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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
109 lines
5 KiB
C
109 lines
5 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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* $FreeBSD$
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*/
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#ifndef _SYS_SLEEPQUEUE_H_
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#define _SYS_SLEEPQUEUE_H_
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/*
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* Sleep queue interface. Sleep/wakeup and condition variables use a sleep
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* queue for the queue of threads blocked on a sleep channel.
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*
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* A thread calls sleepq_lock() to lock the sleep queue chain associated
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* with a given wait channel. A thread can then call call sleepq_add() to
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* add themself onto a sleep queue and call one of the sleepq_wait()
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* functions to actually go to sleep. If a thread needs to abort a sleep
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* operation it should call sleepq_release() to unlock the associated sleep
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* queue chain lock. If the thread also needs to remove itself from a queue
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* it just enqueued itself on, it can use sleepq_remove() instead.
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*
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* If the thread only wishes to sleep for a limited amount of time, it can
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* call sleepq_set_timeout() after sleepq_add() to setup a timeout. It
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* should then use one of the sleepq_timedwait() functions to block.
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*
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* If the thread wants to the sleep to be interruptible by signals, it can
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* call sleepq_catch_signals() after sleepq_add(). It should then use
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* one of the sleepq_wait_sig() functions to block. After the thread has
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* been resumed, it should call sleepq_calc_signal_retval() to determine
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* if it should return EINTR or ERESTART passing in the value returned from
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* the earlier call to sleepq_catch_signals().
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*
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* A thread is normally resumed from a sleep queue by either the
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* sleepq_signal() or sleepq_broadcast() functions. Sleepq_signal() wakes
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* the thread with the highest priority that is sleeping on the specified
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* wait channel. Sleepq_broadcast() wakes all threads that are sleeping
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* on the specified wait channel. A thread sleeping in an interruptible
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* sleep can be interrupted by calling sleepq_abort(). A thread can also
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* be removed from a specified sleep queue using the sleepq_remove()
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* function. Note that the sleep queue chain must first be locked via
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* sleepq_lock() when calling sleepq_signal() and sleepq_broadcast().
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*
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* Each thread allocates a sleep queue at thread creation via sleepq_alloc()
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* and releases it at thread destruction via sleepq_free(). Note that
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* a sleep queue is not tied to a specific thread and that the sleep queue
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* released at thread destruction may not be the same sleep queue that the
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* thread allocated when it was created.
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*
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* XXX: Some other parts of the kernel such as ithread sleeping may end up
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* using this interface as well (death to TDI_IWAIT!)
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*/
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struct mtx;
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struct sleepqueue;
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struct thread;
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#ifdef _KERNEL
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#define SLEEPQ_TYPE 0x0ff /* Mask of sleep queue types. */
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#define SLEEPQ_MSLEEP 0x00 /* Used by msleep/wakeup. */
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#define SLEEPQ_CONDVAR 0x01 /* Used for a cv. */
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#define SLEEPQ_INTERRUPTIBLE 0x100 /* Sleep is interruptible. */
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void init_sleepqueues(void);
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void sleepq_abort(struct thread *td);
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void sleepq_add(void *, struct mtx *, const char *, int);
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struct sleepqueue *sleepq_alloc(void);
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void sleepq_broadcast(void *, int, int);
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int sleepq_calc_signal_retval(int sig);
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int sleepq_catch_signals(void *wchan);
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void sleepq_free(struct sleepqueue *);
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void sleepq_lock(void *);
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struct sleepqueue *sleepq_lookup(void *);
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void sleepq_release(void *);
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void sleepq_remove(struct thread *, void *);
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void sleepq_signal(void *, int, int);
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void sleepq_set_timeout(void *wchan, int timo);
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int sleepq_timedwait(void *wchan);
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int sleepq_timedwait_sig(void *wchan, int signal_caught);
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void sleepq_wait(void *);
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int sleepq_wait_sig(void *wchan);
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#endif /* _KERNEL */
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#endif /* !_SYS_SLEEPQUEUE_H_ */
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