, 0)) CTR2(KTR_LOCK, "%s: %p contested", __func__, sx); sleepq_lock(&sx->lock_object); x = SX_LOCK_UNLOCKED; /* * The wake up algorithm here is quite simple and probably not * ideal. It gives precedence to shared waiters if they are * present. For this condition, we have to preserve the * state of the exclusive waiters flag. * If interruptible sleeps left the shared queue empty avoid a * starvation for the threads sleeping on the exclusive queue by giving * them precedence and cleaning up the shared waiters bit anyway. */ if ((sx->sx_lock & SX_LOCK_SHARED_WAITERS) != 0 && sleepq_sleepcnt(&sx->lock_object, SQ_SHARED_QUEUE) != 0) { queue = SQ_SHARED_QUEUE; x |= (sx->sx_lock & SX_LOCK_EXCLUSIVE_WAITERS); } else queue = SQ_EXCLUSIVE_QUEUE; /* Wake up all the waiters for the specific queue. */ if (LOCK_LOG_TEST(&sx->lock_object, 0)) CTR3(KTR_LOCK, "%s: %p waking up all threads on %s queue", __func__, sx, queue == SQ_SHARED_QUEUE ? "shared" : "exclusive"); atomic_store_rel_ptr(&sx->sx_lock, x); wakeup_swapper = sleepq_broadcast(&sx->lock_object, SLEEPQ_SX, 0, queue); sleepq_release(&sx->lock_object); if (wakeup_swapper) kick_proc0(); } /* * This function represents the so-called 'hard case' for sx_slock * operation. All 'easy case' failures are redirected to this. Note * that ideally this would be a static function, but it needs to be * accessible from at least sx.h. */ int _sx_slock_hard(struct sx *sx, int opts, const char *file, int line) { GIANT_DECLARE; #ifdef ADAPTIVE_SX volatile struct thread *owner; #endif #ifdef LOCK_PROFILING uint64_t waittime = 0; int contested = 0; #endif uintptr_t x; int error = 0; #ifdef KDTRACE_HOOKS uint64_t spin_cnt = 0; uint64_t sleep_cnt = 0; int64_t sleep_time = 0; #endif /* * As with rwlocks, we don't make any attempt to try to block * shared locks once there is an exclusive waiter. */ for (;;) { #ifdef KDTRACE_HOOKS spin_cnt++; #endif x = sx->sx_lock; /* * If no other thread has an exclusive lock then try to bump up * the count of sharers. Since we have to preserve the state * of SX_LOCK_EXCLUSIVE_WAITERS, if we fail to acquire the * shared lock loop back and retry. */ if (x & SX_LOCK_SHARED) { MPASS(!(x & SX_LOCK_SHARED_WAITERS)); if (atomic_cmpset_acq_ptr(&sx->sx_lock, x, x + SX_ONE_SHARER)) { if (LOCK_LOG_TEST(&sx->lock_object, 0)) CTR4(KTR_LOCK, "%s: %p succeed %p -> %p", __func__, sx, (void *)x, (void *)(x + SX_ONE_SHARER)); break; } continue; } lock_profile_obtain_lock_failed(&sx->lock_object, &contested, &waittime); #ifdef ADAPTIVE_SX /* * If the owner is running on another CPU, spin until * the owner stops running or the state of the lock * changes. */ if ((sx->lock_object.lo_flags & SX_NOADAPTIVE) == 0) { x = SX_OWNER(x); owner = (struct thread *)x; if (TD_IS_RUNNING(owner)) { if (LOCK_LOG_TEST(&sx->lock_object, 0)) CTR3(KTR_LOCK, "%s: spinning on %p held by %p", __func__, sx, owner); GIANT_SAVE(); while (SX_OWNER(sx->sx_lock) == x && TD_IS_RUNNING(owner)) { #ifdef KDTRACE_HOOKS spin_cnt++; #endif cpu_spinwait(); } continue; } } #endif /* * Some other thread already has an exclusive lock, so * start the process of blocking. */ sleepq_lock(&sx->lock_object); x = sx->sx_lock; /* * The lock could have been released while we spun. * In this case loop back and retry. */ if (x & SX_LOCK_SHARED) { sleepq_release(&sx->lock_object); continue; } #ifdef ADAPTIVE_SX /* * If the owner is running on another CPU, spin until * the owner stops running or the state of the lock * changes. */ if (!(x & SX_LOCK_SHARED) && (sx->lock_object.lo_flags & SX_NOADAPTIVE) == 0) { owner = (struct thread *)SX_OWNER(x); if (TD_IS_RUNNING(owner)) { sleepq_release(&sx->lock_object); continue; } } #endif /* * Try to set the SX_LOCK_SHARED_WAITERS flag. If we * fail to set it drop the sleep queue lock and loop * back. */ if (!(x & SX_LOCK_SHARED_WAITERS)) { if (!atomic_cmpset_ptr(&sx->sx_lock, x, x | SX_LOCK_SHARED_WAITERS)) { sleepq_release(&sx->lock_object); continue; } if (LOCK_LOG_TEST(&sx->lock_object, 0)) CTR2(KTR_LOCK, "%s: %p set shared waiters flag", __func__, sx); } /* * Since we have been unable to acquire the shared lock, * we have to sleep. */ if (LOCK_LOG_TEST(&sx->lock_object, 0)) CTR2(KTR_LOCK, "%s: %p blocking on sleep queue", __func__, sx); #ifdef KDTRACE_HOOKS sleep_time -= lockstat_nsecs(); #endif GIANT_SAVE(); sleepq_add(&sx->lock_object, NULL, sx->lock_object.lo_name, SLEEPQ_SX | ((opts & SX_INTERRUPTIBLE) ? SLEEPQ_INTERRUPTIBLE : 0), SQ_SHARED_QUEUE); if (!(opts & SX_INTERRUPTIBLE)) sleepq_wait(&sx->lock_object, 0); else error = sleepq_wait_sig(&sx->lock_object, 0); #ifdef KDTRACE_HOOKS sleep_time += lockstat_nsecs(); sleep_cnt++; #endif if (error) { if (LOCK_LOG_TEST(&sx->lock_object, 0)) CTR2(KTR_LOCK, "%s: interruptible sleep by %p suspended by signal", __func__, sx); break; } if (LOCK_LOG_TEST(&sx->lock_object, 0)) CTR2(KTR_LOCK, "%s: %p resuming from sleep queue", __func__, sx); } if (error == 0) LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(LS_SX_SLOCK_ACQUIRE, sx, contested, waittime, file, line); #ifdef KDTRACE_HOOKS if (sleep_time) LOCKSTAT_RECORD1(LS_SX_XLOCK_BLOCK, sx, sleep_time); if (spin_cnt > sleep_cnt) LOCKSTAT_RECORD1(LS_SX_XLOCK_SPIN, sx, (spin_cnt - sleep_cnt)); #endif GIANT_RESTORE(); return (error); } /* * This function represents the so-called 'hard case' for sx_sunlock * operation. All 'easy case' failures are redirected to this. Note * that ideally this would be a static function, but it needs to be * accessible from at least sx.h. */ void _sx_sunlock_hard(struct sx *sx, const char *file, int line) { uintptr_t x; int wakeup_swapper; for (;;) { x = sx->sx_lock; /* * We should never have sharers while at least one thread * holds a shared lock. */ KASSERT(!(x & SX_LOCK_SHARED_WAITERS), ("%s: waiting sharers", __func__)); /* * See if there is more than one shared lock held. If * so, just drop one and return. */ if (SX_SHARERS(x) > 1) { if (atomic_cmpset_rel_ptr(&sx->sx_lock, x, x - SX_ONE_SHARER)) { if (LOCK_LOG_TEST(&sx->lock_object, 0)) CTR4(KTR_LOCK, "%s: %p succeeded %p -> %p", __func__, sx, (void *)x, (void *)(x - SX_ONE_SHARER)); break; } continue; } /* * If there aren't any waiters for an exclusive lock, * then try to drop it quickly. */ if (!(x & SX_LOCK_EXCLUSIVE_WAITERS)) { MPASS(x == SX_SHARERS_LOCK(1)); if (atomic_cmpset_rel_ptr(&sx->sx_lock, SX_SHARERS_LOCK(1), SX_LOCK_UNLOCKED)) { if (LOCK_LOG_TEST(&sx->lock_object, 0)) CTR2(KTR_LOCK, "%s: %p last succeeded", __func__, sx); break; } continue; } /* * At this point, there should just be one sharer with * exclusive waiters. */ MPASS(x == (SX_SHARERS_LOCK(1) | SX_LOCK_EXCLUSIVE_WAITERS)); sleepq_lock(&sx->lock_object); /* * Wake up semantic here is quite simple: * Just wake up all the exclusive waiters. * Note that the state of the lock could have changed, * so if it fails loop back and retry. */ if (!atomic_cmpset_rel_ptr(&sx->sx_lock, SX_SHARERS_LOCK(1) | SX_LOCK_EXCLUSIVE_WAITERS, SX_LOCK_UNLOCKED)) { sleepq_release(&sx->lock_object); continue; } if (LOCK_LOG_TEST(&sx->lock_object, 0)) CTR2(KTR_LOCK, "%s: %p waking up all thread on" "exclusive queue", __func__, sx); wakeup_swapper = sleepq_broadcast(&sx->lock_object, SLEEPQ_SX, 0, SQ_EXCLUSIVE_QUEUE); sleepq_release(&sx->lock_object); if (wakeup_swapper) kick_proc0(); break; } } #ifdef INVARIANT_SUPPORT #ifndef INVARIANTS #undef _sx_assert #endif /* * In the non-WITNESS case, sx_assert() can only detect that at least * *some* thread owns an slock, but it cannot guarantee that *this* * thread owns an slock. */ void _sx_assert(struct sx *sx, int what, const char *file, int line) { #ifndef WITNESS int slocked = 0; #endif if (panicstr != NULL) return; switch (what) { case SA_SLOCKED: case SA_SLOCKED | SA_NOTRECURSED: case SA_SLOCKED | SA_RECURSED: #ifndef WITNESS slocked = 1; /* FALLTHROUGH */ #endif case SA_LOCKED: case SA_LOCKED | SA_NOTRECURSED: case SA_LOCKED | SA_RECURSED: #ifdef WITNESS witness_assert(&sx->lock_object, what, file, line); #else /* * If some other thread has an exclusive lock or we * have one and are asserting a shared lock, fail. * Also, if no one has a lock at all, fail. */ if (sx->sx_lock == SX_LOCK_UNLOCKED || (!(sx->sx_lock & SX_LOCK_SHARED) && (slocked || sx_xholder(sx) != curthread))) panic("Lock %s not %slocked @ %s:%d\n", sx->lock_object.lo_name, slocked ? "share " : "", file, line); if (!(sx->sx_lock & SX_LOCK_SHARED)) { if (sx_recursed(sx)) { if (what & SA_NOTRECURSED) panic("Lock %s recursed @ %s:%d\n", sx->lock_object.lo_name, file, line); } else if (what & SA_RECURSED) panic("Lock %s not recursed @ %s:%d\n", sx->lock_object.lo_name, file, line); } #endif break; case SA_XLOCKED: case SA_XLOCKED | SA_NOTRECURSED: case SA_XLOCKED | SA_RECURSED: if (sx_xholder(sx) != curthread) panic("Lock %s not exclusively locked @ %s:%d\n", sx->lock_object.lo_name, file, line); if (sx_recursed(sx)) { if (what & SA_NOTRECURSED) panic("Lock %s recursed @ %s:%d\n", sx->lock_object.lo_name, file, line); } else if (what & SA_RECURSED) panic("Lock %s not recursed @ %s:%d\n", sx->lock_object.lo_name, file, line); break; case SA_UNLOCKED: #ifdef WITNESS witness_assert(&sx->lock_object, what, file, line); #else /* * If we hold an exclusve lock fail. We can't * reliably check to see if we hold a shared lock or * not. */ if (sx_xholder(sx) == curthread) panic("Lock %s exclusively locked @ %s:%d\n", sx->lock_object.lo_name, file, line); #endif break; default: panic("Unknown sx lock assertion: %d @ %s:%d", what, file, line); } } #endif /* INVARIANT_SUPPORT */ #ifdef DDB static void db_show_sx(struct lock_object *lock) { struct thread *td; struct sx *sx; sx = (struct sx *)lock; db_printf(" state: "); if (sx->sx_lock == SX_LOCK_UNLOCKED) db_printf("UNLOCKED\n"); else if (sx->sx_lock == SX_LOCK_DESTROYED) { db_printf("DESTROYED\n"); return; } else if (sx->sx_lock & SX_LOCK_SHARED) db_printf("SLOCK: %ju\n", (uintmax_t)SX_SHARERS(sx->sx_lock)); else { td = sx_xholder(sx); db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td, td->td_tid, td->td_proc->p_pid, td->td_name); if (sx_recursed(sx)) db_printf(" recursed: %d\n", sx->sx_recurse); } db_printf(" waiters: "); switch(sx->sx_lock & (SX_LOCK_SHARED_WAITERS | SX_LOCK_EXCLUSIVE_WAITERS)) { case SX_LOCK_SHARED_WAITERS: db_printf("shared\n"); break; case SX_LOCK_EXCLUSIVE_WAITERS: db_printf("exclusive\n"); break; case SX_LOCK_SHARED_WAITERS | SX_LOCK_EXCLUSIVE_WAITERS: db_printf("exclusive and shared\n"); break; default: db_printf("none\n"); } } /* * Check to see if a thread that is blocked on a sleep queue is actually * blocked on an sx lock. If so, output some details and return true. * If the lock has an exclusive owner, return that in *ownerp. */ int sx_chain(struct thread *td, struct thread **ownerp) { struct sx *sx; /* * Check to see if this thread is blocked on an sx lock. * First, we check the lock class. If that is ok, then we * compare the lock name against the wait message. */ sx = td->td_wchan; if (LOCK_CLASS(&sx->lock_object) != &lock_class_sx || sx->lock_object.lo_name != td->td_wmesg) return (0); /* We think we have an sx lock, so output some details. */ db_printf("blocked on sx \"%s\" ", td->td_wmesg); *ownerp = sx_xholder(sx); if (sx->sx_lock & SX_LOCK_SHARED) db_printf("SLOCK (count %ju)\n", (uintmax_t)SX_SHARERS(sx->sx_lock)); else db_printf("XLOCK\n"); return (1); } #endif