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2ff0e645d1
- Add a new _lock() call to each API that locks the associated chain lock for a lock_object pointer or wait channel. The _lookup() functions now require that the chain lock be locked via _lock() when they are called. - Change sleepq_add(), turnstile_wait() and turnstile_claim() to lookup the associated queue structure internally via _lookup() rather than accepting a pointer from the caller. For turnstiles, this means that the actual lookup of the turnstile in the hash table is only done when the thread actually blocks rather than being done on each loop iteration in _mtx_lock_sleep(). For sleep queues, this means that sleepq_lookup() is no longer used outside of the sleep queue code except to implement an assertion in cv_destroy(). - Change sleepq_broadcast() and sleepq_signal() to require that the chain lock is already required. For condition variables, this lets the cv_broadcast() and cv_signal() functions lock the sleep queue chain lock while testing the waiters count. This means that the waiters count internal to condition variables is no longer protected by the interlock mutex and cv_broadcast() and cv_signal() now no longer require that the interlock be held when they are called. This lets consumers of condition variables drop the lock before waking other threads which can result in fewer context switches. MFC after: 1 month
372 lines
9.1 KiB
C
372 lines
9.1 KiB
C
/*-
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* Copyright (c) 2000 Jake Burkholder <jake@freebsd.org>.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include "opt_ktrace.h"
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/lock.h>
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#include <sys/mutex.h>
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#include <sys/proc.h>
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#include <sys/kernel.h>
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#include <sys/ktr.h>
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#include <sys/condvar.h>
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#include <sys/sched.h>
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#include <sys/signalvar.h>
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#include <sys/sleepqueue.h>
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#include <sys/resourcevar.h>
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#ifdef KTRACE
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#include <sys/uio.h>
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#include <sys/ktrace.h>
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#endif
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/*
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* Common sanity checks for cv_wait* functions.
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*/
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#define CV_ASSERT(cvp, mp, td) do { \
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KASSERT((td) != NULL, ("%s: curthread NULL", __func__)); \
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KASSERT(TD_IS_RUNNING(td), ("%s: not TDS_RUNNING", __func__)); \
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KASSERT((cvp) != NULL, ("%s: cvp NULL", __func__)); \
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KASSERT((mp) != NULL, ("%s: mp NULL", __func__)); \
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mtx_assert((mp), MA_OWNED | MA_NOTRECURSED); \
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} while (0)
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/*
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* Initialize a condition variable. Must be called before use.
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*/
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void
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cv_init(struct cv *cvp, const char *desc)
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{
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cvp->cv_description = desc;
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cvp->cv_waiters = 0;
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}
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/*
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* Destroy a condition variable. The condition variable must be re-initialized
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* in order to be re-used.
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*/
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void
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cv_destroy(struct cv *cvp)
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{
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#ifdef INVARIANTS
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struct sleepqueue *sq;
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sleepq_lock(cvp);
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sq = sleepq_lookup(cvp);
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sleepq_release(cvp);
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KASSERT(sq == NULL, ("%s: associated sleep queue non-empty", __func__));
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#endif
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}
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/*
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* Wait on a condition variable. The current thread is placed on the condition
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* variable's wait queue and suspended. A cv_signal or cv_broadcast on the same
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* condition variable will resume the thread. The mutex is released before
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* sleeping and will be held on return. It is recommended that the mutex be
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* held when cv_signal or cv_broadcast are called.
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*/
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void
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cv_wait(struct cv *cvp, struct mtx *mp)
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{
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struct thread *td;
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WITNESS_SAVE_DECL(mp);
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td = curthread;
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#ifdef KTRACE
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if (KTRPOINT(td, KTR_CSW))
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ktrcsw(1, 0);
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#endif
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CV_ASSERT(cvp, mp, td);
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WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, &mp->mtx_object,
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"Waiting on \"%s\"", cvp->cv_description);
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WITNESS_SAVE(&mp->mtx_object, mp);
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if (cold || panicstr) {
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/*
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* During autoconfiguration, just give interrupts
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* a chance, then just return. Don't run any other
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* thread or panic below, in case this is the idle
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* process and already asleep.
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*/
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return;
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}
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sleepq_lock(cvp);
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cvp->cv_waiters++;
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DROP_GIANT();
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mtx_unlock(mp);
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sleepq_add(cvp, mp, cvp->cv_description, SLEEPQ_CONDVAR);
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sleepq_wait(cvp);
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#ifdef KTRACE
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if (KTRPOINT(td, KTR_CSW))
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ktrcsw(0, 0);
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#endif
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PICKUP_GIANT();
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mtx_lock(mp);
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WITNESS_RESTORE(&mp->mtx_object, mp);
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}
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/*
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* Wait on a condition variable, allowing interruption by signals. Return 0 if
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* the thread was resumed with cv_signal or cv_broadcast, EINTR or ERESTART if
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* a signal was caught. If ERESTART is returned the system call should be
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* restarted if possible.
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*/
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int
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cv_wait_sig(struct cv *cvp, struct mtx *mp)
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{
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struct thread *td;
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struct proc *p;
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int rval, sig;
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WITNESS_SAVE_DECL(mp);
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td = curthread;
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p = td->td_proc;
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#ifdef KTRACE
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if (KTRPOINT(td, KTR_CSW))
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ktrcsw(1, 0);
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#endif
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CV_ASSERT(cvp, mp, td);
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WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, &mp->mtx_object,
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"Waiting on \"%s\"", cvp->cv_description);
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WITNESS_SAVE(&mp->mtx_object, mp);
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if (cold || panicstr) {
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/*
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* After a panic, or during autoconfiguration, just give
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* interrupts a chance, then just return; don't run any other
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* procs or panic below, in case this is the idle process and
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* already asleep.
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*/
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return (0);
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}
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sleepq_lock(cvp);
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/*
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* Don't bother sleeping if we are exiting and not the exiting
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* thread or if our thread is marked as interrupted.
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*/
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mtx_lock_spin(&sched_lock);
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rval = thread_sleep_check(td);
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mtx_unlock_spin(&sched_lock);
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if (rval != 0) {
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sleepq_release(cvp);
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return (rval);
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}
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cvp->cv_waiters++;
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DROP_GIANT();
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mtx_unlock(mp);
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sleepq_add(cvp, mp, cvp->cv_description, SLEEPQ_CONDVAR |
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SLEEPQ_INTERRUPTIBLE);
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sig = sleepq_catch_signals(cvp);
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rval = sleepq_wait_sig(cvp);
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if (rval == 0)
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rval = sleepq_calc_signal_retval(sig);
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#ifdef KTRACE
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if (KTRPOINT(td, KTR_CSW))
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ktrcsw(0, 0);
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#endif
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PICKUP_GIANT();
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mtx_lock(mp);
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WITNESS_RESTORE(&mp->mtx_object, mp);
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return (rval);
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}
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/*
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* Wait on a condition variable for at most timo/hz seconds. Returns 0 if the
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* process was resumed by cv_signal or cv_broadcast, EWOULDBLOCK if the timeout
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* expires.
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*/
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int
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cv_timedwait(struct cv *cvp, struct mtx *mp, int timo)
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{
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struct thread *td;
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int rval;
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WITNESS_SAVE_DECL(mp);
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td = curthread;
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rval = 0;
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#ifdef KTRACE
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if (KTRPOINT(td, KTR_CSW))
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ktrcsw(1, 0);
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#endif
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CV_ASSERT(cvp, mp, td);
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WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, &mp->mtx_object,
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"Waiting on \"%s\"", cvp->cv_description);
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WITNESS_SAVE(&mp->mtx_object, mp);
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if (cold || panicstr) {
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/*
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* After a panic, or during autoconfiguration, just give
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* interrupts a chance, then just return; don't run any other
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* thread or panic below, in case this is the idle process and
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* already asleep.
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*/
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return 0;
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}
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sleepq_lock(cvp);
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cvp->cv_waiters++;
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DROP_GIANT();
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mtx_unlock(mp);
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sleepq_add(cvp, mp, cvp->cv_description, SLEEPQ_CONDVAR);
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sleepq_set_timeout(cvp, timo);
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rval = sleepq_timedwait(cvp);
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#ifdef KTRACE
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if (KTRPOINT(td, KTR_CSW))
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ktrcsw(0, 0);
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#endif
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PICKUP_GIANT();
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mtx_lock(mp);
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WITNESS_RESTORE(&mp->mtx_object, mp);
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return (rval);
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}
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/*
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* Wait on a condition variable for at most timo/hz seconds, allowing
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* interruption by signals. Returns 0 if the thread was resumed by cv_signal
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* or cv_broadcast, EWOULDBLOCK if the timeout expires, and EINTR or ERESTART if
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* a signal was caught.
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*/
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int
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cv_timedwait_sig(struct cv *cvp, struct mtx *mp, int timo)
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{
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struct thread *td;
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struct proc *p;
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int rval;
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int sig;
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WITNESS_SAVE_DECL(mp);
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td = curthread;
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p = td->td_proc;
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rval = 0;
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#ifdef KTRACE
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if (KTRPOINT(td, KTR_CSW))
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ktrcsw(1, 0);
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#endif
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CV_ASSERT(cvp, mp, td);
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WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, &mp->mtx_object,
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"Waiting on \"%s\"", cvp->cv_description);
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WITNESS_SAVE(&mp->mtx_object, mp);
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if (cold || panicstr) {
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/*
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* After a panic, or during autoconfiguration, just give
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* interrupts a chance, then just return; don't run any other
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* thread or panic below, in case this is the idle process and
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* already asleep.
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*/
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return 0;
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}
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sleepq_lock(cvp);
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/*
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* Don't bother sleeping if we are exiting and not the exiting
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* thread or if our thread is marked as interrupted.
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*/
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mtx_lock_spin(&sched_lock);
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rval = thread_sleep_check(td);
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mtx_unlock_spin(&sched_lock);
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if (rval != 0) {
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sleepq_release(cvp);
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return (rval);
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}
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cvp->cv_waiters++;
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DROP_GIANT();
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mtx_unlock(mp);
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sleepq_add(cvp, mp, cvp->cv_description, SLEEPQ_CONDVAR |
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SLEEPQ_INTERRUPTIBLE);
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sleepq_set_timeout(cvp, timo);
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sig = sleepq_catch_signals(cvp);
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rval = sleepq_timedwait_sig(cvp, sig != 0);
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if (rval == 0)
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rval = sleepq_calc_signal_retval(sig);
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#ifdef KTRACE
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if (KTRPOINT(td, KTR_CSW))
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ktrcsw(0, 0);
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#endif
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PICKUP_GIANT();
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mtx_lock(mp);
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WITNESS_RESTORE(&mp->mtx_object, mp);
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return (rval);
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}
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/*
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* Signal a condition variable, wakes up one waiting thread. Will also wakeup
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* the swapper if the process is not in memory, so that it can bring the
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* sleeping process in. Note that this may also result in additional threads
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* being made runnable. Should be called with the same mutex as was passed to
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* cv_wait held.
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*/
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void
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cv_signal(struct cv *cvp)
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{
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sleepq_lock(cvp);
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if (cvp->cv_waiters > 0) {
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cvp->cv_waiters--;
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sleepq_signal(cvp, SLEEPQ_CONDVAR, -1);
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} else
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sleepq_release(cvp);
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}
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/*
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* Broadcast a signal to a condition variable. Wakes up all waiting threads.
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* Should be called with the same mutex as was passed to cv_wait held.
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*/
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void
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cv_broadcastpri(struct cv *cvp, int pri)
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{
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sleepq_lock(cvp);
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if (cvp->cv_waiters > 0) {
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cvp->cv_waiters = 0;
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sleepq_broadcast(cvp, SLEEPQ_CONDVAR, pri);
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} else
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sleepq_release(cvp);
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}
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