From d07a9130c61961c9c61c5204f35f878403bfe123 Mon Sep 17 00:00:00 2001 From: jhb Date: Fri, 27 Feb 2004 18:33:09 +0000 Subject: Add an implementation of a generic sleep queue abstraction that is used to queue threads sleeping on a wait channel similar to how turnstiles are used to queue threads waiting for a lock. This subsystem will be used as the backend for sleep/wakeup and condition variables initially. Eventually it will also be used to replace the ithread-specific iwait thread inhibitor. Sleep queues are also not locked by sched_lock, so this splits sched_lock up a bit further increasing concurrency within the scheduler. Sleep queues also natively support timeouts on sleeps and interruptible sleeps allowing for the reduction of a lot of duplicated code between the sleep/wakeup and condition variable implementations. For more details on the sleep queue implementation, check the comments in sys/sleepqueue.h and kern/subr_sleepqueue.c. --- sys/kern/subr_sleepqueue.c | 776 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 776 insertions(+) create mode 100644 sys/kern/subr_sleepqueue.c (limited to 'sys/kern/subr_sleepqueue.c') diff --git a/sys/kern/subr_sleepqueue.c b/sys/kern/subr_sleepqueue.c new file mode 100644 index 0000000..9b406ee --- /dev/null +++ b/sys/kern/subr_sleepqueue.c @@ -0,0 +1,776 @@ +/* + * 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 +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +/* + * 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)] + +/* + * 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; /* (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. */ + int sq_flags; /* (c) Flags. */ +#ifdef INVARIANTS + struct mtx *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. */ +}; + +static struct sleepqueue_chain sleepq_chains[SC_TABLESIZE]; + +MALLOC_DEFINE(M_SLEEPQUEUE, "sleep queues", "sleep queues"); + +/* + * Prototypes for non-exported routines. + */ +static int sleepq_check_timeout(void); +static void sleepq_switch(void *wchan); +static void sleepq_timeout(void *arg); +static void sleepq_wakeup_thread(struct sleepqueue *sq, struct thread *td, + int pri); + +/* + * Early initialization of sleep queues that is called from the sleepinit() + * SYSINIT. + */ +void +init_sleepqueues(void) +{ + 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); + } + thread0.td_sleepqueue = sleepq_alloc(); +} + +/* + * Malloc and initialize a new sleep queue for a new thread. + */ +struct sleepqueue * +sleepq_alloc(void) +{ + struct sleepqueue *sq; + + sq = malloc(sizeof(struct sleepqueue), M_SLEEPQUEUE, M_WAITOK | M_ZERO); + TAILQ_INIT(&sq->sq_blocked); + LIST_INIT(&sq->sq_free); + return (sq); +} + +/* + * Free a sleep queue when a thread is destroyed. + */ +void +sleepq_free(struct sleepqueue *sq) +{ + + MPASS(sq != NULL); + MPASS(TAILQ_EMPTY(&sq->sq_blocked)); + free(sq, M_SLEEPQUEUE); +} + +/* + * Look up the sleep queue associated with a given wait channel in the hash + * table locking the associated sleep queue chain. Return holdind the sleep + * queue chain lock. 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_lock_spin(&sc->sc_lock); + 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 sleepqueue 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(struct sleepqueue *sq, void *wchan, struct mtx *lock, + const char *wmesg, int flags) +{ + struct sleepqueue_chain *sc; + struct thread *td, *td1; + + td = curthread; + sc = SC_LOOKUP(wchan); + mtx_assert(&sc->sc_lock, MA_OWNED); + MPASS(td->td_sleepqueue != NULL); + MPASS(wchan != NULL); + + /* If the passed in sleep queue is NULL, use this thread's queue. */ + if (sq == NULL) { + sq = td->td_sleepqueue; + LIST_INSERT_HEAD(&sc->sc_queues, sq, sq_hash); + KASSERT(TAILQ_EMPTY(&sq->sq_blocked), + ("thread's sleep queue has a non-empty queue")); + 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_wchan = wchan; +#ifdef INVARIANTS + sq->sq_lock = lock; +#endif + sq->sq_flags = flags; + TAILQ_INSERT_TAIL(&sq->sq_blocked, td, td_slpq); + } else { + MPASS(wchan == sq->sq_wchan); +#ifdef INVARIANTS + if (flags & SLEEPQ_CONDVAR) + MPASS(lock == sq->sq_lock); + else if (lock != sq->sq_lock) { + /* + * When msleep() abusers are fixed this should + * change back to the simple MPASS() for all + * sleep queues. + */ + printf("Mismatched locks to msleep(%p, %s):\n", + wchan, wmesg); + printf(" old %p (%s), new %p (%s)\n", sq->sq_lock, + sq->sq_lock == NULL ? "null" : + sq->sq_lock->mtx_object.lo_name, lock, + lock == NULL ? "null" : + lock->mtx_object.lo_name); + backtrace(); + } +#endif + TAILQ_FOREACH(td1, &sq->sq_blocked, td_slpq) + if (td1->td_priority > td->td_priority) + break; + if (td1 != NULL) + TAILQ_INSERT_BEFORE(td1, td, td_slpq); + else + TAILQ_INSERT_TAIL(&sq->sq_blocked, td, td_slpq); + LIST_INSERT_HEAD(&sq->sq_free, td->td_sleepqueue, sq_hash); + } + td->td_sleepqueue = NULL; + mtx_lock_spin(&sched_lock); + td->td_wchan = wchan; + td->td_wmesg = wmesg; + 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(struct sleepqueue *sq, 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. + */ +int +sleepq_catch_signals(void *wchan) +{ + struct sleepqueue_chain *sc; + struct sleepqueue *sq; + struct thread *td; + struct proc *p; + int sig; + + td = curthread; + p = td->td_proc; + sc = SC_LOOKUP(wchan); + mtx_assert(&sc->sc_lock, MA_OWNED); + MPASS(td->td_sleepqueue == NULL); + MPASS(wchan != NULL); + CTR3(KTR_PROC, "sleepq catching signals: thread %p (pid %d, %s)", td, + p->p_pid, p->p_comm); + + /* Mark thread as being in an interruptible sleep. */ + mtx_lock_spin(&sched_lock); + MPASS(TD_ON_SLEEPQ(td)); + td->td_flags |= TDF_SINTR; + mtx_unlock_spin(&sched_lock); + sleepq_release(wchan); + + /* See if there are any pending signals for this thread. */ + PROC_LOCK(p); + mtx_lock(&p->p_sigacts->ps_mtx); + sig = cursig(td); + mtx_unlock(&p->p_sigacts->ps_mtx); + if (sig == 0 && thread_suspend_check(1)) + sig = SIGSTOP; + PROC_UNLOCK(p); + + /* + * If 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) && sig != 0) { + mtx_unlock_spin(&sched_lock); + sleepq_wakeup_thread(sq, td, -1); + } else + mtx_unlock_spin(&sched_lock); + return (sig); +} + +/* + * Switches to another thread if we are still asleep on a sleep queue and + * drop the lock on the sleepqueue 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); + + /* + * 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); + mtx_lock_spin(&sched_lock); + return; + } + + /* + * Otherwise, actually go to sleep. + */ + mtx_lock_spin(&sched_lock); + mtx_unlock_spin(&sc->sc_lock); + + sched_sleep(td); + TD_SET_SLEEPING(td); + mi_switch(SW_VOL); + KASSERT(TD_IS_RUNNING(td), ("running but not TDS_RUNNING")); + CTR3(KTR_PROC, "sleepq resume: thread %p (pid %d, %s)", td, + td->td_proc->p_pid, 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); + } + 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. */ + td->td_flags &= ~TDF_SINTR; + + /* If we were interrupted, return td_intrval. */ + if (td->td_flags & TDF_INTERRUPT) + return (td->td_intrval); + return (0); +} + +/* + * If we were in an interruptible sleep and we weren't interrupted and + * didn't timeout, check to see if there are any pending signals and + * which return value we should use if so. The return value from an + * earlier call to sleepq_catch_signals() should be passed in as the + * argument. + */ +int +sleepq_calc_signal_retval(int sig) +{ + struct thread *td; + struct proc *p; + int rval; + + td = curthread; + p = td->td_proc; + PROC_LOCK(p); + mtx_lock(&p->p_sigacts->ps_mtx); + /* XXX: Should we always be calling cursig()? */ + if (sig == 0) + sig = cursig(td); + if (sig != 0) { + if (SIGISMEMBER(p->p_sigacts->ps_sigintr, sig)) + rval = EINTR; + else + rval = ERESTART; + } else + rval = 0; + mtx_unlock(&p->p_sigacts->ps_mtx); + PROC_UNLOCK(p); + return (rval); +} + +/* + * Block the current thread until it is awakened from its sleep queue. + */ +void +sleepq_wait(void *wchan) +{ + + 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 rval; + + sleepq_switch(wchan); + rval = sleepq_check_signals(); + mtx_unlock_spin(&sched_lock); + 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 signal_caught) +{ + int rval; + + sleepq_switch(wchan); + rval = sleepq_check_timeout(); + mtx_unlock_spin(&sched_lock); + if (signal_caught) + return (0); + else + 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 signal_caught) +{ + int rvalt, rvals; + + sleepq_switch(wchan); + rvalt = sleepq_check_timeout(); + rvals = sleepq_check_signals(); + mtx_unlock_spin(&sched_lock); + if (signal_caught || rvalt == 0) + return (rvals); + else + return (rvalt); +} + +/* + * Removes a thread from a sleep queue and resumes it. + */ +static void +sleepq_wakeup_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); + sc = SC_LOOKUP(sq->sq_wchan); + mtx_assert(&sc->sc_lock, MA_OWNED); + + /* Remove the thread from the queue. */ + TAILQ_REMOVE(&sq->sq_blocked, 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 + } else + td->td_sleepqueue = LIST_FIRST(&sq->sq_free); + LIST_REMOVE(td->td_sleepqueue, sq_hash); + + /* + * Finish resuming the thread. + */ + mtx_lock_spin(&sched_lock); + CTR3(KTR_PROC, "sleepq_wakeup: thread %p (pid %d, %s)", td, + td->td_proc->p_pid, td->td_proc->p_comm); + td->td_wmesg = NULL; + td->td_wchan = NULL; + TD_CLR_SLEEPING(td); + + /* Adjust priority if requested. */ + MPASS(pri == -1 || (pri >= PRI_MIN && pri <= PRI_MAX)); + if (pri != -1 && td->td_priority > pri) + td->td_priority = pri; + setrunnable(td); + mtx_unlock_spin(&sched_lock); +} + +/* + * Find the highest priority thread sleeping on a wait channel and resume it. + */ +void +sleepq_signal(void *wchan, int flags, int pri) +{ + struct sleepqueue *sq; + + CTR2(KTR_PROC, "sleepq_signal(%p, %d)", wchan, flags); + KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__)); + sq = sleepq_lookup(wchan); + if (sq == NULL) { + sleepq_release(wchan); + return; + } + KASSERT(sq->sq_flags == flags, + ("%s: mismatch between sleep/wakeup and cv_*", __func__)); + /* XXX: Do for all sleep queues eventually. */ + if (flags & SLEEPQ_CONDVAR) + mtx_assert(sq->sq_lock, MA_OWNED); + sleepq_wakeup_thread(sq, TAILQ_FIRST(&sq->sq_blocked), pri); + sleepq_release(wchan); +} + +/* + * Resume all threads sleeping on a specified wait channel. + */ +void +sleepq_broadcast(void *wchan, int flags, int pri) +{ + struct sleepqueue *sq; + + CTR2(KTR_PROC, "sleepq_broadcast(%p, %d)", wchan, flags); + KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__)); + sq = sleepq_lookup(wchan); + if (sq == NULL) { + sleepq_release(wchan); + return; + } + KASSERT(sq->sq_flags == flags, + ("%s: mismatch between sleep/wakeup and cv_*", __func__)); + /* XXX: Do for all sleep queues eventually. */ + if (flags & SLEEPQ_CONDVAR) + mtx_assert(sq->sq_lock, MA_OWNED); + while (!TAILQ_EMPTY(&sq->sq_blocked)) + sleepq_wakeup_thread(sq, TAILQ_FIRST(&sq->sq_blocked), pri); + 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 = (struct thread *)arg; + CTR3(KTR_PROC, "sleepq_timeout: thread %p (pid %d, %s)", + td, td->td_proc->p_pid, 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); + 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_IS_SLEEPING(td)); + MPASS(td->td_wchan == wchan); + MPASS(sq != NULL); + td->td_flags |= TDF_TIMEOUT; + mtx_unlock_spin(&sched_lock); + sleepq_wakeup_thread(sq, td, -1); + 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) { + 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); + 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; + } + mtx_unlock_spin(&sched_lock); + MPASS(sq != NULL); + + /* Thread is asleep on sleep queue sq, so wake it up. */ + sleepq_wakeup_thread(sq, td, -1); + sleepq_release(wchan); +} + +/* + * Abort a thread as if an interrupt had occured. Only abort + * interruptable 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) +{ + void *wchan; + + mtx_assert(&sched_lock, MA_OWNED); + MPASS(TD_ON_SLEEPQ(td)); + MPASS(td->td_flags & TDF_SINTR); + + /* + * 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 %d, %s)", td, + td->td_proc->p_pid, td->td_proc->p_comm); + wchan = td->td_wchan; + mtx_unlock_spin(&sched_lock); + sleepq_remove(td, wchan); + mtx_lock_spin(&sched_lock); +} -- cgit v1.1