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a13ec35b05
is "void *" (it isn't) or that the default promotion of pid_t is int. Instead, assume that casting "struct foo *" to "void *" and printing the result with %p is useful, and that all pid_t's are representable as longs. Fixed some minor style bugs (mainly spelling errors in comments).
799 lines
22 KiB
C
799 lines
22 KiB
C
/*
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* Copyright (c) 2004 John Baldwin <jhb@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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* 3. Neither the name of the author nor the names of any co-contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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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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/*
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* Implementation of sleep queues used to hold queue of threads blocked on
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* a wait channel. Sleep queues different from turnstiles in that wait
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* channels are not owned by anyone, so there is no priority propagation.
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* Sleep queues can also provide a timeout and can also be interrupted by
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* signals. That said, there are several similarities between the turnstile
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* and sleep queue implementations. (Note: turnstiles were implemented
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* first.) For example, both use a hash table of the same size where each
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* bucket is referred to as a "chain" that contains both a spin lock and
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* a linked list of queues. An individual queue is located by using a hash
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* to pick a chain, locking the chain, and then walking the chain searching
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* for the queue. This means that a wait channel object does not need to
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* embed it's queue head just as locks do not embed their turnstile queue
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* head. Threads also carry around a sleep queue that they lend to the
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* wait channel when blocking. Just as in turnstiles, the queue includes
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* a free list of the sleep queues of other threads blocked on the same
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* wait channel in the case of multiple waiters.
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*
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* Some additional functionality provided by sleep queues include the
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* ability to set a timeout. The timeout is managed using a per-thread
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* callout that resumes a thread if it is asleep. A thread may also
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* catch signals while it is asleep (aka an interruptible sleep). The
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* signal code uses sleepq_abort() to interrupt a sleeping thread. Finally,
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* sleep queues also provide some extra assertions. One is not allowed to
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* mix the sleep/wakeup and cv APIs for a given wait channel. Also, one
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* must consistently use the same lock to synchronize with a wait channel,
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* though this check is currently only a warning for sleep/wakeup due to
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* pre-existing abuse of that API. The same lock must also be held when
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* awakening threads, though that is currently only enforced for condition
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* variables.
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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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/kernel.h>
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#include <sys/ktr.h>
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#include <sys/malloc.h>
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#include <sys/mutex.h>
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#include <sys/proc.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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/*
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* Constants for the hash table of sleep queue chains. These constants are
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* the same ones that 4BSD (and possibly earlier versions of BSD) used.
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* Basically, we ignore the lower 8 bits of the address since most wait
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* channel pointers are aligned and only look at the next 7 bits for the
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* hash. SC_TABLESIZE must be a power of two for SC_MASK to work properly.
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*/
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#define SC_TABLESIZE 128 /* Must be power of 2. */
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#define SC_MASK (SC_TABLESIZE - 1)
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#define SC_SHIFT 8
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#define SC_HASH(wc) (((uintptr_t)(wc) >> SC_SHIFT) & SC_MASK)
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#define SC_LOOKUP(wc) &sleepq_chains[SC_HASH(wc)]
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/*
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* There two different lists of sleep queues. Both lists are connected
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* via the sq_hash entries. The first list is the sleep queue chain list
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* that a sleep queue is on when it is attached to a wait channel. The
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* second list is the free list hung off of a sleep queue that is attached
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* to a wait channel.
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*
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* Each sleep queue also contains the wait channel it is attached to, the
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* list of threads blocked on that wait channel, flags specific to the
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* wait channel, and the lock used to synchronize with a wait channel.
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* The flags are used to catch mismatches between the various consumers
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* of the sleep queue API (e.g. sleep/wakeup and condition variables).
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* The lock pointer is only used when invariants are enabled for various
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* debugging checks.
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*
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* Locking key:
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* c - sleep queue chain lock
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*/
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struct sleepqueue {
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TAILQ_HEAD(, thread) sq_blocked; /* (c) Blocked threads. */
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LIST_ENTRY(sleepqueue) sq_hash; /* (c) Chain and free list. */
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LIST_HEAD(, sleepqueue) sq_free; /* (c) Free queues. */
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void *sq_wchan; /* (c) Wait channel. */
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int sq_flags; /* (c) Flags. */
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#ifdef INVARIANTS
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struct mtx *sq_lock; /* (c) Associated lock. */
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#endif
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};
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struct sleepqueue_chain {
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LIST_HEAD(, sleepqueue) sc_queues; /* List of sleep queues. */
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struct mtx sc_lock; /* Spin lock for this chain. */
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};
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static struct sleepqueue_chain sleepq_chains[SC_TABLESIZE];
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MALLOC_DEFINE(M_SLEEPQUEUE, "sleep queues", "sleep queues");
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/*
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* Prototypes for non-exported routines.
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*/
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static int sleepq_check_timeout(void);
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static void sleepq_switch(void *wchan);
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static void sleepq_timeout(void *arg);
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static void sleepq_remove_thread(struct sleepqueue *sq, struct thread *td);
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static void sleepq_resume_thread(struct thread *td, int pri);
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/*
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* Early initialization of sleep queues that is called from the sleepinit()
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* SYSINIT.
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*/
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void
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init_sleepqueues(void)
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{
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int i;
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for (i = 0; i < SC_TABLESIZE; i++) {
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LIST_INIT(&sleepq_chains[i].sc_queues);
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mtx_init(&sleepq_chains[i].sc_lock, "sleepq chain", NULL,
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MTX_SPIN);
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}
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thread0.td_sleepqueue = sleepq_alloc();
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}
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/*
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* Malloc and initialize a new sleep queue for a new thread.
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*/
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struct sleepqueue *
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sleepq_alloc(void)
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{
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struct sleepqueue *sq;
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sq = malloc(sizeof(struct sleepqueue), M_SLEEPQUEUE, M_WAITOK | M_ZERO);
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TAILQ_INIT(&sq->sq_blocked);
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LIST_INIT(&sq->sq_free);
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return (sq);
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}
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/*
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* Free a sleep queue when a thread is destroyed.
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*/
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void
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sleepq_free(struct sleepqueue *sq)
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{
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MPASS(sq != NULL);
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MPASS(TAILQ_EMPTY(&sq->sq_blocked));
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free(sq, M_SLEEPQUEUE);
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}
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/*
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* Look up the sleep queue associated with a given wait channel in the hash
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* table locking the associated sleep queue chain. Return holdind the sleep
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* queue chain lock. If no queue is found in the table, NULL is returned.
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*/
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struct sleepqueue *
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sleepq_lookup(void *wchan)
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{
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struct sleepqueue_chain *sc;
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struct sleepqueue *sq;
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KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
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sc = SC_LOOKUP(wchan);
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mtx_lock_spin(&sc->sc_lock);
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LIST_FOREACH(sq, &sc->sc_queues, sq_hash)
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if (sq->sq_wchan == wchan)
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return (sq);
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return (NULL);
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}
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/*
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* Unlock the sleep queue chain associated with a given wait channel.
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*/
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void
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sleepq_release(void *wchan)
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{
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struct sleepqueue_chain *sc;
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sc = SC_LOOKUP(wchan);
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mtx_unlock_spin(&sc->sc_lock);
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}
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/*
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* Places the current thread on the sleepqueue for the specified wait
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* channel. If INVARIANTS is enabled, then it associates the passed in
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* lock with the sleepq to make sure it is held when that sleep queue is
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* woken up.
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*/
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void
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sleepq_add(struct sleepqueue *sq, void *wchan, struct mtx *lock,
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const char *wmesg, int flags)
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{
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struct sleepqueue_chain *sc;
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struct thread *td, *td1;
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td = curthread;
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sc = SC_LOOKUP(wchan);
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mtx_assert(&sc->sc_lock, MA_OWNED);
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MPASS(td->td_sleepqueue != NULL);
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MPASS(wchan != NULL);
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/* If the passed in sleep queue is NULL, use this thread's queue. */
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if (sq == NULL) {
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sq = td->td_sleepqueue;
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LIST_INSERT_HEAD(&sc->sc_queues, sq, sq_hash);
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KASSERT(TAILQ_EMPTY(&sq->sq_blocked),
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("thread's sleep queue has a non-empty queue"));
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KASSERT(LIST_EMPTY(&sq->sq_free),
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("thread's sleep queue has a non-empty free list"));
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KASSERT(sq->sq_wchan == NULL, ("stale sq_wchan pointer"));
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sq->sq_wchan = wchan;
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#ifdef INVARIANTS
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sq->sq_lock = lock;
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#endif
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sq->sq_flags = flags;
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TAILQ_INSERT_TAIL(&sq->sq_blocked, td, td_slpq);
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} else {
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MPASS(wchan == sq->sq_wchan);
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MPASS(lock == sq->sq_lock);
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TAILQ_FOREACH(td1, &sq->sq_blocked, td_slpq)
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if (td1->td_priority > td->td_priority)
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break;
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if (td1 != NULL)
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TAILQ_INSERT_BEFORE(td1, td, td_slpq);
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else
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TAILQ_INSERT_TAIL(&sq->sq_blocked, td, td_slpq);
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LIST_INSERT_HEAD(&sq->sq_free, td->td_sleepqueue, sq_hash);
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}
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td->td_sleepqueue = NULL;
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mtx_lock_spin(&sched_lock);
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td->td_wchan = wchan;
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td->td_wmesg = wmesg;
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mtx_unlock_spin(&sched_lock);
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}
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/*
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* Sets a timeout that will remove the current thread from the specified
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* sleep queue after timo ticks if the thread has not already been awakened.
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*/
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void
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sleepq_set_timeout(void *wchan, int timo)
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{
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struct sleepqueue_chain *sc;
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struct thread *td;
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td = curthread;
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sc = SC_LOOKUP(wchan);
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mtx_assert(&sc->sc_lock, MA_OWNED);
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MPASS(TD_ON_SLEEPQ(td));
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MPASS(td->td_sleepqueue == NULL);
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MPASS(wchan != NULL);
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callout_reset(&td->td_slpcallout, timo, sleepq_timeout, td);
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}
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/*
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* Marks the pending sleep of the current thread as interruptible and
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* makes an initial check for pending signals before putting a thread
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* to sleep.
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*/
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int
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sleepq_catch_signals(void *wchan)
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{
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struct sleepqueue_chain *sc;
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struct sleepqueue *sq;
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struct thread *td;
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struct proc *p;
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int do_upcall;
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int sig;
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do_upcall = 0;
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td = curthread;
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p = td->td_proc;
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sc = SC_LOOKUP(wchan);
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mtx_assert(&sc->sc_lock, MA_OWNED);
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MPASS(td->td_sleepqueue == NULL);
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MPASS(wchan != NULL);
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CTR3(KTR_PROC, "sleepq catching signals: thread %p (pid %ld, %s)",
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(void *)td, (long)p->p_pid, p->p_comm);
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/* Mark thread as being in an interruptible sleep. */
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mtx_lock_spin(&sched_lock);
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MPASS(TD_ON_SLEEPQ(td));
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td->td_flags |= TDF_SINTR;
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mtx_unlock_spin(&sched_lock);
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sleepq_release(wchan);
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/* See if there are any pending signals for this thread. */
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PROC_LOCK(p);
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mtx_lock(&p->p_sigacts->ps_mtx);
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sig = cursig(td);
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mtx_unlock(&p->p_sigacts->ps_mtx);
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if (sig == 0 && thread_suspend_check(1))
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sig = SIGSTOP;
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else
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do_upcall = thread_upcall_check(td);
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PROC_UNLOCK(p);
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/*
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* If there were pending signals and this thread is still on
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* the sleep queue, remove it from the sleep queue.
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*/
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sq = sleepq_lookup(wchan);
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mtx_lock_spin(&sched_lock);
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if (TD_ON_SLEEPQ(td) && (sig != 0 || do_upcall != 0)) {
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mtx_unlock_spin(&sched_lock);
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sleepq_remove_thread(sq, td);
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} else
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mtx_unlock_spin(&sched_lock);
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return (sig);
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}
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/*
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* Switches to another thread if we are still asleep on a sleep queue and
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* drop the lock on the sleepqueue chain. Returns with sched_lock held.
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*/
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static void
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sleepq_switch(void *wchan)
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{
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struct sleepqueue_chain *sc;
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struct thread *td;
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td = curthread;
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sc = SC_LOOKUP(wchan);
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mtx_assert(&sc->sc_lock, MA_OWNED);
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/*
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* If we have a sleep queue, then we've already been woken up, so
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* just return.
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*/
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if (td->td_sleepqueue != NULL) {
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MPASS(!TD_ON_SLEEPQ(td));
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mtx_unlock_spin(&sc->sc_lock);
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mtx_lock_spin(&sched_lock);
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return;
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}
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/*
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* Otherwise, actually go to sleep.
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*/
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mtx_lock_spin(&sched_lock);
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mtx_unlock_spin(&sc->sc_lock);
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sched_sleep(td);
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TD_SET_SLEEPING(td);
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mi_switch(SW_VOL);
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KASSERT(TD_IS_RUNNING(td), ("running but not TDS_RUNNING"));
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CTR3(KTR_PROC, "sleepq resume: thread %p (pid %ld, %s)",
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(void *)td, (long)td->td_proc->p_pid, (void *)td->td_proc->p_comm);
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}
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/*
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* Check to see if we timed out.
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*/
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static int
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sleepq_check_timeout(void)
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{
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struct thread *td;
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mtx_assert(&sched_lock, MA_OWNED);
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td = curthread;
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/*
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* If TDF_TIMEOUT is set, we timed out.
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*/
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if (td->td_flags & TDF_TIMEOUT) {
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td->td_flags &= ~TDF_TIMEOUT;
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return (EWOULDBLOCK);
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}
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/*
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* If TDF_TIMOFAIL is set, the timeout ran after we had
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* already been woken up.
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*/
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if (td->td_flags & TDF_TIMOFAIL)
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td->td_flags &= ~TDF_TIMOFAIL;
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/*
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* If callout_stop() fails, then the timeout is running on
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* another CPU, so synchronize with it to avoid having it
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* accidentally wake up a subsequent sleep.
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*/
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else if (callout_stop(&td->td_slpcallout) == 0) {
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td->td_flags |= TDF_TIMEOUT;
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TD_SET_SLEEPING(td);
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mi_switch(SW_INVOL);
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}
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return (0);
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}
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|
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/*
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* Check to see if we were awoken by a signal.
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*/
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static int
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sleepq_check_signals(void)
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{
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struct thread *td;
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mtx_assert(&sched_lock, MA_OWNED);
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td = curthread;
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/* We are no longer in an interruptible sleep. */
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td->td_flags &= ~TDF_SINTR;
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if (td->td_flags & TDF_INTERRUPT)
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return (td->td_intrval);
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return (0);
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}
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|
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/*
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* If we were in an interruptible sleep and we weren't interrupted and
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* didn't timeout, check to see if there are any pending signals and
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* which return value we should use if so. The return value from an
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* earlier call to sleepq_catch_signals() should be passed in as the
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* argument.
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*/
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int
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sleepq_calc_signal_retval(int sig)
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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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td = curthread;
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p = td->td_proc;
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PROC_LOCK(p);
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mtx_lock(&p->p_sigacts->ps_mtx);
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/* XXX: Should we always be calling cursig()? */
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if (sig == 0)
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sig = cursig(td);
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if (sig != 0) {
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if (SIGISMEMBER(p->p_sigacts->ps_sigintr, sig))
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rval = EINTR;
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else
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rval = ERESTART;
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} else
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rval = 0;
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mtx_unlock(&p->p_sigacts->ps_mtx);
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PROC_UNLOCK(p);
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return (rval);
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}
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|
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/*
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* Block the current thread until it is awakened from its sleep queue.
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*/
|
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void
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sleepq_wait(void *wchan)
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{
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sleepq_switch(wchan);
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mtx_unlock_spin(&sched_lock);
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}
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|
|
/*
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* Block the current thread until it is awakened from its sleep queue
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* or it is interrupted by a signal.
|
|
*/
|
|
int
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sleepq_wait_sig(void *wchan)
|
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{
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int rval;
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sleepq_switch(wchan);
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rval = sleepq_check_signals();
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mtx_unlock_spin(&sched_lock);
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|
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.
|
|
*/
|
|
static void
|
|
sleepq_remove_thread(struct sleepqueue *sq, struct thread *td)
|
|
{
|
|
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);
|
|
|
|
mtx_lock_spin(&sched_lock);
|
|
td->td_wmesg = NULL;
|
|
td->td_wchan = NULL;
|
|
mtx_unlock_spin(&sched_lock);
|
|
}
|
|
|
|
/*
|
|
* Resumes a thread that was asleep on a queue.
|
|
*/
|
|
static void
|
|
sleepq_resume_thread(struct thread *td, int pri)
|
|
{
|
|
|
|
/*
|
|
* 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.
|
|
*/
|
|
mtx_lock_spin(&sched_lock);
|
|
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)
|
|
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;
|
|
struct thread *td;
|
|
|
|
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);
|
|
|
|
/* Remove first thread from queue and awaken it. */
|
|
td = TAILQ_FIRST(&sq->sq_blocked);
|
|
sleepq_remove_thread(sq, td);
|
|
sleepq_release(wchan);
|
|
sleepq_resume_thread(td, pri);
|
|
}
|
|
|
|
/*
|
|
* Resume all threads sleeping on a specified wait channel.
|
|
*/
|
|
void
|
|
sleepq_broadcast(void *wchan, int flags, int pri)
|
|
{
|
|
TAILQ_HEAD(, thread) list;
|
|
struct sleepqueue *sq;
|
|
struct thread *td;
|
|
|
|
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);
|
|
|
|
/* Move blocked threads from the sleep queue to a temporary list. */
|
|
TAILQ_INIT(&list);
|
|
while (!TAILQ_EMPTY(&sq->sq_blocked)) {
|
|
td = TAILQ_FIRST(&sq->sq_blocked);
|
|
sleepq_remove_thread(sq, td);
|
|
TAILQ_INSERT_TAIL(&list, td, td_slpq);
|
|
}
|
|
sleepq_release(wchan);
|
|
|
|
/* Resume all the threads on the temporary list. */
|
|
while (!TAILQ_EMPTY(&list)) {
|
|
td = TAILQ_FIRST(&list);
|
|
TAILQ_REMOVE(&list, td, td_slpq);
|
|
sleepq_resume_thread(td, pri);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* 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);
|
|
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;
|
|
mtx_unlock_spin(&sched_lock);
|
|
sleepq_remove_thread(sq, td);
|
|
sleepq_release(wchan);
|
|
sleepq_resume_thread(td, -1);
|
|
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);
|
|
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_remove_thread(sq, td);
|
|
sleepq_release(wchan);
|
|
sleepq_resume_thread(td, -1);
|
|
}
|
|
|
|
/*
|
|
* 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)
|
|
{
|
|
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 %ld, %s)",
|
|
(void *)td, (long)td->td_proc->p_pid, (void *)td->td_proc->p_comm);
|
|
wchan = td->td_wchan;
|
|
mtx_unlock_spin(&sched_lock);
|
|
sleepq_remove(td, wchan);
|
|
mtx_lock_spin(&sched_lock);
|
|
}
|