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diff --git a/sys/compat/linux/linux_fork.c b/sys/compat/linux/linux_fork.c
--- a/sys/compat/linux/linux_fork.c
+++ b/sys/compat/linux/linux_fork.c
@@ -45,6 +45,7 @@
#include <sys/sched.h>
#include <sys/syscallsubr.h>
#include <sys/sx.h>
+#include <sys/umtxvar.h>
#include <sys/unistd.h>
#include <sys/wait.h>
@@ -436,4 +437,10 @@
if (error != 0)
linux_msg(td, "futex stuff in thread_detach failed.");
}
+
+ /*
+ * Do not rely on the robust list which is maintained by userspace,
+ * cleanup remaining pi (if any) after release_futexes anyway.
+ */
+ umtx_thread_exit(td);
}
diff --git a/sys/compat/linux/linux_futex.c b/sys/compat/linux/linux_futex.c
--- a/sys/compat/linux/linux_futex.c
+++ b/sys/compat/linux/linux_futex.c
@@ -71,6 +71,7 @@
#include <compat/linux/linux_dtrace.h>
#include <compat/linux/linux_emul.h>
#include <compat/linux/linux_futex.h>
+#include <compat/linux/linux_misc.h>
#include <compat/linux/linux_timer.h>
#include <compat/linux/linux_util.h>
@@ -92,9 +93,6 @@
"uint32_t", "uint32_t", "uint32_t *", "struct l_timespec *");
LIN_SDT_PROBE_DEFINE5(futex, linux_futex, debug_wake_op, "uint32_t *",
"int", "uint32_t", "uint32_t *", "uint32_t");
-LIN_SDT_PROBE_DEFINE0(futex, linux_futex, unimplemented_lock_pi);
-LIN_SDT_PROBE_DEFINE0(futex, linux_futex, unimplemented_unlock_pi);
-LIN_SDT_PROBE_DEFINE0(futex, linux_futex, unimplemented_trylock_pi);
LIN_SDT_PROBE_DEFINE0(futex, linux_futex, deprecated_requeue);
LIN_SDT_PROBE_DEFINE0(futex, linux_futex, unimplemented_wait_requeue_pi);
LIN_SDT_PROBE_DEFINE0(futex, linux_futex, unimplemented_cmp_requeue_pi);
@@ -134,6 +132,10 @@
static int linux_futex_wake(struct thread *, struct linux_futex_args *);
static int linux_futex_requeue(struct thread *, struct linux_futex_args *);
static int linux_futex_wakeop(struct thread *, struct linux_futex_args *);
+static int linux_futex_lock_pi(struct thread *, bool, struct linux_futex_args *);
+static int linux_futex_unlock_pi(struct thread *, bool,
+ struct linux_futex_args *);
+static int futex_wake_pi(struct thread *, uint32_t *, bool);
int
futex_wake(struct thread *td, uint32_t *uaddr, int val, bool shared)
@@ -150,6 +152,19 @@
return (linux_futex_wake(td, &args));
}
+static int
+futex_wake_pi(struct thread *td, uint32_t *uaddr, bool shared)
+{
+ struct linux_futex_args args;
+
+ bzero(&args, sizeof(args));
+ args.op = LINUX_FUTEX_UNLOCK_PI;
+ args.uaddr = uaddr;
+ args.flags = shared == true ? FUTEX_SHARED : 0;
+
+ return (linux_futex_unlock_pi(td, true, &args));
+}
+
static int
futex_atomic_op(struct thread *td, int encoded_op, uint32_t *uaddr)
{
@@ -306,37 +321,23 @@
return (linux_futex_wakeop(td, args));
case LINUX_FUTEX_LOCK_PI:
- /* not yet implemented */
- pem = pem_find(td->td_proc);
- if ((pem->flags & LINUX_XUNSUP_FUTEXPIOP) == 0) {
- linux_msg(td, "unsupported FUTEX_LOCK_PI");
- pem->flags |= LINUX_XUNSUP_FUTEXPIOP;
- LIN_SDT_PROBE0(futex, linux_futex,
- unimplemented_lock_pi);
- }
- return (ENOSYS);
+ args->clockrt = true;
+ LINUX_CTR2(sys_futex, "LOCKPI uaddr %p val 0x%x",
+ args->uaddr, args->val);
+
+ return (linux_futex_lock_pi(td, false, args));
case LINUX_FUTEX_UNLOCK_PI:
- /* not yet implemented */
- pem = pem_find(td->td_proc);
- if ((pem->flags & LINUX_XUNSUP_FUTEXPIOP) == 0) {
- linux_msg(td, "unsupported FUTEX_UNLOCK_PI");
- pem->flags |= LINUX_XUNSUP_FUTEXPIOP;
- LIN_SDT_PROBE0(futex, linux_futex,
- unimplemented_unlock_pi);
- }
- return (ENOSYS);
+ LINUX_CTR1(sys_futex, "UNLOCKPI uaddr %p",
+ args->uaddr);
+
+ return (linux_futex_unlock_pi(td, false, args));
case LINUX_FUTEX_TRYLOCK_PI:
- /* not yet implemented */
- pem = pem_find(td->td_proc);
- if ((pem->flags & LINUX_XUNSUP_FUTEXPIOP) == 0) {
- linux_msg(td, "unsupported FUTEX_TRYLOCK_PI");
- pem->flags |= LINUX_XUNSUP_FUTEXPIOP;
- LIN_SDT_PROBE0(futex, linux_futex,
- unimplemented_trylock_pi);
- }
- return (ENOSYS);
+ LINUX_CTR1(sys_futex, "TRYLOCKPI uaddr %p",
+ args->uaddr);
+
+ return (linux_futex_lock_pi(td, true, args));
case LINUX_FUTEX_WAIT_REQUEUE_PI:
/* not yet implemented */
@@ -368,6 +369,288 @@
}
}
+/*
+ * pi protocol:
+ * - 0 futex word value means unlocked.
+ * - TID futex word value means locked.
+ * Userspace uses atomic ops to lock/unlock these futexes without entering the
+ * kernel. If the lock-acquire fastpath fails, (transition from 0 to TID fails),
+ * then FUTEX_LOCK_PI is called.
+ * The kernel atomically set FUTEX_WAITERS bit in the futex word value, if no
+ * other waiters exists looks up the thread that owns the futex (it has put its
+ * own TID into the futex value) and made this thread the owner of the internal
+ * pi-aware lock object (mutex). Then the kernel tries to lock the internal lock
+ * object, on which it blocks. Once it returns, it has the mutex acquired, and it
+ * sets the futex value to its own TID and returns (futex value contains
+ * FUTEX_WAITERS|TID).
+ * The unlock fastpath would fail (because the FUTEX_WAITERS bit is set) and
+ * FUTEX_UNLOCK_PI will be called.
+ * If a futex is found to be held at exit time, the kernel sets the OWNER_DIED
+ * bit of the futex word and wakes up the next futex waiter (if any), WAITERS
+ * bit is preserved (if any).
+ * If OWNER_DIED bit is set the kernel sanity checks the futex word value against
+ * the internal futex state and if correct, acquire futex.
+ */
+static int
+linux_futex_lock_pi(struct thread *td, bool try, struct linux_futex_args *args)
+{
+ struct umtx_abs_timeout timo;
+ struct linux_emuldata *em;
+ struct umtx_pi *pi, *new_pi;
+ struct thread *td1;
+ struct umtx_q *uq;
+ int error, rv;
+ uint32_t owner, old_owner;
+
+ em = em_find(td);
+ uq = td->td_umtxq;
+ error = umtx_key_get(args->uaddr, TYPE_PI_FUTEX, GET_SHARED(args),
+ &uq->uq_key);
+ if (error != 0)
+ return (error);
+ if (args->ts != NULL)
+ linux_umtx_abs_timeout_init(&timo, args);
+
+ umtxq_lock(&uq->uq_key);
+ pi = umtx_pi_lookup(&uq->uq_key);
+ if (pi == NULL) {
+ new_pi = umtx_pi_alloc(M_NOWAIT);
+ if (new_pi == NULL) {
+ umtxq_unlock(&uq->uq_key);
+ new_pi = umtx_pi_alloc(M_WAITOK);
+ umtxq_lock(&uq->uq_key);
+ pi = umtx_pi_lookup(&uq->uq_key);
+ if (pi != NULL) {
+ umtx_pi_free(new_pi);
+ new_pi = NULL;
+ }
+ }
+ if (new_pi != NULL) {
+ new_pi->pi_key = uq->uq_key;
+ umtx_pi_insert(new_pi);
+ pi = new_pi;
+ }
+ }
+ umtx_pi_ref(pi);
+ umtxq_unlock(&uq->uq_key);
+ for (;;) {
+ /* Try uncontested case first. */
+ rv = casueword32(args->uaddr, 0, &owner, em->em_tid);
+ /* The acquire succeeded. */
+ if (rv == 0) {
+ error = 0;
+ break;
+ }
+ if (rv == -1) {
+ error = EFAULT;
+ break;
+ }
+
+ /*
+ * Avoid overwriting a possible error from sleep due
+ * to the pending signal with suspension check result.
+ */
+ if (error == 0) {
+ error = thread_check_susp(td, true);
+ if (error != 0)
+ break;
+ }
+
+ /* The futex word at *uaddr is already locked by the caller. */
+ if ((owner & FUTEX_TID_MASK) == em->em_tid) {
+ error = EDEADLK;
+ break;
+ }
+
+ /*
+ * Futex owner died, handle_futex_death() set the OWNER_DIED bit
+ * and clear tid. Try to acquire it.
+ */
+ if ((owner & FUTEX_TID_MASK) == 0) {
+ old_owner = owner;
+ owner = owner & (FUTEX_WAITERS | FUTEX_OWNER_DIED);
+ owner |= em->em_tid;
+ rv = casueword32(args->uaddr, old_owner, &owner, owner);
+ if (rv == -1) {
+ error = EFAULT;
+ break;
+ }
+ if (rv == 1) {
+ if (error == 0) {
+ error = thread_check_susp(td, true);
+ if (error != 0)
+ break;
+ }
+
+ /*
+ * If this failed the lock could
+ * changed, restart.
+ */
+ continue;
+ }
+
+ umtxq_lock(&uq->uq_key);
+ umtxq_busy(&uq->uq_key);
+ error = umtx_pi_claim(pi, td);
+ umtxq_unbusy(&uq->uq_key);
+ umtxq_unlock(&uq->uq_key);
+ if (error != 0) {
+ /*
+ * Since we're going to return an
+ * error, restore the futex to its
+ * previous, unowned state to avoid
+ * compounding the problem.
+ */
+ (void)casuword32(args->uaddr, owner, old_owner);
+ }
+ break;
+ }
+
+ /*
+ * Inconsistent state: OWNER_DIED is set and tid is not 0.
+ * Linux does some checks of futex state, we return EINVAL,
+ * as the user space can take care of this.
+ */
+ if ((owner & FUTEX_OWNER_DIED) != 0) {
+ error = EINVAL;
+ break;
+ }
+
+ if (try != 0) {
+ error = EBUSY;
+ break;
+ }
+
+ /*
+ * If we caught a signal, we have retried and now
+ * exit immediately.
+ */
+ if (error != 0)
+ break;
+
+ umtxq_lock(&uq->uq_key);
+ umtxq_busy(&uq->uq_key);
+ umtxq_unlock(&uq->uq_key);
+
+ /*
+ * Set the contested bit so that a release in user space knows
+ * to use the system call for unlock. If this fails either some
+ * one else has acquired the lock or it has been released.
+ */
+ rv = casueword32(args->uaddr, owner, &owner,
+ owner | FUTEX_WAITERS);
+ if (rv == -1) {
+ umtxq_unbusy_unlocked(&uq->uq_key);
+ error = EFAULT;
+ break;
+ }
+ if (rv == 1) {
+ umtxq_unbusy_unlocked(&uq->uq_key);
+ error = thread_check_susp(td, true);
+ if (error != 0)
+ break;
+
+ /*
+ * The lock changed and we need to retry or we
+ * lost a race to the thread unlocking the umtx.
+ */
+ continue;
+ }
+
+ /*
+ * Substitute Linux thread id by native thread id to
+ * avoid refactoring code of umtxq_sleep_pi().
+ */
+ td1 = linux_tdfind(td, owner & FUTEX_TID_MASK, -1);
+ if (td1 != NULL) {
+ owner = td1->td_tid;
+ PROC_UNLOCK(td1->td_proc);
+ } else {
+ umtxq_unbusy_unlocked(&uq->uq_key);
+ error = EINVAL;
+ break;
+ }
+
+ umtxq_lock(&uq->uq_key);
+
+ /* We set the contested bit, sleep. */
+ error = umtxq_sleep_pi(uq, pi, owner, "futexp",
+ args->ts == NULL ? NULL : &timo,
+ (args->flags & FUTEX_SHARED) != 0);
+ if (error != 0)
+ continue;
+
+ error = thread_check_susp(td, false);
+ if (error != 0)
+ break;
+ }
+
+ umtxq_lock(&uq->uq_key);
+ umtx_pi_unref(pi);
+ umtxq_unlock(&uq->uq_key);
+ umtx_key_release(&uq->uq_key);
+ return (error);
+}
+
+static int
+linux_futex_unlock_pi(struct thread *td, bool rb, struct linux_futex_args *args)
+{
+ struct linux_emuldata *em;
+ struct umtx_key key;
+ uint32_t old, owner, new_owner;
+ int count, error;
+
+ em = em_find(td);
+
+ /*
+ * Make sure we own this mtx.
+ */
+ error = fueword32(args->uaddr, &owner);
+ if (error == -1)
+ return (EFAULT);
+ if (!rb && (owner & FUTEX_TID_MASK) != em->em_tid)
+ return (EPERM);
+
+ error = umtx_key_get(args->uaddr, TYPE_PI_FUTEX, GET_SHARED(args), &key);
+ if (error != 0)
+ return (error);
+ umtxq_lock(&key);
+ umtxq_busy(&key);
+ error = umtx_pi_drop(td, &key, rb, &count);
+ if (error != 0 || rb) {
+ umtxq_unbusy(&key);
+ umtxq_unlock(&key);
+ umtx_key_release(&key);
+ return (error);
+ }
+ umtxq_unlock(&key);
+
+ /*
+ * When unlocking the futex, it must be marked as unowned if
+ * there is zero or one thread only waiting for it.
+ * Otherwise, it must be marked as contested.
+ */
+ if (count > 1)
+ new_owner = FUTEX_WAITERS;
+ else
+ new_owner = 0;
+
+again:
+ error = casueword32(args->uaddr, owner, &old, new_owner);
+ if (error == 1) {
+ error = thread_check_susp(td, false);
+ if (error == 0)
+ goto again;
+ }
+ umtxq_unbusy_unlocked(&key);
+ umtx_key_release(&key);
+ if (error == -1)
+ return (EFAULT);
+ if (error == 0 && old != owner)
+ return (EINVAL);
+ return (error);
+}
+
static int
linux_futex_wakeop(struct thread *td, struct linux_futex_args *args)
{
@@ -576,6 +859,7 @@
switch (args->op & LINUX_FUTEX_CMD_MASK) {
case LINUX_FUTEX_WAIT:
case LINUX_FUTEX_WAIT_BITSET:
+ case LINUX_FUTEX_LOCK_PI:
if (args->timeout != NULL) {
error = copyin(args->timeout, &lts, sizeof(lts));
if (error != 0)
@@ -611,6 +895,7 @@
switch (args->op & LINUX_FUTEX_CMD_MASK) {
case LINUX_FUTEX_WAIT:
case LINUX_FUTEX_WAIT_BITSET:
+ case LINUX_FUTEX_LOCK_PI:
if (args->timeout != NULL) {
error = copyin(args->timeout, &lts, sizeof(lts));
if (error != 0)
@@ -721,6 +1006,10 @@
error = futex_wake(curthread, uaddr, 1, true);
if (error != 0)
return (error);
+ } else if (pi && (uval & FUTEX_WAITERS)) {
+ error = futex_wake_pi(curthread, uaddr, true);
+ if (error != 0)
+ return (error);
}
}

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