94f0972bec
suspension code. When a thread A is going to sleep, it calls sleepq_catch_signals() to detect any pending signals or thread suspension request, if nothing happens, it returns without holding process lock or scheduler lock, this opens a race window which allows thread B to come in and do process suspension work, however since A is still at running state, thread B can do nothing to A, thread A continues, and puts itself into actually sleeping state, but B has never seen it, and it sits there forever until B is woken up by other threads sometimes later(this can be very long delay or never happen). Fix this bug by forcing sleepq_catch_signals to return with scheduler lock held. Fix sleepq_abort() by passing it an interrupted code, previously, it worked as wakeup_one(), and the interruption can not be identified correctly by sleep queue code when the sleeping thread is resumed. Let thread_suspend_check() returns EINTR or ERESTART, so sleep queue no longer has to use SIGSTOP as a hack to build a return value. Reviewed by: jhb MFC after: 1 week
384 lines
9.4 KiB
C
384 lines
9.4 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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WITNESS_SAVE_DECL(mp);
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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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cv_wait_unlock(cvp, mp);
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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. This function differs from cv_wait by
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* not aquiring the mutex after condition variable was signaled.
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*/
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void
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cv_wait_unlock(struct cv *cvp, struct mtx *mp)
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{
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struct thread *td;
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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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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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mtx_unlock(mp);
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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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PICKUP_GIANT();
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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;
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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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rval = sleepq_wait_sig(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. 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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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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rval = sleepq_timedwait_sig(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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* 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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