/*- * Copyright (c) 2004 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. */ /* * Implementation of sleep queues used to hold queue of threads blocked on * a wait channel. Sleep queues different from turnstiles in that wait * channels are not owned by anyone, so there is no priority propagation. * Sleep queues can also provide a timeout and can also be interrupted by * signals. That said, there are several similarities between the turnstile * and sleep queue implementations. (Note: turnstiles were implemented * first.) For example, both use a hash table of the same size where each * bucket is referred to as a "chain" that contains both a spin lock and * a linked list of queues. An individual queue is located by using a hash * to pick a chain, locking the chain, and then walking the chain searching * for the queue. This means that a wait channel object does not need to * embed it's queue head just as locks do not embed their turnstile queue * head. Threads also carry around a sleep queue that they lend to the * wait channel when blocking. Just as in turnstiles, the queue includes * a free list of the sleep queues of other threads blocked on the same * wait channel in the case of multiple waiters. * * Some additional functionality provided by sleep queues include the * ability to set a timeout. The timeout is managed using a per-thread * callout that resumes a thread if it is asleep. A thread may also * catch signals while it is asleep (aka an interruptible sleep). The * signal code uses sleepq_abort() to interrupt a sleeping thread. Finally, * sleep queues also provide some extra assertions. One is not allowed to * mix the sleep/wakeup and cv APIs for a given wait channel. Also, one * must consistently use the same lock to synchronize with a wait channel, * though this check is currently only a warning for sleep/wakeup due to * pre-existing abuse of that API. The same lock must also be held when * awakening threads, though that is currently only enforced for condition * variables. */ #include __FBSDID("$FreeBSD$"); #include "opt_sleepqueue_profiling.h" #include "opt_ddb.h" #include #include #include #include #include #include #include #include #include #include #include #include #ifdef DDB #include #endif /* * Constants for the hash table of sleep queue chains. These constants are * the same ones that 4BSD (and possibly earlier versions of BSD) used. * Basically, we ignore the lower 8 bits of the address since most wait * channel pointers are aligned and only look at the next 7 bits for the * hash. SC_TABLESIZE must be a power of two for SC_MASK to work properly. */ #define SC_TABLESIZE 128 /* Must be power of 2. */ #define SC_MASK (SC_TABLESIZE - 1) #define SC_SHIFT 8 #define SC_HASH(wc) (((uintptr_t)(wc) >> SC_SHIFT) & SC_MASK) #define SC_LOOKUP(wc) &sleepq_chains[SC_HASH(wc)] #define NR_SLEEPQS 2 /* * There two different lists of sleep queues. Both lists are connected * via the sq_hash entries. The first list is the sleep queue chain list * that a sleep queue is on when it is attached to a wait channel. The * second list is the free list hung off of a sleep queue that is attached * to a wait channel. * * Each sleep queue also contains the wait channel it is attached to, the * list of threads blocked on that wait channel, flags specific to the * wait channel, and the lock used to synchronize with a wait channel. * The flags are used to catch mismatches between the various consumers * of the sleep queue API (e.g. sleep/wakeup and condition variables). * The lock pointer is only used when invariants are enabled for various * debugging checks. * * Locking key: * c - sleep queue chain lock */ struct sleepqueue { TAILQ_HEAD(, thread) sq_blocked[NR_SLEEPQS]; /* (c) Blocked threads. */ LIST_ENTRY(sleepqueue) sq_hash; /* (c) Chain and free list. */ LIST_HEAD(, sleepqueue) sq_free; /* (c) Free queues. */ void *sq_wchan; /* (c) Wait channel. */ #ifdef INVARIANTS int sq_type; /* (c) Queue type. */ struct lock_object *sq_lock; /* (c) Associated lock. */ #endif }; struct sleepqueue_chain { LIST_HEAD(, sleepqueue) sc_queues; /* List of sleep queues. */ struct mtx sc_lock; /* Spin lock for this chain. */ #ifdef SLEEPQUEUE_PROFILING u_int sc_depth; /* Length of sc_queues. */ u_int sc_max_depth; /* Max length of sc_queues. */ #endif }; #ifdef SLEEPQUEUE_PROFILING u_int sleepq_max_depth; SYSCTL_NODE(_debug, OID_AUTO, sleepq, CTLFLAG_RD, 0, "sleepq profiling"); SYSCTL_NODE(_debug_sleepq, OID_AUTO, chains, CTLFLAG_RD, 0, "sleepq chain stats"); SYSCTL_UINT(_debug_sleepq, OID_AUTO, max_depth, CTLFLAG_RD, &sleepq_max_depth, 0, "maxmimum depth achieved of a single chain"); #endif static struct sleepqueue_chain sleepq_chains[SC_TABLESIZE]; static uma_zone_t sleepq_zone; /* * Prototypes for non-exported routines. */ static int sleepq_catch_signals(void *wchan); static int sleepq_check_signals(void); static int sleepq_check_timeout(void); #ifdef INVARIANTS static void sleepq_dtor(void *mem, int size, void *arg); #endif static int sleepq_init(void *mem, int size, int flags); static void sleepq_resume_thread(struct sleepqueue *sq, struct thread *td, int pri); static void sleepq_switch(void *wchan); static void sleepq_timeout(void *arg); /* * Early initialization of sleep queues that is called from the sleepinit() * SYSINIT. */ void init_sleepqueues(void) { #ifdef SLEEPQUEUE_PROFILING struct sysctl_oid *chain_oid; char chain_name[10]; #endif int i; for (i = 0; i < SC_TABLESIZE; i++) { LIST_INIT(&sleepq_chains[i].sc_queues); mtx_init(&sleepq_chains[i].sc_lock, "sleepq chain", NULL, MTX_SPIN); #ifdef SLEEPQUEUE_PROFILING snprintf(chain_name, sizeof(chain_name), "%d", i); chain_oid = SYSCTL_ADD_NODE(NULL, SYSCTL_STATIC_CHILDREN(_debug_sleepq_chains), OID_AUTO, chain_name, CTLFLAG_RD, NULL, "sleepq chain stats"); SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO, "depth", CTLFLAG_RD, &sleepq_chains[i].sc_depth, 0, NULL); SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO, "max_depth", CTLFLAG_RD, &sleepq_chains[i].sc_max_depth, 0, NULL); #endif } sleepq_zone = uma_zcreate("SLEEPQUEUE", sizeof(struct sleepqueue), #ifdef INVARIANTS NULL, sleepq_dtor, sleepq_init, NULL, UMA_ALIGN_CACHE, 0); #else NULL, NULL, sleepq_init, NULL, UMA_ALIGN_CACHE, 0); #endif thread0.td_sleepqueue = sleepq_alloc(); } /* * Get a sleep queue for a new thread. */ struct sleepqueue * sleepq_alloc(void) { return (uma_zalloc(sleepq_zone, M_WAITOK)); } /* * Free a sleep queue when a thread is destroyed. */ void sleepq_free(struct sleepqueue *sq) { uma_zfree(sleepq_zone, sq); } /* * Lock the sleep queue chain associated with the specified wait channel. */ void sleepq_lock(void *wchan) { struct sleepqueue_chain *sc; sc = SC_LOOKUP(wchan); mtx_lock_spin(&sc->sc_lock); } /* * Look up the sleep queue associated with a given wait channel in the hash * table locking the associated sleep queue chain. If no queue is found in * the table, NULL is returned. */ struct sleepqueue * sleepq_lookup(void *wchan) { struct sleepqueue_chain *sc; struct sleepqueue *sq; KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__)); sc = SC_LOOKUP(wchan); mtx_assert(&sc->sc_lock, MA_OWNED); LIST_FOREACH(sq, &sc->sc_queues, sq_hash) if (sq->sq_wchan == wchan) return (sq); return (NULL); } /* * Unlock the sleep queue chain associated with a given wait channel. */ void sleepq_release(void *wchan) { struct sleepqueue_chain *sc; sc = SC_LOOKUP(wchan); mtx_unlock_spin(&sc->sc_lock); } /* * Places the current thread on the sleep queue for the specified wait * channel. If INVARIANTS is enabled, then it associates the passed in * lock with the sleepq to make sure it is held when that sleep queue is * woken up. */ void sleepq_add(void *wchan, struct lock_object *lock, const char *wmesg, int flags, int queue) { struct sleepqueue_chain *sc; struct sleepqueue *sq; struct thread *td; td = curthread; sc = SC_LOOKUP(wchan); mtx_assert(&sc->sc_lock, MA_OWNED); MPASS(td->td_sleepqueue != NULL); MPASS(wchan != NULL); MPASS((queue >= 0) && (queue < NR_SLEEPQS)); /* If this thread is not allowed to sleep, die a horrible death. */ KASSERT(!(td->td_pflags & TDP_NOSLEEPING), ("Trying sleep, but thread marked as sleeping prohibited")); /* Look up the sleep queue associated with the wait channel 'wchan'. */ sq = sleepq_lookup(wchan); /* * If the wait channel does not already have a sleep queue, use * this thread's sleep queue. Otherwise, insert the current thread * into the sleep queue already in use by this wait channel. */ if (sq == NULL) { #ifdef INVARIANTS int i; sq = td->td_sleepqueue; for (i = 0; i < NR_SLEEPQS; i++) KASSERT(TAILQ_EMPTY(&sq->sq_blocked[i]), ("thread's sleep queue %d is not empty", i)); KASSERT(LIST_EMPTY(&sq->sq_free), ("thread's sleep queue has a non-empty free list")); KASSERT(sq->sq_wchan == NULL, ("stale sq_wchan pointer")); sq->sq_lock = lock; sq->sq_type = flags & SLEEPQ_TYPE; #endif #ifdef SLEEPQUEUE_PROFILING sc->sc_depth++; if (sc->sc_depth > sc->sc_max_depth) { sc->sc_max_depth = sc->sc_depth; if (sc->sc_max_depth > sleepq_max_depth) sleepq_max_depth = sc->sc_max_depth; } #endif sq = td->td_sleepqueue; LIST_INSERT_HEAD(&sc->sc_queues, sq, sq_hash); sq->sq_wchan = wchan; } else { MPASS(wchan == sq->sq_wchan); MPASS(lock == sq->sq_lock); MPASS((flags & SLEEPQ_TYPE) == sq->sq_type); LIST_INSERT_HEAD(&sq->sq_free, td->td_sleepqueue, sq_hash); } TAILQ_INSERT_TAIL(&sq->sq_blocked[queue], td, td_slpq); td->td_sleepqueue = NULL; mtx_lock_spin(&sched_lock); td->td_sqqueue = queue; td->td_wchan = wchan; td->td_wmesg = wmesg; if (flags & SLEEPQ_INTERRUPTIBLE) { td->td_flags |= TDF_SINTR; td->td_flags &= ~TDF_SLEEPABORT; } mtx_unlock_spin(&sched_lock); } /* * Sets a timeout that will remove the current thread from the specified * sleep queue after timo ticks if the thread has not already been awakened. */ void sleepq_set_timeout(void *wchan, int timo) { struct sleepqueue_chain *sc; struct thread *td; td = curthread; sc = SC_LOOKUP(wchan); mtx_assert(&sc->sc_lock, MA_OWNED); MPASS(TD_ON_SLEEPQ(td)); MPASS(td->td_sleepqueue == NULL); MPASS(wchan != NULL); callout_reset(&td->td_slpcallout, timo, sleepq_timeout, td); } /* * Marks the pending sleep of the current thread as interruptible and * makes an initial check for pending signals before putting a thread * to sleep. Return with sleep queue and scheduler lock held. */ static int sleepq_catch_signals(void *wchan) { struct sleepqueue_chain *sc; struct sleepqueue *sq; struct thread *td; struct proc *p; struct sigacts *ps; int sig, ret; td = curthread; p = curproc; sc = SC_LOOKUP(wchan); mtx_assert(&sc->sc_lock, MA_OWNED); MPASS(wchan != NULL); CTR3(KTR_PROC, "sleepq catching signals: thread %p (pid %ld, %s)", (void *)td, (long)p->p_pid, p->p_comm); MPASS(td->td_flags & TDF_SINTR); mtx_unlock_spin(&sc->sc_lock); /* See if there are any pending signals for this thread. */ PROC_LOCK(p); ps = p->p_sigacts; mtx_lock(&ps->ps_mtx); sig = cursig(td); if (sig == 0) { mtx_unlock(&ps->ps_mtx); ret = thread_suspend_check(1); MPASS(ret == 0 || ret == EINTR || ret == ERESTART); } else { if (SIGISMEMBER(ps->ps_sigintr, sig)) ret = EINTR; else ret = ERESTART; mtx_unlock(&ps->ps_mtx); } if (ret == 0) { mtx_lock_spin(&sc->sc_lock); /* * Lock sched_lock before unlocking proc lock, * without this, we could lose a race. */ mtx_lock_spin(&sched_lock); PROC_UNLOCK(p); if (!(td->td_flags & TDF_INTERRUPT)) return (0); /* KSE threads tried unblocking us. */ ret = td->td_intrval; mtx_unlock_spin(&sched_lock); MPASS(ret == EINTR || ret == ERESTART); } else { PROC_UNLOCK(p); mtx_lock_spin(&sc->sc_lock); } /* * There were pending signals and this thread is still * on the sleep queue, remove it from the sleep queue. */ sq = sleepq_lookup(wchan); mtx_lock_spin(&sched_lock); if (TD_ON_SLEEPQ(td)) sleepq_resume_thread(sq, td, -1); return (ret); } /* * Switches to another thread if we are still asleep on a sleep queue and * drop the lock on the sleep queue chain. Returns with sched_lock held. */ static void sleepq_switch(void *wchan) { struct sleepqueue_chain *sc; struct thread *td; td = curthread; sc = SC_LOOKUP(wchan); mtx_assert(&sc->sc_lock, MA_OWNED); mtx_assert(&sched_lock, MA_OWNED); /* * If we have a sleep queue, then we've already been woken up, so * just return. */ if (td->td_sleepqueue != NULL) { MPASS(!TD_ON_SLEEPQ(td)); mtx_unlock_spin(&sc->sc_lock); return; } /* * Otherwise, actually go to sleep. */ mtx_unlock_spin(&sc->sc_lock); sched_sleep(td); TD_SET_SLEEPING(td); mi_switch(SW_VOL, NULL); KASSERT(TD_IS_RUNNING(td), ("running but not TDS_RUNNING")); CTR3(KTR_PROC, "sleepq resume: thread %p (pid %ld, %s)", (void *)td, (long)td->td_proc->p_pid, (void *)td->td_proc->p_comm); } /* * Check to see if we timed out. */ static int sleepq_check_timeout(void) { struct thread *td; mtx_assert(&sched_lock, MA_OWNED); td = curthread; /* * If TDF_TIMEOUT is set, we timed out. */ if (td->td_flags & TDF_TIMEOUT) { td->td_flags &= ~TDF_TIMEOUT; return (EWOULDBLOCK); } /* * If TDF_TIMOFAIL is set, the timeout ran after we had * already been woken up. */ if (td->td_flags & TDF_TIMOFAIL) td->td_flags &= ~TDF_TIMOFAIL; /* * If callout_stop() fails, then the timeout is running on * another CPU, so synchronize with it to avoid having it * accidentally wake up a subsequent sleep. */ else if (callout_stop(&td->td_slpcallout) == 0) { td->td_flags |= TDF_TIMEOUT; TD_SET_SLEEPING(td); mi_switch(SW_INVOL, NULL); } return (0); } /* * Check to see if we were awoken by a signal. */ static int sleepq_check_signals(void) { struct thread *td; mtx_assert(&sched_lock, MA_OWNED); td = curthread; /* We are no longer in an interruptible sleep. */ if (td->td_flags & TDF_SINTR) td->td_flags &= ~TDF_SINTR; if (td->td_flags & TDF_SLEEPABORT) { td->td_flags &= ~TDF_SLEEPABORT; return (td->td_intrval); } if (td->td_flags & TDF_INTERRUPT) return (td->td_intrval); return (0); } /* * Block the current thread until it is awakened from its sleep queue. */ void sleepq_wait(void *wchan) { MPASS(!(curthread->td_flags & TDF_SINTR)); mtx_lock_spin(&sched_lock); sleepq_switch(wchan); mtx_unlock_spin(&sched_lock); } /* * Block the current thread until it is awakened from its sleep queue * or it is interrupted by a signal. */ int sleepq_wait_sig(void *wchan) { int rcatch; int rval; rcatch = sleepq_catch_signals(wchan); if (rcatch == 0) sleepq_switch(wchan); else sleepq_release(wchan); rval = sleepq_check_signals(); mtx_unlock_spin(&sched_lock); if (rcatch) return (rcatch); return (rval); } /* * Block the current thread until it is awakened from its sleep queue * or it times out while waiting. */ int sleepq_timedwait(void *wchan) { int rval; MPASS(!(curthread->td_flags & TDF_SINTR)); mtx_lock_spin(&sched_lock); sleepq_switch(wchan); rval = sleepq_check_timeout(); mtx_unlock_spin(&sched_lock); return (rval); } /* * Block the current thread until it is awakened from its sleep queue, * it is interrupted by a signal, or it times out waiting to be awakened. */ int sleepq_timedwait_sig(void *wchan) { int rcatch, rvalt, rvals; rcatch = sleepq_catch_signals(wchan); if (rcatch == 0) sleepq_switch(wchan); else sleepq_release(wchan); rvalt = sleepq_check_timeout(); rvals = sleepq_check_signals(); mtx_unlock_spin(&sched_lock); if (rcatch) return (rcatch); if (rvals) return (rvals); return (rvalt); } /* * Removes a thread from a sleep queue and makes it * runnable. */ static void sleepq_resume_thread(struct sleepqueue *sq, struct thread *td, int pri) { struct sleepqueue_chain *sc; MPASS(td != NULL); MPASS(sq->sq_wchan != NULL); MPASS(td->td_wchan == sq->sq_wchan); MPASS(td->td_sqqueue < NR_SLEEPQS && td->td_sqqueue >= 0); sc = SC_LOOKUP(sq->sq_wchan); mtx_assert(&sc->sc_lock, MA_OWNED); mtx_assert(&sched_lock, MA_OWNED); /* Remove the thread from the queue. */ TAILQ_REMOVE(&sq->sq_blocked[td->td_sqqueue], td, td_slpq); /* * Get a sleep queue for this thread. If this is the last waiter, * use the queue itself and take it out of the chain, otherwise, * remove a queue from the free list. */ if (LIST_EMPTY(&sq->sq_free)) { td->td_sleepqueue = sq; #ifdef INVARIANTS sq->sq_wchan = NULL; #endif #ifdef SLEEPQUEUE_PROFILING sc->sc_depth--; #endif } else td->td_sleepqueue = LIST_FIRST(&sq->sq_free); LIST_REMOVE(td->td_sleepqueue, sq_hash); td->td_wmesg = NULL; td->td_wchan = NULL; td->td_flags &= ~TDF_SINTR; /* * Note that thread td might not be sleeping if it is running * sleepq_catch_signals() on another CPU or is blocked on * its proc lock to check signals. It doesn't hurt to clear * the sleeping flag if it isn't set though, so we just always * do it. However, we can't assert that it is set. */ CTR3(KTR_PROC, "sleepq_wakeup: thread %p (pid %ld, %s)", (void *)td, (long)td->td_proc->p_pid, td->td_proc->p_comm); TD_CLR_SLEEPING(td); /* Adjust priority if requested. */ MPASS(pri == -1 || (pri >= PRI_MIN && pri <= PRI_MAX)); if (pri != -1 && td->td_priority > pri) sched_prio(td, pri); setrunnable(td); } #ifdef INVARIANTS /* * UMA zone item deallocator. */ static void sleepq_dtor(void *mem, int size, void *arg) { struct sleepqueue *sq; int i; sq = mem; for (i = 0; i < NR_SLEEPQS; i++) MPASS(TAILQ_EMPTY(&sq->sq_blocked[i])); } #endif /* * UMA zone item initializer. */ static int sleepq_init(void *mem, int size, int flags) { struct sleepqueue *sq; int i; bzero(mem, size); sq = mem; for (i = 0; i < NR_SLEEPQS; i++) TAILQ_INIT(&sq->sq_blocked[i]); LIST_INIT(&sq->sq_free); return (0); } /* * Find the highest priority thread sleeping on a wait channel and resume it. */ void sleepq_signal(void *wchan, int flags, int pri, int queue) { struct sleepqueue *sq; struct thread *td, *besttd; CTR2(KTR_PROC, "sleepq_signal(%p, %d)", wchan, flags); KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__)); MPASS((queue >= 0) && (queue < NR_SLEEPQS)); sq = sleepq_lookup(wchan); if (sq == NULL) { sleepq_release(wchan); return; } KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE), ("%s: mismatch between sleep/wakeup and cv_*", __func__)); /* * Find the highest priority thread on the queue. If there is a * tie, use the thread that first appears in the queue as it has * been sleeping the longest since threads are always added to * the tail of sleep queues. */ besttd = NULL; TAILQ_FOREACH(td, &sq->sq_blocked[queue], td_slpq) { if (besttd == NULL || td->td_priority < besttd->td_priority) besttd = td; } MPASS(besttd != NULL); mtx_lock_spin(&sched_lock); sleepq_resume_thread(sq, besttd, pri); mtx_unlock_spin(&sched_lock); sleepq_release(wchan); } /* * Resume all threads sleeping on a specified wait channel. */ void sleepq_broadcast(void *wchan, int flags, int pri, int queue) { struct sleepqueue *sq; CTR2(KTR_PROC, "sleepq_broadcast(%p, %d)", wchan, flags); KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__)); MPASS((queue >= 0) && (queue < NR_SLEEPQS)); sq = sleepq_lookup(wchan); if (sq == NULL) { sleepq_release(wchan); return; } KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE), ("%s: mismatch between sleep/wakeup and cv_*", __func__)); /* Resume all blocked threads on the sleep queue. */ mtx_lock_spin(&sched_lock); while (!TAILQ_EMPTY(&sq->sq_blocked[queue])) sleepq_resume_thread(sq, TAILQ_FIRST(&sq->sq_blocked[queue]), pri); mtx_unlock_spin(&sched_lock); sleepq_release(wchan); } /* * Time sleeping threads out. When the timeout expires, the thread is * removed from the sleep queue and made runnable if it is still asleep. */ static void sleepq_timeout(void *arg) { struct sleepqueue *sq; struct thread *td; void *wchan; td = arg; CTR3(KTR_PROC, "sleepq_timeout: thread %p (pid %ld, %s)", (void *)td, (long)td->td_proc->p_pid, (void *)td->td_proc->p_comm); /* * First, see if the thread is asleep and get the wait channel if * it is. */ mtx_lock_spin(&sched_lock); if (TD_ON_SLEEPQ(td)) { wchan = td->td_wchan; mtx_unlock_spin(&sched_lock); sleepq_lock(wchan); sq = sleepq_lookup(wchan); mtx_lock_spin(&sched_lock); } else { wchan = NULL; sq = NULL; } /* * At this point, if the thread is still on the sleep queue, * we have that sleep queue locked as it cannot migrate sleep * queues while we dropped sched_lock. If it had resumed and * was on another CPU while the lock was dropped, it would have * seen that TDF_TIMEOUT and TDF_TIMOFAIL are clear and the * call to callout_stop() to stop this routine would have failed * meaning that it would have already set TDF_TIMEOUT to * synchronize with this function. */ if (TD_ON_SLEEPQ(td)) { MPASS(td->td_wchan == wchan); MPASS(sq != NULL); td->td_flags |= TDF_TIMEOUT; sleepq_resume_thread(sq, td, -1); mtx_unlock_spin(&sched_lock); sleepq_release(wchan); return; } else if (wchan != NULL) sleepq_release(wchan); /* * Now check for the edge cases. First, if TDF_TIMEOUT is set, * then the other thread has already yielded to us, so clear * the flag and resume it. If TDF_TIMEOUT is not set, then the * we know that the other thread is not on a sleep queue, but it * hasn't resumed execution yet. In that case, set TDF_TIMOFAIL * to let it know that the timeout has already run and doesn't * need to be canceled. */ if (td->td_flags & TDF_TIMEOUT) { MPASS(TD_IS_SLEEPING(td)); td->td_flags &= ~TDF_TIMEOUT; TD_CLR_SLEEPING(td); setrunnable(td); } else td->td_flags |= TDF_TIMOFAIL; mtx_unlock_spin(&sched_lock); } /* * Resumes a specific thread from the sleep queue associated with a specific * wait channel if it is on that queue. */ void sleepq_remove(struct thread *td, void *wchan) { struct sleepqueue *sq; /* * Look up the sleep queue for this wait channel, then re-check * that the thread is asleep on that channel, if it is not, then * bail. */ MPASS(wchan != NULL); sleepq_lock(wchan); sq = sleepq_lookup(wchan); mtx_lock_spin(&sched_lock); if (!TD_ON_SLEEPQ(td) || td->td_wchan != wchan) { mtx_unlock_spin(&sched_lock); sleepq_release(wchan); return; } MPASS(sq != NULL); /* Thread is asleep on sleep queue sq, so wake it up. */ sleepq_resume_thread(sq, td, -1); sleepq_release(wchan); mtx_unlock_spin(&sched_lock); } /* * Abort a thread as if an interrupt had occurred. Only abort * interruptible waits (unfortunately it isn't safe to abort others). * * XXX: What in the world does the comment below mean? * Also, whatever the signal code does... */ void sleepq_abort(struct thread *td, int intrval) { void *wchan; mtx_assert(&sched_lock, MA_OWNED); MPASS(TD_ON_SLEEPQ(td)); MPASS(td->td_flags & TDF_SINTR); MPASS(intrval == EINTR || intrval == ERESTART); /* * If the TDF_TIMEOUT flag is set, just leave. A * timeout is scheduled anyhow. */ if (td->td_flags & TDF_TIMEOUT) return; CTR3(KTR_PROC, "sleepq_abort: thread %p (pid %ld, %s)", (void *)td, (long)td->td_proc->p_pid, (void *)td->td_proc->p_comm); wchan = td->td_wchan; if (wchan != NULL) { td->td_intrval = intrval; td->td_flags |= TDF_SLEEPABORT; } mtx_unlock_spin(&sched_lock); sleepq_remove(td, wchan); mtx_lock_spin(&sched_lock); } #ifdef DDB DB_SHOW_COMMAND(sleepq, db_show_sleepqueue) { struct sleepqueue_chain *sc; struct sleepqueue *sq; #ifdef INVARIANTS struct lock_object *lock; #endif struct thread *td; void *wchan; int i; if (!have_addr) return; /* * First, see if there is an active sleep queue for the wait channel * indicated by the address. */ wchan = (void *)addr; sc = SC_LOOKUP(wchan); LIST_FOREACH(sq, &sc->sc_queues, sq_hash) if (sq->sq_wchan == wchan) goto found; /* * Second, see if there is an active sleep queue at the address * indicated. */ for (i = 0; i < SC_TABLESIZE; i++) LIST_FOREACH(sq, &sleepq_chains[i].sc_queues, sq_hash) { if (sq == (struct sleepqueue *)addr) goto found; } db_printf("Unable to locate a sleep queue via %p\n", (void *)addr); return; found: db_printf("Wait channel: %p\n", sq->sq_wchan); #ifdef INVARIANTS db_printf("Queue type: %d\n", sq->sq_type); if (sq->sq_lock) { lock = sq->sq_lock; db_printf("Associated Interlock: %p - (%s) %s\n", lock, LOCK_CLASS(lock)->lc_name, lock->lo_name); } #endif db_printf("Blocked threads:\n"); for (i = 0; i < NR_SLEEPQS; i++) { db_printf("\nQueue[%d]:\n", i); if (TAILQ_EMPTY(&sq->sq_blocked[i])) db_printf("\tempty\n"); else TAILQ_FOREACH(td, &sq->sq_blocked[0], td_slpq) { db_printf("\t%p (tid %d, pid %d, \"%s\")\n", td, td->td_tid, td->td_proc->p_pid, td->td_name[i] != '\0' ? td->td_name : td->td_proc->p_comm); } } } /* Alias 'show sleepqueue' to 'show sleepq'. */ DB_SET(sleepqueue, db_show_sleepqueue, db_show_cmd_set, 0, NULL); #endif