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


/*
 * Copyright (c) 2001-2004 Jakub Jermar
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
 
/** @addtogroup sync
 * @{
 */
 
/**
 * @file
 * @brief   Wait queue.
 *
 * Wait queue is the basic synchronization primitive upon which all
 * other synchronization primitives build.
 *
 * It allows threads to wait for an event in first-come, first-served
 * fashion. Conditional operation as well as timeouts and interruptions
 * are supported.
 */
 
#include <synch/waitq.h>
#include <synch/synch.h>
#include <synch/spinlock.h>
#include <proc/thread.h>
#include <proc/scheduler.h>
#include <arch/asm.h>
#include <arch/types.h>
 
#include <time/timeout.h>
#include <arch.h>
#include <context.h>
#include <adt/list.h>
 
static void waitq_timeouted_sleep(void *data);
 
/** Initialize wait queue
 *
 * Initialize wait queue.
 *
 * @param wq Pointer to wait queue to be initialized.
 */
void waitq_initialize(waitq_t *wq)
{
    spinlock_initialize(&wq->lock, "waitq_lock");
    list_initialize(&wq->head);
    wq->missed_wakeups = 0;
}
 
/** Handle timeout during waitq_sleep_timeout() call
 *
 * This routine is called when waitq_sleep_timeout() timeouts.
 * Interrupts are disabled.
 *
 * It is supposed to try to remove 'its' thread from the wait queue;
 * it can eventually fail to achieve this goal when these two events
 * overlap. In that case it behaves just as though there was no
 * timeout at all.
 *
 * @param data Pointer to the thread that called waitq_sleep_timeout().
 */
void waitq_timeouted_sleep(void *data)
{
    thread_t *t = (thread_t *) data;
    waitq_t *wq;
    bool do_wakeup = false;
 
    spinlock_lock(&threads_lock);
    if (!thread_exists(t))
        goto out;
 
grab_locks:
    spinlock_lock(&t->lock);
    if ((wq = t->sleep_queue)) {        /* assignment */
        if (!spinlock_trylock(&wq->lock)) {
            spinlock_unlock(&t->lock);
            goto grab_locks;    /* avoid deadlock */
        }
 
        list_remove(&t->wq_link);
        t->saved_context = t->sleep_timeout_context;
        do_wakeup = true;
        t->sleep_queue = NULL;
        spinlock_unlock(&wq->lock);
    }
   
    t->timeout_pending = false;
    spinlock_unlock(&t->lock);
   
    if (do_wakeup)
        thread_ready(t);
 
out:
    spinlock_unlock(&threads_lock);
}
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
/** Sleep until either wakeup, timeout or interruption occurs
 *
 * This is a sleep implementation which allows itself to time out or to be
 * interrupted from the sleep, restoring a failover context.
 *
 * Sleepers are organised in a FIFO fashion in a structure called wait queue.
 *
 * This function is really basic in that other functions as waitq_sleep()
 * and all the *_timeout() functions use it.
 *
 * @param wq Pointer to wait queue.
 * @param usec Timeout in microseconds.
 * @param flags Specify mode of the sleep.
 *
 * The sleep can be interrupted only if the
 * SYNCH_FLAGS_INTERRUPTIBLE bit is specified in flags.
 *
 * If usec is greater than zero, regardless of the value of the
 * SYNCH_FLAGS_NON_BLOCKING bit in flags, the call will not return until either
 * timeout, interruption or wakeup comes.
 *
 * If usec is zero and the SYNCH_FLAGS_NON_BLOCKING bit is not set in flags,
 * the call will not return until wakeup or interruption comes.
 *
 * If usec is zero and the SYNCH_FLAGS_NON_BLOCKING bit is set in flags, the
 * call will immediately return, reporting either success or failure.
 *
 * @return One of: ESYNCH_WOULD_BLOCK, ESYNCH_TIMEOUT, ESYNCH_INTERRUPTED,
 * ESYNCH_OK_ATOMIC, ESYNCH_OK_BLOCKED.
 *
 * @li ESYNCH_WOULD_BLOCK means that the sleep failed because at the time of the
 * call there was no pending wakeup.
 *
 * @li ESYNCH_TIMEOUT means that the sleep timed out.
 *
 * @li ESYNCH_INTERRUPTED means that somebody interrupted the sleeping thread.
 *
 * @li ESYNCH_OK_ATOMIC means that the sleep succeeded and that there was
 * a pending wakeup at the time of the call. The caller was not put
 * asleep at all.
 *
 * @li ESYNCH_OK_BLOCKED means that the sleep succeeded; the full sleep was
 * attempted.
 */
int waitq_sleep_timeout(waitq_t *wq, uint32_t usec, int flags)
{
    ipl_t ipl;
    int rc;
   
    ipl = waitq_sleep_prepare(wq);
    rc = waitq_sleep_timeout_unsafe(wq, usec, flags);
    waitq_sleep_finish(wq, rc, ipl);
    return rc;
}
 
/** Prepare to sleep in a waitq.
 *
 * This function will return holding the lock of the wait queue
 * and interrupts disabled.
 *
 * @param wq Wait queue.
 *
 * @return Interrupt level as it existed on entry to this function.
 */
ipl_t waitq_sleep_prepare(waitq_t *wq)
{
    ipl_t ipl;
   
restart:
    ipl = interrupts_disable();
 
    if (THREAD) {   /* needed during system initiailzation */
        /*
         * Busy waiting for a delayed timeout.
         * This is an important fix for the race condition between
         * a delayed timeout and a next call to waitq_sleep_timeout().
         * Simply, the thread is not allowed to go to sleep if
         * there are timeouts in progress.
         */
        spinlock_lock(&THREAD->lock);
        if (THREAD->timeout_pending) {
            spinlock_unlock(&THREAD->lock);
            interrupts_restore(ipl);
            goto restart;
        }
        spinlock_unlock(&THREAD->lock);
    }
                                                   
    spinlock_lock(&wq->lock);
    return ipl;
}
 
/** Finish waiting in a wait queue.
 *
 * This function restores interrupts to the state that existed prior
 * to the call to waitq_sleep_prepare(). If necessary, the wait queue
 * lock is released.
 *
 * @param wq Wait queue.
 * @param rc Return code of waitq_sleep_timeout_unsafe().
 * @param ipl Interrupt level returned by waitq_sleep_prepare().
 */
void waitq_sleep_finish(waitq_t *wq, int rc, ipl_t ipl)
{
    switch (rc) {
    case ESYNCH_WOULD_BLOCK:
    case ESYNCH_OK_ATOMIC:
        spinlock_unlock(&wq->lock);
        break;
    default:
        break;
    }
    interrupts_restore(ipl);
}
 
/** Internal implementation of waitq_sleep_timeout().
 *
 * This function implements logic of sleeping in a wait queue.
 * This call must be preceeded by a call to waitq_sleep_prepare()
 * and followed by a call to waitq_slee_finish().
 *
 * @param wq See waitq_sleep_timeout().
 * @param usec See waitq_sleep_timeout().
 * @param flags See waitq_sleep_timeout().
 *
 * @return See waitq_sleep_timeout().
 */
int waitq_sleep_timeout_unsafe(waitq_t *wq, uint32_t usec, int flags)
{
    /* checks whether to go to sleep at all */
    if (wq->missed_wakeups) {
        wq->missed_wakeups--;
        return ESYNCH_OK_ATOMIC;
    }
    else {
        if ((flags & SYNCH_FLAGS_NON_BLOCKING) && (usec == 0)) {
            /* return immediatelly instead of going to sleep */
            return ESYNCH_WOULD_BLOCK;
        }
    }
   
    /*
     * Now we are firmly decided to go to sleep.
     */
    spinlock_lock(&THREAD->lock);
 
    if (flags & SYNCH_FLAGS_INTERRUPTIBLE) {
 
        /*
         * If the thread was already interrupted,
         * don't go to sleep at all.
         */
        if (THREAD->interrupted) {
            spinlock_unlock(&THREAD->lock);
            spinlock_unlock(&wq->lock);
            return ESYNCH_INTERRUPTED;
        }
 
        /*
         * Set context that will be restored if the sleep
         * of this thread is ever interrupted.
         */
        THREAD->sleep_interruptible = true;
        if (!context_save(&THREAD->sleep_interruption_context)) {
            /* Short emulation of scheduler() return code. */
            spinlock_unlock(&THREAD->lock);
            return ESYNCH_INTERRUPTED;
        }
 
    } else {
        THREAD->sleep_interruptible = false;
    }
 
    if (usec) {
        /* We use the timeout variant. */
        if (!context_save(&THREAD->sleep_timeout_context)) {
            /* Short emulation of scheduler() return code. */
            spinlock_unlock(&THREAD->lock);
            return ESYNCH_TIMEOUT;
        }
        THREAD->timeout_pending = true;
        timeout_register(&THREAD->sleep_timeout, (uint64_t) usec,
            waitq_timeouted_sleep, THREAD);
    }
 
    list_append(&THREAD->wq_link, &wq->head);
 
    /*
     * Suspend execution.
     */
    THREAD->state = Sleeping;
    THREAD->sleep_queue = wq;
 
    spinlock_unlock(&THREAD->lock);
 
    /* wq->lock is released in scheduler_separated_stack() */
    scheduler();
   
    return ESYNCH_OK_BLOCKED;
}
 
 
/** Wake up first thread sleeping in a wait queue
 *
 * Wake up first thread sleeping in a wait queue. This is the SMP- and IRQ-safe
 * wrapper meant for general use.
 *
 * Besides its 'normal' wakeup operation, it attempts to unregister possible
 * timeout.
 *
 * @param wq Pointer to wait queue.
 * @param all If this is non-zero, all sleeping threads will be woken up and
 *  missed count will be zeroed.
 */
void waitq_wakeup(waitq_t *wq, bool all)
{
    ipl_t ipl;
 
    ipl = interrupts_disable();
    spinlock_lock(&wq->lock);
 
    _waitq_wakeup_unsafe(wq, all);
 
    spinlock_unlock(&wq->lock);
    interrupts_restore(ipl);   
}
 
/** Internal SMP- and IRQ-unsafe version of waitq_wakeup()
 *
 * This is the internal SMP- and IRQ-unsafe version of waitq_wakeup(). It
 * assumes wq->lock is already locked and interrupts are already disabled.
 *
 * @param wq Pointer to wait queue.
 * @param all If this is non-zero, all sleeping threads will be woken up and
 *  missed count will be zeroed.
 */
void _waitq_wakeup_unsafe(waitq_t *wq, bool all)
{
    thread_t *t;
 
loop:  
    if (list_empty(&wq->head)) {
        wq->missed_wakeups++;
        if (all)
            wq->missed_wakeups = 0;
        return;
    }
 
    t = list_get_instance(wq->head.next, thread_t, wq_link);
   
    /*
     * Lock the thread prior to removing it from the wq.
     * This is not necessary because of mutual exclusion
     * (the link belongs to the wait queue), but because
     * of synchronization with waitq_timeouted_sleep()
     * and thread_interrupt_sleep().
     *
     * In order for these two functions to work, the following
     * invariant must hold:
     *
     * t->sleep_queue != NULL <=> t sleeps in a wait queue
     *
     * For an observer who locks the thread, the invariant
     * holds only when the lock is held prior to removing
     * it from the wait queue.
     */
    spinlock_lock(&t->lock);
    list_remove(&t->wq_link);
   
    if (t->timeout_pending && timeout_unregister(&t->sleep_timeout))
        t->timeout_pending = false;
    t->sleep_queue = NULL;
    spinlock_unlock(&t->lock);
 
    thread_ready(t);
 
    if (all)
        goto loop;
}
 
/** @}
 */
 

Rev 2087	Rev 2089
1	/*	1	/*
2	* Copyright (c) 2001-2004 Jakub Jermar	2	* Copyright (c) 2001-2004 Jakub Jermar
3	* All rights reserved.	3	* All rights reserved.
4	*	4	*
5	* Redistribution and use in source and binary forms, with or without	5	* Redistribution and use in source and binary forms, with or without
6	* modification, are permitted provided that the following conditions	6	* modification, are permitted provided that the following conditions
7	* are met:	7	* are met:
8	*	8	*
9	* - Redistributions of source code must retain the above copyright	9	* - Redistributions of source code must retain the above copyright
10	* notice, this list of conditions and the following disclaimer.	10	* notice, this list of conditions and the following disclaimer.
11	* - Redistributions in binary form must reproduce the above copyright	11	* - Redistributions in binary form must reproduce the above copyright
12	* notice, this list of conditions and the following disclaimer in the	12	* notice, this list of conditions and the following disclaimer in the
13	* documentation and/or other materials provided with the distribution.	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	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.	15	* derived from this software without specific prior written permission.
16	*	16	*
17	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR	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	18	* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.	19	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20	* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,	20	* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT	21	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,	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	23	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT	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	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.	26	* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27	*/	27	*/
28		28
29	/** @addtogroup sync	29	/** @addtogroup sync
30	* @{	30	* @{
31	*/	31	*/
32		32
33	/**	33	/**
34	* @file	34	* @file
35	* @brief Wait queue.	35	* @brief Wait queue.
36	*	36	*
37	* Wait queue is the basic synchronization primitive upon which all	37	* Wait queue is the basic synchronization primitive upon which all
38	* other synchronization primitives build.	38	* other synchronization primitives build.
39	*	39	*
40	* It allows threads to wait for an event in first-come, first-served	40	* It allows threads to wait for an event in first-come, first-served
41	* fashion. Conditional operation as well as timeouts and interruptions	41	* fashion. Conditional operation as well as timeouts and interruptions
42	* are supported.	42	* are supported.
43	*/	43	*/
44		44
45	#include <synch/waitq.h>	45	#include <synch/waitq.h>
46	#include <synch/synch.h>	46	#include <synch/synch.h>
47	#include <synch/spinlock.h>	47	#include <synch/spinlock.h>
48	#include <proc/thread.h>	48	#include <proc/thread.h>
49	#include <proc/scheduler.h>	49	#include <proc/scheduler.h>
50	#include <arch/asm.h>	50	#include <arch/asm.h>
51	#include <arch/types.h>	51	#include <arch/types.h>
52	#include <typedefs.h>	-
53	#include <time/timeout.h>	52	#include <time/timeout.h>
54	#include <arch.h>	53	#include <arch.h>
55	#include <context.h>	54	#include <context.h>
56	#include <adt/list.h>	55	#include <adt/list.h>
57		56
58	static void waitq_timeouted_sleep(void *data);	57	static void waitq_timeouted_sleep(void *data);
59		58
60	/** Initialize wait queue	59	/** Initialize wait queue
61	*	60	*
62	* Initialize wait queue.	61	* Initialize wait queue.
63	*	62	*
64	* @param wq Pointer to wait queue to be initialized.	63	* @param wq Pointer to wait queue to be initialized.
65	*/	64	*/
66	void waitq_initialize(waitq_t *wq)	65	void waitq_initialize(waitq_t *wq)
67	{	66	{
68	spinlock_initialize(&wq->lock, "waitq_lock");	67	spinlock_initialize(&wq->lock, "waitq_lock");
69	list_initialize(&wq->head);	68	list_initialize(&wq->head);
70	wq->missed_wakeups = 0;	69	wq->missed_wakeups = 0;
71	}	70	}
72		71
73	/** Handle timeout during waitq_sleep_timeout() call	72	/** Handle timeout during waitq_sleep_timeout() call
74	*	73	*
75	* This routine is called when waitq_sleep_timeout() timeouts.	74	* This routine is called when waitq_sleep_timeout() timeouts.
76	* Interrupts are disabled.	75	* Interrupts are disabled.
77	*	76	*
78	* It is supposed to try to remove 'its' thread from the wait queue;	77	* It is supposed to try to remove 'its' thread from the wait queue;
79	* it can eventually fail to achieve this goal when these two events	78	* it can eventually fail to achieve this goal when these two events
80	* overlap. In that case it behaves just as though there was no	79	* overlap. In that case it behaves just as though there was no
81	* timeout at all.	80	* timeout at all.
82	*	81	*
83	* @param data Pointer to the thread that called waitq_sleep_timeout().	82	* @param data Pointer to the thread that called waitq_sleep_timeout().
84	*/	83	*/
85	void waitq_timeouted_sleep(void *data)	84	void waitq_timeouted_sleep(void *data)
86	{	85	{
87	thread_t t = (thread_t ) data;	86	thread_t t = (thread_t ) data;
88	waitq_t *wq;	87	waitq_t *wq;
89	bool do_wakeup = false;	88	bool do_wakeup = false;
90		89
91	spinlock_lock(&threads_lock);	90	spinlock_lock(&threads_lock);
92	if (!thread_exists(t))	91	if (!thread_exists(t))
93	goto out;	92	goto out;
94		93
95	grab_locks:	94	grab_locks:
96	spinlock_lock(&t->lock);	95	spinlock_lock(&t->lock);
97	if ((wq = t->sleep_queue)) { /* assignment */	96	if ((wq = t->sleep_queue)) { /* assignment */
98	if (!spinlock_trylock(&wq->lock)) {	97	if (!spinlock_trylock(&wq->lock)) {
99	spinlock_unlock(&t->lock);	98	spinlock_unlock(&t->lock);
100	goto grab_locks; /* avoid deadlock */	99	goto grab_locks; /* avoid deadlock */
101	}	100	}
102		101
103	list_remove(&t->wq_link);	102	list_remove(&t->wq_link);
104	t->saved_context = t->sleep_timeout_context;	103	t->saved_context = t->sleep_timeout_context;
105	do_wakeup = true;	104	do_wakeup = true;
106	t->sleep_queue = NULL;	105	t->sleep_queue = NULL;
107	spinlock_unlock(&wq->lock);	106	spinlock_unlock(&wq->lock);
108	}	107	}
109		108
110	t->timeout_pending = false;	109	t->timeout_pending = false;
111	spinlock_unlock(&t->lock);	110	spinlock_unlock(&t->lock);
112		111
113	if (do_wakeup)	112	if (do_wakeup)
114	thread_ready(t);	113	thread_ready(t);
115		114
116	out:	115	out:
117	spinlock_unlock(&threads_lock);	116	spinlock_unlock(&threads_lock);
118	}	117	}
119		118
120	/** Interrupt sleeping thread.	-
121	*	-
122	* This routine attempts to interrupt a thread from its sleep in a waitqueue.	-
123	* If the thread is not found sleeping, no action is taken.	-
124	*	-
125	* @param t Thread to be interrupted.	-
126	*/	-
127	void waitq_interrupt_sleep(thread_t *t)	-
128	{	-
129	waitq_t *wq;	-
130	bool do_wakeup = false;	-
131	ipl_t ipl;	-
132		-
133	ipl = interrupts_disable();	-
134	spinlock_lock(&threads_lock);	-
135	if (!thread_exists(t))	-
136	goto out;	-
137		-
138	grab_locks:	-
139	spinlock_lock(&t->lock);	-
140	if ((wq = t->sleep_queue)) { /* assignment */	-
141	if (!(t->sleep_interruptible)) {	-
142	/*	-
143	* The sleep cannot be interrupted.	-
144	*/	-
145	spinlock_unlock(&t->lock);	-
146	goto out;	-
147	}	-
148		-
149	if (!spinlock_trylock(&wq->lock)) {	-
150	spinlock_unlock(&t->lock);	-
151	goto grab_locks; /* avoid deadlock */	-
152	}	-
153		-
154	if (t->timeout_pending && timeout_unregister(&t->sleep_timeout))	-
155	t->timeout_pending = false;	-
156		-
157	list_remove(&t->wq_link);	-
158	t->saved_context = t->sleep_interruption_context;	-
159	do_wakeup = true;	-
160	t->sleep_queue = NULL;	-
161	spinlock_unlock(&wq->lock);	-
162	}	-
163	spinlock_unlock(&t->lock);	-
164		-
165	if (do_wakeup)	-
166	thread_ready(t);	-
167		-
168	out:	-
169	spinlock_unlock(&threads_lock);	-
170	interrupts_restore(ipl);	-
171	}	-
172		119
173	/** Sleep until either wakeup, timeout or interruption occurs	120	/** Sleep until either wakeup, timeout or interruption occurs
174	*	121	*
175	* This is a sleep implementation which allows itself to time out or to be	122	* This is a sleep implementation which allows itself to time out or to be
176	* interrupted from the sleep, restoring a failover context.	123	* interrupted from the sleep, restoring a failover context.
177	*	124	*
178	* Sleepers are organised in a FIFO fashion in a structure called wait queue.	125	* Sleepers are organised in a FIFO fashion in a structure called wait queue.
179	*	126	*
180	* This function is really basic in that other functions as waitq_sleep()	127	* This function is really basic in that other functions as waitq_sleep()
181	* and all the *_timeout() functions use it.	128	* and all the *_timeout() functions use it.
182	*	129	*
183	* @param wq Pointer to wait queue.	130	* @param wq Pointer to wait queue.
184	* @param usec Timeout in microseconds.	131	* @param usec Timeout in microseconds.
185	* @param flags Specify mode of the sleep.	132	* @param flags Specify mode of the sleep.
186	*	133	*
187	* The sleep can be interrupted only if the	134	* The sleep can be interrupted only if the
188	* SYNCH_FLAGS_INTERRUPTIBLE bit is specified in flags.	135	* SYNCH_FLAGS_INTERRUPTIBLE bit is specified in flags.
189	*	136	*
190	* If usec is greater than zero, regardless of the value of the	137	* If usec is greater than zero, regardless of the value of the
191	* SYNCH_FLAGS_NON_BLOCKING bit in flags, the call will not return until either	138	* SYNCH_FLAGS_NON_BLOCKING bit in flags, the call will not return until either
192	* timeout, interruption or wakeup comes.	139	* timeout, interruption or wakeup comes.
193	*	140	*
194	* If usec is zero and the SYNCH_FLAGS_NON_BLOCKING bit is not set in flags,	141	* If usec is zero and the SYNCH_FLAGS_NON_BLOCKING bit is not set in flags,
195	* the call will not return until wakeup or interruption comes.	142	* the call will not return until wakeup or interruption comes.
196	*	143	*
197	* If usec is zero and the SYNCH_FLAGS_NON_BLOCKING bit is set in flags, the	144	* If usec is zero and the SYNCH_FLAGS_NON_BLOCKING bit is set in flags, the
198	* call will immediately return, reporting either success or failure.	145	* call will immediately return, reporting either success or failure.
199	*	146	*
200	* @return One of: ESYNCH_WOULD_BLOCK, ESYNCH_TIMEOUT, ESYNCH_INTERRUPTED,	147	* @return One of: ESYNCH_WOULD_BLOCK, ESYNCH_TIMEOUT, ESYNCH_INTERRUPTED,
201	* ESYNCH_OK_ATOMIC, ESYNCH_OK_BLOCKED.	148	* ESYNCH_OK_ATOMIC, ESYNCH_OK_BLOCKED.
202	*	149	*
203	* @li ESYNCH_WOULD_BLOCK means that the sleep failed because at the time of the	150	* @li ESYNCH_WOULD_BLOCK means that the sleep failed because at the time of the
204	* call there was no pending wakeup.	151	* call there was no pending wakeup.
205	*	152	*
206	* @li ESYNCH_TIMEOUT means that the sleep timed out.	153	* @li ESYNCH_TIMEOUT means that the sleep timed out.
207	*	154	*
208	* @li ESYNCH_INTERRUPTED means that somebody interrupted the sleeping thread.	155	* @li ESYNCH_INTERRUPTED means that somebody interrupted the sleeping thread.
209	*	156	*
210	* @li ESYNCH_OK_ATOMIC means that the sleep succeeded and that there was	157	* @li ESYNCH_OK_ATOMIC means that the sleep succeeded and that there was
211	* a pending wakeup at the time of the call. The caller was not put	158	* a pending wakeup at the time of the call. The caller was not put
212	* asleep at all.	159	* asleep at all.
213	*	160	*
214	* @li ESYNCH_OK_BLOCKED means that the sleep succeeded; the full sleep was	161	* @li ESYNCH_OK_BLOCKED means that the sleep succeeded; the full sleep was
215	* attempted.	162	* attempted.
216	*/	163	*/
217	int waitq_sleep_timeout(waitq_t *wq, uint32_t usec, int flags)	164	int waitq_sleep_timeout(waitq_t *wq, uint32_t usec, int flags)
218	{	165	{
219	ipl_t ipl;	166	ipl_t ipl;
220	int rc;	167	int rc;
221		168
222	ipl = waitq_sleep_prepare(wq);	169	ipl = waitq_sleep_prepare(wq);
223	rc = waitq_sleep_timeout_unsafe(wq, usec, flags);	170	rc = waitq_sleep_timeout_unsafe(wq, usec, flags);
224	waitq_sleep_finish(wq, rc, ipl);	171	waitq_sleep_finish(wq, rc, ipl);
225	return rc;	172	return rc;
226	}	173	}
227		174
228	/** Prepare to sleep in a waitq.	175	/** Prepare to sleep in a waitq.
229	*	176	*
230	* This function will return holding the lock of the wait queue	177	* This function will return holding the lock of the wait queue
231	* and interrupts disabled.	178	* and interrupts disabled.
232	*	179	*
233	* @param wq Wait queue.	180	* @param wq Wait queue.
234	*	181	*
235	* @return Interrupt level as it existed on entry to this function.	182	* @return Interrupt level as it existed on entry to this function.
236	*/	183	*/
237	ipl_t waitq_sleep_prepare(waitq_t *wq)	184	ipl_t waitq_sleep_prepare(waitq_t *wq)
238	{	185	{
239	ipl_t ipl;	186	ipl_t ipl;
240		187
241	restart:	188	restart:
242	ipl = interrupts_disable();	189	ipl = interrupts_disable();
243		190
244	if (THREAD) { /* needed during system initiailzation */	191	if (THREAD) { /* needed during system initiailzation */
245	/*	192	/*
246	* Busy waiting for a delayed timeout.	193	* Busy waiting for a delayed timeout.
247	* This is an important fix for the race condition between	194	* This is an important fix for the race condition between
248	* a delayed timeout and a next call to waitq_sleep_timeout().	195	* a delayed timeout and a next call to waitq_sleep_timeout().
249	* Simply, the thread is not allowed to go to sleep if	196	* Simply, the thread is not allowed to go to sleep if
250	* there are timeouts in progress.	197	* there are timeouts in progress.
251	*/	198	*/
252	spinlock_lock(&THREAD->lock);	199	spinlock_lock(&THREAD->lock);
253	if (THREAD->timeout_pending) {	200	if (THREAD->timeout_pending) {
254	spinlock_unlock(&THREAD->lock);	201	spinlock_unlock(&THREAD->lock);
255	interrupts_restore(ipl);	202	interrupts_restore(ipl);
256	goto restart;	203	goto restart;
257	}	204	}
258	spinlock_unlock(&THREAD->lock);	205	spinlock_unlock(&THREAD->lock);
259	}	206	}
260		207
261	spinlock_lock(&wq->lock);	208	spinlock_lock(&wq->lock);
262	return ipl;	209	return ipl;
263	}	210	}
264		211
265	/** Finish waiting in a wait queue.	212	/** Finish waiting in a wait queue.
266	*	213	*
267	* This function restores interrupts to the state that existed prior	214	* This function restores interrupts to the state that existed prior
268	* to the call to waitq_sleep_prepare(). If necessary, the wait queue	215	* to the call to waitq_sleep_prepare(). If necessary, the wait queue
269	* lock is released.	216	* lock is released.
270	*	217	*
271	* @param wq Wait queue.	218	* @param wq Wait queue.
272	* @param rc Return code of waitq_sleep_timeout_unsafe().	219	* @param rc Return code of waitq_sleep_timeout_unsafe().
273	* @param ipl Interrupt level returned by waitq_sleep_prepare().	220	* @param ipl Interrupt level returned by waitq_sleep_prepare().
274	*/	221	*/
275	void waitq_sleep_finish(waitq_t *wq, int rc, ipl_t ipl)	222	void waitq_sleep_finish(waitq_t *wq, int rc, ipl_t ipl)
276	{	223	{
277	switch (rc) {	224	switch (rc) {
278	case ESYNCH_WOULD_BLOCK:	225	case ESYNCH_WOULD_BLOCK:
279	case ESYNCH_OK_ATOMIC:	226	case ESYNCH_OK_ATOMIC:
280	spinlock_unlock(&wq->lock);	227	spinlock_unlock(&wq->lock);
281	break;	228	break;
282	default:	229	default:
283	break;	230	break;
284	}	231	}
285	interrupts_restore(ipl);	232	interrupts_restore(ipl);
286	}	233	}
287		234
288	/** Internal implementation of waitq_sleep_timeout().	235	/** Internal implementation of waitq_sleep_timeout().
289	*	236	*
290	* This function implements logic of sleeping in a wait queue.	237	* This function implements logic of sleeping in a wait queue.
291	* This call must be preceeded by a call to waitq_sleep_prepare()	238	* This call must be preceeded by a call to waitq_sleep_prepare()
292	* and followed by a call to waitq_slee_finish().	239	* and followed by a call to waitq_slee_finish().
293	*	240	*
294	* @param wq See waitq_sleep_timeout().	241	* @param wq See waitq_sleep_timeout().
295	* @param usec See waitq_sleep_timeout().	242	* @param usec See waitq_sleep_timeout().
296	* @param flags See waitq_sleep_timeout().	243	* @param flags See waitq_sleep_timeout().
297	*	244	*
298	* @return See waitq_sleep_timeout().	245	* @return See waitq_sleep_timeout().
299	*/	246	*/
300	int waitq_sleep_timeout_unsafe(waitq_t *wq, uint32_t usec, int flags)	247	int waitq_sleep_timeout_unsafe(waitq_t *wq, uint32_t usec, int flags)
301	{	248	{
302	/* checks whether to go to sleep at all */	249	/* checks whether to go to sleep at all */
303	if (wq->missed_wakeups) {	250	if (wq->missed_wakeups) {
304	wq->missed_wakeups--;	251	wq->missed_wakeups--;
305	return ESYNCH_OK_ATOMIC;	252	return ESYNCH_OK_ATOMIC;
306	}	253	}
307	else {	254	else {
308	if ((flags & SYNCH_FLAGS_NON_BLOCKING) && (usec == 0)) {	255	if ((flags & SYNCH_FLAGS_NON_BLOCKING) && (usec == 0)) {
309	/* return immediatelly instead of going to sleep */	256	/* return immediatelly instead of going to sleep */
310	return ESYNCH_WOULD_BLOCK;	257	return ESYNCH_WOULD_BLOCK;
311	}	258	}
312	}	259	}
313		260
314	/*	261	/*
315	* Now we are firmly decided to go to sleep.	262	* Now we are firmly decided to go to sleep.
316	*/	263	*/
317	spinlock_lock(&THREAD->lock);	264	spinlock_lock(&THREAD->lock);
318		265
319	if (flags & SYNCH_FLAGS_INTERRUPTIBLE) {	266	if (flags & SYNCH_FLAGS_INTERRUPTIBLE) {
320		267
321	/*	268	/*
322	* If the thread was already interrupted,	269	* If the thread was already interrupted,
323	* don't go to sleep at all.	270	* don't go to sleep at all.
324	*/	271	*/
325	if (THREAD->interrupted) {	272	if (THREAD->interrupted) {
326	spinlock_unlock(&THREAD->lock);	273	spinlock_unlock(&THREAD->lock);
327	spinlock_unlock(&wq->lock);	274	spinlock_unlock(&wq->lock);
328	return ESYNCH_INTERRUPTED;	275	return ESYNCH_INTERRUPTED;
329	}	276	}
330		277
331	/*	278	/*
332	* Set context that will be restored if the sleep	279	* Set context that will be restored if the sleep
333	* of this thread is ever interrupted.	280	* of this thread is ever interrupted.
334	*/	281	*/
335	THREAD->sleep_interruptible = true;	282	THREAD->sleep_interruptible = true;
336	if (!context_save(&THREAD->sleep_interruption_context)) {	283	if (!context_save(&THREAD->sleep_interruption_context)) {
337	/* Short emulation of scheduler() return code. */	284	/* Short emulation of scheduler() return code. */
338	spinlock_unlock(&THREAD->lock);	285	spinlock_unlock(&THREAD->lock);
339	return ESYNCH_INTERRUPTED;	286	return ESYNCH_INTERRUPTED;
340	}	287	}
341		288
342	} else {	289	} else {
343	THREAD->sleep_interruptible = false;	290	THREAD->sleep_interruptible = false;
344	}	291	}
345		292
346	if (usec) {	293	if (usec) {
347	/* We use the timeout variant. */	294	/* We use the timeout variant. */
348	if (!context_save(&THREAD->sleep_timeout_context)) {	295	if (!context_save(&THREAD->sleep_timeout_context)) {
349	/* Short emulation of scheduler() return code. */	296	/* Short emulation of scheduler() return code. */
350	spinlock_unlock(&THREAD->lock);	297	spinlock_unlock(&THREAD->lock);
351	return ESYNCH_TIMEOUT;	298	return ESYNCH_TIMEOUT;
352	}	299	}
353	THREAD->timeout_pending = true;	300	THREAD->timeout_pending = true;
354	timeout_register(&THREAD->sleep_timeout, (uint64_t) usec,	301	timeout_register(&THREAD->sleep_timeout, (uint64_t) usec,
355	waitq_timeouted_sleep, THREAD);	302	waitq_timeouted_sleep, THREAD);
356	}	303	}
357		304
358	list_append(&THREAD->wq_link, &wq->head);	305	list_append(&THREAD->wq_link, &wq->head);
359		306
360	/*	307	/*
361	* Suspend execution.	308	* Suspend execution.
362	*/	309	*/
363	THREAD->state = Sleeping;	310	THREAD->state = Sleeping;
364	THREAD->sleep_queue = wq;	311	THREAD->sleep_queue = wq;
365		312
366	spinlock_unlock(&THREAD->lock);	313	spinlock_unlock(&THREAD->lock);
367		314
368	/* wq->lock is released in scheduler_separated_stack() */	315	/* wq->lock is released in scheduler_separated_stack() */
369	scheduler();	316	scheduler();
370		317
371	return ESYNCH_OK_BLOCKED;	318	return ESYNCH_OK_BLOCKED;
372	}	319	}
373		320
374		321
375	/** Wake up first thread sleeping in a wait queue	322	/** Wake up first thread sleeping in a wait queue
376	*	323	*
377	* Wake up first thread sleeping in a wait queue. This is the SMP- and IRQ-safe	324	* Wake up first thread sleeping in a wait queue. This is the SMP- and IRQ-safe
378	* wrapper meant for general use.	325	* wrapper meant for general use.
379	*	326	*
380	* Besides its 'normal' wakeup operation, it attempts to unregister possible	327	* Besides its 'normal' wakeup operation, it attempts to unregister possible
381	* timeout.	328	* timeout.
382	*	329	*
383	* @param wq Pointer to wait queue.	330	* @param wq Pointer to wait queue.
384	* @param all If this is non-zero, all sleeping threads will be woken up and	331	* @param all If this is non-zero, all sleeping threads will be woken up and
385	* missed count will be zeroed.	332	* missed count will be zeroed.
386	*/	333	*/
387	void waitq_wakeup(waitq_t *wq, bool all)	334	void waitq_wakeup(waitq_t *wq, bool all)
388	{	335	{
389	ipl_t ipl;	336	ipl_t ipl;
390		337
391	ipl = interrupts_disable();	338	ipl = interrupts_disable();
392	spinlock_lock(&wq->lock);	339	spinlock_lock(&wq->lock);
393		340
394	_waitq_wakeup_unsafe(wq, all);	341	_waitq_wakeup_unsafe(wq, all);
395		342
396	spinlock_unlock(&wq->lock);	343	spinlock_unlock(&wq->lock);
397	interrupts_restore(ipl);	344	interrupts_restore(ipl);
398	}	345	}
399		346
400	/** Internal SMP- and IRQ-unsafe version of waitq_wakeup()	347	/** Internal SMP- and IRQ-unsafe version of waitq_wakeup()
401	*	348	*
402	* This is the internal SMP- and IRQ-unsafe version of waitq_wakeup(). It	349	* This is the internal SMP- and IRQ-unsafe version of waitq_wakeup(). It
403	* assumes wq->lock is already locked and interrupts are already disabled.	350	* assumes wq->lock is already locked and interrupts are already disabled.
404	*	351	*
405	* @param wq Pointer to wait queue.	352	* @param wq Pointer to wait queue.
406	* @param all If this is non-zero, all sleeping threads will be woken up and	353	* @param all If this is non-zero, all sleeping threads will be woken up and
407	* missed count will be zeroed.	354	* missed count will be zeroed.
408	*/	355	*/
409	void _waitq_wakeup_unsafe(waitq_t *wq, bool all)	356	void _waitq_wakeup_unsafe(waitq_t *wq, bool all)
410	{	357	{
411	thread_t *t;	358	thread_t *t;
412		359
413	loop:	360	loop:
414	if (list_empty(&wq->head)) {	361	if (list_empty(&wq->head)) {
415	wq->missed_wakeups++;	362	wq->missed_wakeups++;
416	if (all)	363	if (all)
417	wq->missed_wakeups = 0;	364	wq->missed_wakeups = 0;
418	return;	365	return;
419	}	366	}
420		367
421	t = list_get_instance(wq->head.next, thread_t, wq_link);	368	t = list_get_instance(wq->head.next, thread_t, wq_link);
422		369
423	/*	370	/*
424	* Lock the thread prior to removing it from the wq.	371	* Lock the thread prior to removing it from the wq.
425	* This is not necessary because of mutual exclusion	372	* This is not necessary because of mutual exclusion
426	* (the link belongs to the wait queue), but because	373	* (the link belongs to the wait queue), but because
427	* of synchronization with waitq_timeouted_sleep()	374	* of synchronization with waitq_timeouted_sleep()
428	* and waitq_interrupt_sleep().	375	* and thread_interrupt_sleep().
429	*	376	*
430	* In order for these two functions to work, the following	377	* In order for these two functions to work, the following
431	* invariant must hold:	378	* invariant must hold:
432	*	379	*
433	* t->sleep_queue != NULL <=> t sleeps in a wait queue	380	* t->sleep_queue != NULL <=> t sleeps in a wait queue
434	*	381	*
435	* For an observer who locks the thread, the invariant	382	* For an observer who locks the thread, the invariant
436	* holds only when the lock is held prior to removing	383	* holds only when the lock is held prior to removing
437	* it from the wait queue.	384	* it from the wait queue.
438	*/	385	*/
439	spinlock_lock(&t->lock);	386	spinlock_lock(&t->lock);
440	list_remove(&t->wq_link);	387	list_remove(&t->wq_link);
441		388
442	if (t->timeout_pending && timeout_unregister(&t->sleep_timeout))	389	if (t->timeout_pending && timeout_unregister(&t->sleep_timeout))
443	t->timeout_pending = false;	390	t->timeout_pending = false;
444	t->sleep_queue = NULL;	391	t->sleep_queue = NULL;
445	spinlock_unlock(&t->lock);	392	spinlock_unlock(&t->lock);
446		393
447	thread_ready(t);	394	thread_ready(t);
448		395
449	if (all)	396	if (all)
450	goto loop;	397	goto loop;
451	}	398	}
452		399
453	/** @}	400	/** @}
454	*/	401	*/
455		402

Subversion Repositories HelenOS

(root)/trunk/kernel/generic/src/synch/waitq.c – Rev 2087 → 2089