WebSVN – HelenOS – Blame – /trunk/kernel/generic/src/synch/waitq.c

Rev	Author	Line No.	Line
1	jermar	1	/*
		2	* Copyright (C) 2001-2004 Jakub Jermar
		3	* All rights reserved.
		4	*
		5	* Redistribution and use in source and binary forms, with or without
		6	* modification, are permitted provided that the following conditions
		7	* are met:
		8	*
		9	* - Redistributions of source code must retain the above copyright
		10	* notice, this list of conditions and the following disclaimer.
		11	* - Redistributions in binary form must reproduce the above copyright
		12	* notice, this list of conditions and the following disclaimer in the
		13	* documentation and/or other materials provided with the distribution.
		14	* - The name of the author may not be used to endorse or promote products
		15	* derived from this software without specific prior written permission.
		16	*
		17	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
		18	* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
		19	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
		20	* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
		21	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
		22	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
		23	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
		24	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
		25	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
		26	* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
		27	*/
		28
		29	#include <context.h>
		30	#include <proc/thread.h>
		31
		32	#include <synch/synch.h>
		33	#include <synch/waitq.h>
		34	#include <synch/spinlock.h>
		35
		36	#include <arch/asm.h>
		37	#include <arch/types.h>
		38	#include <arch.h>
		39
		40	#include <list.h>
		41
		42	#include <time/timeout.h>
		43
		44	void waitq_initialize(waitq_t *wq)
		45	{
		46	spinlock_initialize(&wq->lock);
		47	list_initialize(&wq->head);
		48	wq->missed_wakeups = 0;
		49	}
		50
		51	/*
		52	* Called with interrupts disabled from clock() when sleep_timeout
		53	* timeouts. This function is not allowed to enable interrupts.
		54	*
		55	* It is supposed to try to remove 'its' thread from the waitqueue; it
		56	* can eventually fail to achieve this goal when these two events
		57	* overlap; in that case it behaves just as though there was no
		58	* timeout at all
		59	*/
		60	void waitq_interrupted_sleep(void *data)
		61	{
		62	thread_t t = (thread_t ) data;
		63	waitq_t *wq;
		64	int do_wakeup = 0;
		65
		66	spinlock_lock(&threads_lock);
		67	if (!list_member(&t->threads_link, &threads_head))
		68	goto out;
		69
		70	grab_locks:
		71	spinlock_lock(&t->lock);
		72	if (wq = t->sleep_queue) {
		73	if (!spinlock_trylock(&wq->lock)) {
		74	spinlock_unlock(&t->lock);
		75	goto grab_locks; /* avoid deadlock */
		76	}
		77
		78	list_remove(&t->wq_link);
		79	t->saved_context = t->sleep_timeout_context;
		80	do_wakeup = 1;
		81
		82	spinlock_unlock(&wq->lock);
		83	t->sleep_queue = NULL;
		84	}
		85
		86	t->timeout_pending = 0;
		87	spinlock_unlock(&t->lock);
		88
		89	if (do_wakeup) thread_ready(t);
		90
		91	out:
		92	spinlock_unlock(&threads_lock);
		93	}
		94
		95	/*
		96	* This is a sleep implementation which allows itself to be
		97	* interrupted from the sleep, restoring a failover context.
		98	*
		99	* This function is really basic in that other functions as waitq_sleep()
		100	* and all the *_timeout() functions use it.
		101	*
		102	* The third argument controls whether only a conditional sleep
		103	* (non-blocking sleep) is called for when the second argument is 0.
		104	*
		105	* usec \| nonblocking \| what happens if there is no missed_wakeup
		106	* -----+-------------+--------------------------------------------
		107	* 0 \| 0 \| blocks without timeout until wakeup
		108	* 0 \| <> 0 \| immediately returns ESYNCH_WOULD_BLOCK
		109	* > 0 \| x \| blocks with timeout until timeout or wakeup
		110	*
		111	* return values:
		112	* ESYNCH_WOULD_BLOCK
		113	* ESYNCH_TIMEOUT
		114	* ESYNCH_OK_ATOMIC
		115	* ESYNCH_OK_BLOCKED
		116	*/
		117	int waitq_sleep_timeout(waitq_t *wq, __u32 usec, int nonblocking)
		118	{
		119	volatile pri_t pri; /* must be live after context_restore() */
		120
		121
		122	restart:
		123	pri = cpu_priority_high();
		124
		125	/*
		126	* Busy waiting for a delayed timeout.
		127	* This is an important fix for the race condition between
		128	* a delayed timeout and a next call to waitq_sleep_timeout().
		129	* Simply, the thread is not allowed to go to sleep if
		130	* there are timeouts in progress.
		131	*/
15	jermar	132	spinlock_lock(&THREAD->lock);
		133	if (THREAD->timeout_pending) {
		134	spinlock_unlock(&THREAD->lock);
1	jermar	135	cpu_priority_restore(pri);
		136	goto restart;
		137	}
15	jermar	138	spinlock_unlock(&THREAD->lock);
1	jermar	139
		140	spinlock_lock(&wq->lock);
		141
		142	/* checks whether to go to sleep at all */
		143	if (wq->missed_wakeups) {
		144	wq->missed_wakeups--;
		145	spinlock_unlock(&wq->lock);
		146	cpu_priority_restore(pri);
		147	return ESYNCH_OK_ATOMIC;
		148	}
		149	else {
		150	if (nonblocking && (usec == 0)) {
		151	/* return immediatelly instead of going to sleep */
		152	spinlock_unlock(&wq->lock);
		153	cpu_priority_restore(pri);
		154	return ESYNCH_WOULD_BLOCK;
		155	}
		156	}
		157
		158
		159	/*
		160	* Now we are firmly decided to go to sleep.
		161	*/
15	jermar	162	spinlock_lock(&THREAD->lock);
1	jermar	163	if (usec) {
		164	/* We use the timeout variant. */
15	jermar	165	if (!context_save(&THREAD->sleep_timeout_context)) {
1	jermar	166	/*
		167	* Short emulation of scheduler() return code.
		168	*/
15	jermar	169	spinlock_unlock(&THREAD->lock);
1	jermar	170	cpu_priority_restore(pri);
		171	return ESYNCH_TIMEOUT;
		172	}
15	jermar	173	THREAD->timeout_pending = 1;
		174	timeout_register(&THREAD->sleep_timeout, (__u64) usec, waitq_interrupted_sleep, THREAD);
1	jermar	175	}
		176
15	jermar	177	list_append(&THREAD->wq_link, &wq->head);
1	jermar	178
		179	/*
		180	* Suspend execution.
		181	*/
15	jermar	182	THREAD->state = Sleeping;
		183	THREAD->sleep_queue = wq;
1	jermar	184
15	jermar	185	spinlock_unlock(&THREAD->lock);
1	jermar	186
		187	scheduler(); /* wq->lock is released in scheduler_separated_stack() */
		188	cpu_priority_restore(pri);
		189
		190	return ESYNCH_OK_BLOCKED;
		191	}
		192
		193
		194	/*
		195	* This is the SMP- and IRQ-safe wrapper meant for general use.
		196	*/
		197	/*
		198	* Besides its 'normal' wakeup operation, it attempts to unregister possible timeout.
		199	*/
		200	void waitq_wakeup(waitq_t *wq, int all)
		201	{
		202	pri_t pri;
		203
		204	pri = cpu_priority_high();
		205	spinlock_lock(&wq->lock);
		206
		207	_waitq_wakeup_unsafe(wq, all);
		208
		209	spinlock_unlock(&wq->lock);
		210	cpu_priority_restore(pri);
		211	}
		212
		213	/*
		214	* This is the internal SMP- and IRQ-unsafe version of waitq_wakeup.
		215	* It assumes wq->lock is already locked.
		216	*/
		217	void _waitq_wakeup_unsafe(waitq_t *wq, int all)
		218	{
		219	thread_t *t;
		220
		221	loop:
		222	if (list_empty(&wq->head)) {
		223	wq->missed_wakeups++;
		224	if (all) wq->missed_wakeups = 0;
		225	return;
		226	}
		227
		228	t = list_get_instance(wq->head.next, thread_t, wq_link);
		229
		230	list_remove(&t->wq_link);
		231	spinlock_lock(&t->lock);
		232	if (t->timeout_pending && timeout_unregister(&t->sleep_timeout))
		233	t->timeout_pending = 0;
		234	t->sleep_queue = NULL;
		235	spinlock_unlock(&t->lock);
		236
		237	thread_ready(t);
		238
		239	if (all) goto loop;
		240	}

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(root)/trunk/kernel/generic/src/synch/waitq.c @ 2145 – Rev 15