diff --git a/sys/compat/linuxkpi/common/src/linux_rcu.c b/sys/compat/linuxkpi/common/src/linux_rcu.c index a39949cf5013..2179faa2c05e 100644 --- a/sys/compat/linuxkpi/common/src/linux_rcu.c +++ b/sys/compat/linuxkpi/common/src/linux_rcu.c @@ -1,428 +1,432 @@ /*- * Copyright (c) 2016 Matthew Macy (mmacy@mattmacy.io) * Copyright (c) 2017-2021 Hans Petter Selasky (hselasky@freebsd.org) * 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 unmodified, 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. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 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 __FBSDID("$FreeBSD$"); #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* * By defining CONFIG_NO_RCU_SKIP LinuxKPI RCU locks and asserts will * not be skipped during panic(). */ #ifdef CONFIG_NO_RCU_SKIP #define RCU_SKIP(void) 0 #else #define RCU_SKIP(void) unlikely(SCHEDULER_STOPPED() || kdb_active) #endif struct callback_head { union { STAILQ_ENTRY(callback_head) entry; struct llist_node node; }; rcu_callback_t func; }; struct linux_epoch_head { struct llist_head cb_head; struct task task; } __aligned(CACHE_LINE_SIZE); struct linux_epoch_record { ck_epoch_record_t epoch_record; TAILQ_HEAD(, task_struct) ts_head; int cpuid; int type; } __aligned(CACHE_LINE_SIZE); /* * Verify that "struct rcu_head" is big enough to hold "struct * callback_head". This has been done to avoid having to add special * compile flags for including ck_epoch.h to all clients of the * LinuxKPI. */ CTASSERT(sizeof(struct rcu_head) == sizeof(struct callback_head)); /* * Verify that "rcu_section[0]" has the same size as * "ck_epoch_section_t". This has been done to avoid having to add * special compile flags for including ck_epoch.h to all clients of * the LinuxKPI. */ CTASSERT(sizeof(((struct task_struct *)0)->rcu_section[0] == sizeof(ck_epoch_section_t))); /* * Verify that "epoch_record" is at beginning of "struct * linux_epoch_record": */ CTASSERT(offsetof(struct linux_epoch_record, epoch_record) == 0); CTASSERT(TS_RCU_TYPE_MAX == RCU_TYPE_MAX); static ck_epoch_t linux_epoch[RCU_TYPE_MAX]; static struct linux_epoch_head linux_epoch_head[RCU_TYPE_MAX]; DPCPU_DEFINE_STATIC(struct linux_epoch_record, linux_epoch_record[RCU_TYPE_MAX]); static void linux_rcu_cleaner_func(void *, int); static void linux_rcu_runtime_init(void *arg __unused) { struct linux_epoch_head *head; int i; int j; for (j = 0; j != RCU_TYPE_MAX; j++) { ck_epoch_init(&linux_epoch[j]); head = &linux_epoch_head[j]; TASK_INIT(&head->task, 0, linux_rcu_cleaner_func, head); init_llist_head(&head->cb_head); CPU_FOREACH(i) { struct linux_epoch_record *record; record = &DPCPU_ID_GET(i, linux_epoch_record[j]); record->cpuid = i; record->type = j; ck_epoch_register(&linux_epoch[j], &record->epoch_record, NULL); TAILQ_INIT(&record->ts_head); } } } SYSINIT(linux_rcu_runtime, SI_SUB_CPU, SI_ORDER_ANY, linux_rcu_runtime_init, NULL); static void linux_rcu_cleaner_func(void *context, int pending __unused) { struct linux_epoch_head *head = context; struct callback_head *rcu; STAILQ_HEAD(, callback_head) tmp_head; struct llist_node *node, *next; uintptr_t offset; /* move current callbacks into own queue */ STAILQ_INIT(&tmp_head); llist_for_each_safe(node, next, llist_del_all(&head->cb_head)) { rcu = container_of(node, struct callback_head, node); /* re-reverse list to restore chronological order */ STAILQ_INSERT_HEAD(&tmp_head, rcu, entry); } /* synchronize */ linux_synchronize_rcu(head - linux_epoch_head); /* dispatch all callbacks, if any */ while ((rcu = STAILQ_FIRST(&tmp_head)) != NULL) { STAILQ_REMOVE_HEAD(&tmp_head, entry); offset = (uintptr_t)rcu->func; if (offset < LINUX_KFREE_RCU_OFFSET_MAX) kfree((char *)rcu - offset); else rcu->func((struct rcu_head *)rcu); } } void linux_rcu_read_lock(unsigned type) { struct linux_epoch_record *record; struct task_struct *ts; MPASS(type < RCU_TYPE_MAX); if (RCU_SKIP()) return; ts = current; /* assert valid refcount */ MPASS(ts->rcu_recurse[type] != INT_MAX); if (++(ts->rcu_recurse[type]) != 1) return; /* * Pin thread to current CPU so that the unlock code gets the * same per-CPU epoch record: */ sched_pin(); record = &DPCPU_GET(linux_epoch_record[type]); /* * Use a critical section to prevent recursion inside * ck_epoch_begin(). Else this function supports recursion. */ critical_enter(); ck_epoch_begin(&record->epoch_record, (ck_epoch_section_t *)&ts->rcu_section[type]); TAILQ_INSERT_TAIL(&record->ts_head, ts, rcu_entry[type]); critical_exit(); } void linux_rcu_read_unlock(unsigned type) { struct linux_epoch_record *record; struct task_struct *ts; MPASS(type < RCU_TYPE_MAX); if (RCU_SKIP()) return; ts = current; /* assert valid refcount */ MPASS(ts->rcu_recurse[type] > 0); if (--(ts->rcu_recurse[type]) != 0) return; record = &DPCPU_GET(linux_epoch_record[type]); /* * Use a critical section to prevent recursion inside * ck_epoch_end(). Else this function supports recursion. */ critical_enter(); ck_epoch_end(&record->epoch_record, (ck_epoch_section_t *)&ts->rcu_section[type]); TAILQ_REMOVE(&record->ts_head, ts, rcu_entry[type]); critical_exit(); sched_unpin(); } static void linux_synchronize_rcu_cb(ck_epoch_t *epoch __unused, ck_epoch_record_t *epoch_record, void *arg __unused) { struct linux_epoch_record *record = container_of(epoch_record, struct linux_epoch_record, epoch_record); struct thread *td = curthread; struct task_struct *ts; /* check if blocked on the current CPU */ if (record->cpuid == PCPU_GET(cpuid)) { bool is_sleeping = 0; u_char prio = 0; /* * Find the lowest priority or sleeping thread which * is blocking synchronization on this CPU core. All * the threads in the queue are CPU-pinned and cannot * go anywhere while the current thread is locked. */ TAILQ_FOREACH(ts, &record->ts_head, rcu_entry[record->type]) { if (ts->task_thread->td_priority > prio) prio = ts->task_thread->td_priority; is_sleeping |= (ts->task_thread->td_inhibitors != 0); } if (is_sleeping) { thread_unlock(td); pause("W", 1); thread_lock(td); } else { /* set new thread priority */ sched_prio(td, prio); /* task switch */ mi_switch(SW_VOL | SWT_RELINQUISH); /* * It is important the thread lock is dropped * while yielding to allow other threads to * acquire the lock pointed to by * TDQ_LOCKPTR(td). Currently mi_switch() will * unlock the thread lock before * returning. Else a deadlock like situation * might happen. */ thread_lock(td); } } else { /* * To avoid spinning move execution to the other CPU * which is blocking synchronization. Set highest * thread priority so that code gets run. The thread * priority will be restored later. */ sched_prio(td, 0); sched_bind(td, record->cpuid); } } void linux_synchronize_rcu(unsigned type) { struct thread *td; int was_bound; int old_cpu; int old_pinned; u_char old_prio; MPASS(type < RCU_TYPE_MAX); if (RCU_SKIP()) return; WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "linux_synchronize_rcu() can sleep"); td = curthread; DROP_GIANT(); /* * Synchronizing RCU might change the CPU core this function * is running on. Save current values: */ thread_lock(td); old_cpu = PCPU_GET(cpuid); old_pinned = td->td_pinned; old_prio = td->td_priority; was_bound = sched_is_bound(td); sched_unbind(td); td->td_pinned = 0; sched_bind(td, old_cpu); ck_epoch_synchronize_wait(&linux_epoch[type], &linux_synchronize_rcu_cb, NULL); /* restore CPU binding, if any */ if (was_bound != 0) { sched_bind(td, old_cpu); } else { /* get thread back to initial CPU, if any */ if (old_pinned != 0) sched_bind(td, old_cpu); sched_unbind(td); } /* restore pinned after bind */ td->td_pinned = old_pinned; /* restore thread priority */ sched_prio(td, old_prio); thread_unlock(td); PICKUP_GIANT(); } void linux_rcu_barrier(unsigned type) { struct linux_epoch_head *head; MPASS(type < RCU_TYPE_MAX); - linux_synchronize_rcu(type); - + /* + * This function is not obligated to wait for a grace period. + * It only waits for RCU callbacks that have already been posted. + * If there are no RCU callbacks posted, rcu_barrier() can return + * immediately. + */ head = &linux_epoch_head[type]; /* wait for callbacks to complete */ taskqueue_drain(linux_irq_work_tq, &head->task); } void linux_call_rcu(unsigned type, struct rcu_head *context, rcu_callback_t func) { struct callback_head *rcu; struct linux_epoch_head *head; MPASS(type < RCU_TYPE_MAX); rcu = (struct callback_head *)context; head = &linux_epoch_head[type]; rcu->func = func; llist_add(&rcu->node, &head->cb_head); taskqueue_enqueue(linux_irq_work_tq, &head->task); } int init_srcu_struct(struct srcu_struct *srcu) { return (0); } void cleanup_srcu_struct(struct srcu_struct *srcu) { } int srcu_read_lock(struct srcu_struct *srcu) { linux_rcu_read_lock(RCU_TYPE_SLEEPABLE); return (0); } void srcu_read_unlock(struct srcu_struct *srcu, int key __unused) { linux_rcu_read_unlock(RCU_TYPE_SLEEPABLE); } void synchronize_srcu(struct srcu_struct *srcu) { linux_synchronize_rcu(RCU_TYPE_SLEEPABLE); } void srcu_barrier(struct srcu_struct *srcu) { linux_rcu_barrier(RCU_TYPE_SLEEPABLE); }