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);
}
 
/** Interrupt sleeping thread.
 *
 * This routine attempts to interrupt a thread from its sleep in a waitqueue.
 * If the thread is not found sleeping, no action is taken.
 *
 * @param t Thread to be interrupted.
 */
void waitq_interrupt_sleep(thread_t *t)
{
    waitq_t *wq;
    bool do_wakeup = false;
    ipl_t ipl;
 
    ipl = interrupts_disable();
    spinlock_lock(&threads_lock);
    if (!thread_exists(t))
        goto out;
 
grab_locks:
    spinlock_lock(&t->lock);
    if ((wq = t->sleep_queue)) {        /* assignment */
        if (!(t->sleep_interruptible)) {
            /*
             * The sleep cannot be interrupted.
             */
            spinlock_unlock(&t->lock);
            goto out;
        }
           
        if (!spinlock_trylock(&wq->lock)) {
            spinlock_unlock(&t->lock);
            goto grab_locks;    /* avoid deadlock */
        }
 
        if (t->timeout_pending && timeout_unregister(&t->sleep_timeout))
            t->timeout_pending = false;
 
        list_remove(&t->wq_link);
        t->saved_context = t->sleep_interruption_context;
        do_wakeup = true;
        t->sleep_queue = NULL;
        spinlock_unlock(&wq->lock);
    }
    spinlock_unlock(&t->lock);
 
    if (do_wakeup)
        thread_ready(t);
 
out:
    spinlock_unlock(&threads_lock);
    interrupts_restore(ipl);
}
 
/** 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 2089	Rev 2109
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 <time/timeout.h>	52	#include <time/timeout.h>
53	#include <arch.h>	53	#include <arch.h>
54	#include <context.h>	54	#include <context.h>
55	#include <adt/list.h>	55	#include <adt/list.h>
56		56
57	static void waitq_timeouted_sleep(void *data);	57	static void waitq_timeouted_sleep(void *data);
58		58
59	/** Initialize wait queue	59	/** Initialize wait queue
60	*	60	*
61	* Initialize wait queue.	61	* Initialize wait queue.
62	*	62	*
63	* @param wq Pointer to wait queue to be initialized.	63	* @param wq Pointer to wait queue to be initialized.
64	*/	64	*/
65	void waitq_initialize(waitq_t *wq)	65	void waitq_initialize(waitq_t *wq)
66	{	66	{
67	spinlock_initialize(&wq->lock, "waitq_lock");	67	spinlock_initialize(&wq->lock, "waitq_lock");
68	list_initialize(&wq->head);	68	list_initialize(&wq->head);
69	wq->missed_wakeups = 0;	69	wq->missed_wakeups = 0;
70	}	70	}
71		71
72	/** Handle timeout during waitq_sleep_timeout() call	72	/** Handle timeout during waitq_sleep_timeout() call
73	*	73	*
74	* This routine is called when waitq_sleep_timeout() timeouts.	74	* This routine is called when waitq_sleep_timeout() timeouts.
75	* Interrupts are disabled.	75	* Interrupts are disabled.
76	*	76	*
77	* 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;
78	* 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
79	* 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
80	* timeout at all.	80	* timeout at all.
81	*	81	*
82	* @param data Pointer to the thread that called waitq_sleep_timeout().	82	* @param data Pointer to the thread that called waitq_sleep_timeout().
83	*/	83	*/
84	void waitq_timeouted_sleep(void *data)	84	void waitq_timeouted_sleep(void *data)
85	{	85	{
86	thread_t t = (thread_t ) data;	86	thread_t t = (thread_t ) data;
87	waitq_t *wq;	87	waitq_t *wq;
88	bool do_wakeup = false;	88	bool do_wakeup = false;
89		89
90	spinlock_lock(&threads_lock);	90	spinlock_lock(&threads_lock);
91	if (!thread_exists(t))	91	if (!thread_exists(t))
92	goto out;	92	goto out;
93		93
94	grab_locks:	94	grab_locks:
95	spinlock_lock(&t->lock);	95	spinlock_lock(&t->lock);
96	if ((wq = t->sleep_queue)) { /* assignment */	96	if ((wq = t->sleep_queue)) { /* assignment */
97	if (!spinlock_trylock(&wq->lock)) {	97	if (!spinlock_trylock(&wq->lock)) {
98	spinlock_unlock(&t->lock);	98	spinlock_unlock(&t->lock);
99	goto grab_locks; /* avoid deadlock */	99	goto grab_locks; /* avoid deadlock */
100	}	100	}
101		101
102	list_remove(&t->wq_link);	102	list_remove(&t->wq_link);
103	t->saved_context = t->sleep_timeout_context;	103	t->saved_context = t->sleep_timeout_context;
104	do_wakeup = true;	104	do_wakeup = true;
105	t->sleep_queue = NULL;	105	t->sleep_queue = NULL;
106	spinlock_unlock(&wq->lock);	106	spinlock_unlock(&wq->lock);
107	}	107	}
108		108
109	t->timeout_pending = false;	109	t->timeout_pending = false;
110	spinlock_unlock(&t->lock);	110	spinlock_unlock(&t->lock);
111		111
112	if (do_wakeup)	112	if (do_wakeup)
113	thread_ready(t);	113	thread_ready(t);
114		114
115	out:	115	out:
116	spinlock_unlock(&threads_lock);	116	spinlock_unlock(&threads_lock);
117	}	117	}
118		118
-		119	/** Interrupt sleeping thread.
-		120	*
-		121	* This routine attempts to interrupt a thread from its sleep in a waitqueue.
-		122	* If the thread is not found sleeping, no action is taken.
-		123	*
-		124	* @param t Thread to be interrupted.
-		125	*/
-		126	void waitq_interrupt_sleep(thread_t *t)
-		127	{
-		128	waitq_t *wq;
-		129	bool do_wakeup = false;
-		130	ipl_t ipl;
-		131
-		132	ipl = interrupts_disable();
-		133	spinlock_lock(&threads_lock);
-		134	if (!thread_exists(t))
-		135	goto out;
-		136
-		137	grab_locks:
-		138	spinlock_lock(&t->lock);
-		139	if ((wq = t->sleep_queue)) { /* assignment */
-		140	if (!(t->sleep_interruptible)) {
-		141	/*
-		142	* The sleep cannot be interrupted.
-		143	*/
-		144	spinlock_unlock(&t->lock);
-		145	goto out;
-		146	}
-		147
-		148	if (!spinlock_trylock(&wq->lock)) {
-		149	spinlock_unlock(&t->lock);
-		150	goto grab_locks; /* avoid deadlock */
-		151	}
-		152
-		153	if (t->timeout_pending && timeout_unregister(&t->sleep_timeout))
-		154	t->timeout_pending = false;
-		155
-		156	list_remove(&t->wq_link);
-		157	t->saved_context = t->sleep_interruption_context;
-		158	do_wakeup = true;
-		159	t->sleep_queue = NULL;
-		160	spinlock_unlock(&wq->lock);
-		161	}
-		162	spinlock_unlock(&t->lock);
-		163
-		164	if (do_wakeup)
-		165	thread_ready(t);
-		166
-		167	out:
-		168	spinlock_unlock(&threads_lock);
-		169	interrupts_restore(ipl);
-		170	}
119		171
120	/** Sleep until either wakeup, timeout or interruption occurs	172	/** Sleep until either wakeup, timeout or interruption occurs
121	*	173	*
122	* This is a sleep implementation which allows itself to time out or to be	174	* This is a sleep implementation which allows itself to time out or to be
123	* interrupted from the sleep, restoring a failover context.	175	* interrupted from the sleep, restoring a failover context.
124	*	176	*
125	* Sleepers are organised in a FIFO fashion in a structure called wait queue.	177	* Sleepers are organised in a FIFO fashion in a structure called wait queue.
126	*	178	*
127	* This function is really basic in that other functions as waitq_sleep()	179	* This function is really basic in that other functions as waitq_sleep()
128	* and all the *_timeout() functions use it.	180	* and all the *_timeout() functions use it.
129	*	181	*
130	* @param wq Pointer to wait queue.	182	* @param wq Pointer to wait queue.
131	* @param usec Timeout in microseconds.	183	* @param usec Timeout in microseconds.
132	* @param flags Specify mode of the sleep.	184	* @param flags Specify mode of the sleep.
133	*	185	*
134	* The sleep can be interrupted only if the	186	* The sleep can be interrupted only if the
135	* SYNCH_FLAGS_INTERRUPTIBLE bit is specified in flags.	187	* SYNCH_FLAGS_INTERRUPTIBLE bit is specified in flags.
136	*	188	*
137	* If usec is greater than zero, regardless of the value of the	189	* If usec is greater than zero, regardless of the value of the
138	* SYNCH_FLAGS_NON_BLOCKING bit in flags, the call will not return until either	190	* SYNCH_FLAGS_NON_BLOCKING bit in flags, the call will not return until either
139	* timeout, interruption or wakeup comes.	191	* timeout, interruption or wakeup comes.
140	*	192	*
141	* If usec is zero and the SYNCH_FLAGS_NON_BLOCKING bit is not set in flags,	193	* If usec is zero and the SYNCH_FLAGS_NON_BLOCKING bit is not set in flags,
142	* the call will not return until wakeup or interruption comes.	194	* the call will not return until wakeup or interruption comes.
143	*	195	*
144	* If usec is zero and the SYNCH_FLAGS_NON_BLOCKING bit is set in flags, the	196	* If usec is zero and the SYNCH_FLAGS_NON_BLOCKING bit is set in flags, the
145	* call will immediately return, reporting either success or failure.	197	* call will immediately return, reporting either success or failure.
146	*	198	*
147	* @return One of: ESYNCH_WOULD_BLOCK, ESYNCH_TIMEOUT, ESYNCH_INTERRUPTED,	199	* @return One of: ESYNCH_WOULD_BLOCK, ESYNCH_TIMEOUT, ESYNCH_INTERRUPTED,
148	* ESYNCH_OK_ATOMIC, ESYNCH_OK_BLOCKED.	200	* ESYNCH_OK_ATOMIC, ESYNCH_OK_BLOCKED.
149	*	201	*
150	* @li ESYNCH_WOULD_BLOCK means that the sleep failed because at the time of the	202	* @li ESYNCH_WOULD_BLOCK means that the sleep failed because at the time of the
151	* call there was no pending wakeup.	203	* call there was no pending wakeup.
152	*	204	*
153	* @li ESYNCH_TIMEOUT means that the sleep timed out.	205	* @li ESYNCH_TIMEOUT means that the sleep timed out.
154	*	206	*
155	* @li ESYNCH_INTERRUPTED means that somebody interrupted the sleeping thread.	207	* @li ESYNCH_INTERRUPTED means that somebody interrupted the sleeping thread.
156	*	208	*
157	* @li ESYNCH_OK_ATOMIC means that the sleep succeeded and that there was	209	* @li ESYNCH_OK_ATOMIC means that the sleep succeeded and that there was
158	* a pending wakeup at the time of the call. The caller was not put	210	* a pending wakeup at the time of the call. The caller was not put
159	* asleep at all.	211	* asleep at all.
160	*	212	*
161	* @li ESYNCH_OK_BLOCKED means that the sleep succeeded; the full sleep was	213	* @li ESYNCH_OK_BLOCKED means that the sleep succeeded; the full sleep was
162	* attempted.	214	* attempted.
163	*/	215	*/
164	int waitq_sleep_timeout(waitq_t *wq, uint32_t usec, int flags)	216	int waitq_sleep_timeout(waitq_t *wq, uint32_t usec, int flags)
165	{	217	{
166	ipl_t ipl;	218	ipl_t ipl;
167	int rc;	219	int rc;
168		220
169	ipl = waitq_sleep_prepare(wq);	221	ipl = waitq_sleep_prepare(wq);
170	rc = waitq_sleep_timeout_unsafe(wq, usec, flags);	222	rc = waitq_sleep_timeout_unsafe(wq, usec, flags);
171	waitq_sleep_finish(wq, rc, ipl);	223	waitq_sleep_finish(wq, rc, ipl);
172	return rc;	224	return rc;
173	}	225	}
174		226
175	/** Prepare to sleep in a waitq.	227	/** Prepare to sleep in a waitq.
176	*	228	*
177	* This function will return holding the lock of the wait queue	229	* This function will return holding the lock of the wait queue
178	* and interrupts disabled.	230	* and interrupts disabled.
179	*	231	*
180	* @param wq Wait queue.	232	* @param wq Wait queue.
181	*	233	*
182	* @return Interrupt level as it existed on entry to this function.	234	* @return Interrupt level as it existed on entry to this function.
183	*/	235	*/
184	ipl_t waitq_sleep_prepare(waitq_t *wq)	236	ipl_t waitq_sleep_prepare(waitq_t *wq)
185	{	237	{
186	ipl_t ipl;	238	ipl_t ipl;
187		239
188	restart:	240	restart:
189	ipl = interrupts_disable();	241	ipl = interrupts_disable();
190		242
191	if (THREAD) { /* needed during system initiailzation */	243	if (THREAD) { /* needed during system initiailzation */
192	/*	244	/*
193	* Busy waiting for a delayed timeout.	245	* Busy waiting for a delayed timeout.
194	* This is an important fix for the race condition between	246	* This is an important fix for the race condition between
195	* a delayed timeout and a next call to waitq_sleep_timeout().	247	* a delayed timeout and a next call to waitq_sleep_timeout().
196	* Simply, the thread is not allowed to go to sleep if	248	* Simply, the thread is not allowed to go to sleep if
197	* there are timeouts in progress.	249	* there are timeouts in progress.
198	*/	250	*/
199	spinlock_lock(&THREAD->lock);	251	spinlock_lock(&THREAD->lock);
200	if (THREAD->timeout_pending) {	252	if (THREAD->timeout_pending) {
201	spinlock_unlock(&THREAD->lock);	253	spinlock_unlock(&THREAD->lock);
202	interrupts_restore(ipl);	254	interrupts_restore(ipl);
203	goto restart;	255	goto restart;
204	}	256	}
205	spinlock_unlock(&THREAD->lock);	257	spinlock_unlock(&THREAD->lock);
206	}	258	}
207		259
208	spinlock_lock(&wq->lock);	260	spinlock_lock(&wq->lock);
209	return ipl;	261	return ipl;
210	}	262	}
211		263
212	/** Finish waiting in a wait queue.	264	/** Finish waiting in a wait queue.
213	*	265	*
214	* This function restores interrupts to the state that existed prior	266	* This function restores interrupts to the state that existed prior
215	* to the call to waitq_sleep_prepare(). If necessary, the wait queue	267	* to the call to waitq_sleep_prepare(). If necessary, the wait queue
216	* lock is released.	268	* lock is released.
217	*	269	*
218	* @param wq Wait queue.	270	* @param wq Wait queue.
219	* @param rc Return code of waitq_sleep_timeout_unsafe().	271	* @param rc Return code of waitq_sleep_timeout_unsafe().
220	* @param ipl Interrupt level returned by waitq_sleep_prepare().	272	* @param ipl Interrupt level returned by waitq_sleep_prepare().
221	*/	273	*/
222	void waitq_sleep_finish(waitq_t *wq, int rc, ipl_t ipl)	274	void waitq_sleep_finish(waitq_t *wq, int rc, ipl_t ipl)
223	{	275	{
224	switch (rc) {	276	switch (rc) {
225	case ESYNCH_WOULD_BLOCK:	277	case ESYNCH_WOULD_BLOCK:
226	case ESYNCH_OK_ATOMIC:	278	case ESYNCH_OK_ATOMIC:
227	spinlock_unlock(&wq->lock);	279	spinlock_unlock(&wq->lock);
228	break;	280	break;
229	default:	281	default:
230	break;	282	break;
231	}	283	}
232	interrupts_restore(ipl);	284	interrupts_restore(ipl);
233	}	285	}
234		286
235	/** Internal implementation of waitq_sleep_timeout().	287	/** Internal implementation of waitq_sleep_timeout().
236	*	288	*
237	* This function implements logic of sleeping in a wait queue.	289	* This function implements logic of sleeping in a wait queue.
238	* This call must be preceeded by a call to waitq_sleep_prepare()	290	* This call must be preceeded by a call to waitq_sleep_prepare()
239	* and followed by a call to waitq_slee_finish().	291	* and followed by a call to waitq_slee_finish().
240	*	292	*
241	* @param wq See waitq_sleep_timeout().	293	* @param wq See waitq_sleep_timeout().
242	* @param usec See waitq_sleep_timeout().	294	* @param usec See waitq_sleep_timeout().
243	* @param flags See waitq_sleep_timeout().	295	* @param flags See waitq_sleep_timeout().
244	*	296	*
245	* @return See waitq_sleep_timeout().	297	* @return See waitq_sleep_timeout().
246	*/	298	*/
247	int waitq_sleep_timeout_unsafe(waitq_t *wq, uint32_t usec, int flags)	299	int waitq_sleep_timeout_unsafe(waitq_t *wq, uint32_t usec, int flags)
248	{	300	{
249	/* checks whether to go to sleep at all */	301	/* checks whether to go to sleep at all */
250	if (wq->missed_wakeups) {	302	if (wq->missed_wakeups) {
251	wq->missed_wakeups--;	303	wq->missed_wakeups--;
252	return ESYNCH_OK_ATOMIC;	304	return ESYNCH_OK_ATOMIC;
253	}	305	}
254	else {	306	else {
255	if ((flags & SYNCH_FLAGS_NON_BLOCKING) && (usec == 0)) {	307	if ((flags & SYNCH_FLAGS_NON_BLOCKING) && (usec == 0)) {
256	/* return immediatelly instead of going to sleep */	308	/* return immediatelly instead of going to sleep */
257	return ESYNCH_WOULD_BLOCK;	309	return ESYNCH_WOULD_BLOCK;
258	}	310	}
259	}	311	}
260		312
261	/*	313	/*
262	* Now we are firmly decided to go to sleep.	314	* Now we are firmly decided to go to sleep.
263	*/	315	*/
264	spinlock_lock(&THREAD->lock);	316	spinlock_lock(&THREAD->lock);
265		317
266	if (flags & SYNCH_FLAGS_INTERRUPTIBLE) {	318	if (flags & SYNCH_FLAGS_INTERRUPTIBLE) {
267		319
268	/*	320	/*
269	* If the thread was already interrupted,	321	* If the thread was already interrupted,
270	* don't go to sleep at all.	322	* don't go to sleep at all.
271	*/	323	*/
272	if (THREAD->interrupted) {	324	if (THREAD->interrupted) {
273	spinlock_unlock(&THREAD->lock);	325	spinlock_unlock(&THREAD->lock);
274	spinlock_unlock(&wq->lock);	326	spinlock_unlock(&wq->lock);
275	return ESYNCH_INTERRUPTED;	327	return ESYNCH_INTERRUPTED;
276	}	328	}
277		329
278	/*	330	/*
279	* Set context that will be restored if the sleep	331	* Set context that will be restored if the sleep
280	* of this thread is ever interrupted.	332	* of this thread is ever interrupted.
281	*/	333	*/
282	THREAD->sleep_interruptible = true;	334	THREAD->sleep_interruptible = true;
283	if (!context_save(&THREAD->sleep_interruption_context)) {	335	if (!context_save(&THREAD->sleep_interruption_context)) {
284	/* Short emulation of scheduler() return code. */	336	/* Short emulation of scheduler() return code. */
285	spinlock_unlock(&THREAD->lock);	337	spinlock_unlock(&THREAD->lock);
286	return ESYNCH_INTERRUPTED;	338	return ESYNCH_INTERRUPTED;
287	}	339	}
288		340
289	} else {	341	} else {
290	THREAD->sleep_interruptible = false;	342	THREAD->sleep_interruptible = false;
291	}	343	}
292		344
293	if (usec) {	345	if (usec) {
294	/* We use the timeout variant. */	346	/* We use the timeout variant. */
295	if (!context_save(&THREAD->sleep_timeout_context)) {	347	if (!context_save(&THREAD->sleep_timeout_context)) {
296	/* Short emulation of scheduler() return code. */	348	/* Short emulation of scheduler() return code. */
297	spinlock_unlock(&THREAD->lock);	349	spinlock_unlock(&THREAD->lock);
298	return ESYNCH_TIMEOUT;	350	return ESYNCH_TIMEOUT;
299	}	351	}
300	THREAD->timeout_pending = true;	352	THREAD->timeout_pending = true;
301	timeout_register(&THREAD->sleep_timeout, (uint64_t) usec,	353	timeout_register(&THREAD->sleep_timeout, (uint64_t) usec,
302	waitq_timeouted_sleep, THREAD);	354	waitq_timeouted_sleep, THREAD);
303	}	355	}
304		356
305	list_append(&THREAD->wq_link, &wq->head);	357	list_append(&THREAD->wq_link, &wq->head);
306		358
307	/*	359	/*
308	* Suspend execution.	360	* Suspend execution.
309	*/	361	*/
310	THREAD->state = Sleeping;	362	THREAD->state = Sleeping;
311	THREAD->sleep_queue = wq;	363	THREAD->sleep_queue = wq;
312		364
313	spinlock_unlock(&THREAD->lock);	365	spinlock_unlock(&THREAD->lock);
314		366
315	/* wq->lock is released in scheduler_separated_stack() */	367	/* wq->lock is released in scheduler_separated_stack() */
316	scheduler();	368	scheduler();
317		369
318	return ESYNCH_OK_BLOCKED;	370	return ESYNCH_OK_BLOCKED;
319	}	371	}
320		372
321		373
322	/** Wake up first thread sleeping in a wait queue	374	/** Wake up first thread sleeping in a wait queue
323	*	375	*
324	* Wake up first thread sleeping in a wait queue. This is the SMP- and IRQ-safe	376	* Wake up first thread sleeping in a wait queue. This is the SMP- and IRQ-safe
325	* wrapper meant for general use.	377	* wrapper meant for general use.
326	*	378	*
327	* Besides its 'normal' wakeup operation, it attempts to unregister possible	379	* Besides its 'normal' wakeup operation, it attempts to unregister possible
328	* timeout.	380	* timeout.
329	*	381	*
330	* @param wq Pointer to wait queue.	382	* @param wq Pointer to wait queue.
331	* @param all If this is non-zero, all sleeping threads will be woken up and	383	* @param all If this is non-zero, all sleeping threads will be woken up and
332	* missed count will be zeroed.	384	* missed count will be zeroed.
333	*/	385	*/
334	void waitq_wakeup(waitq_t *wq, bool all)	386	void waitq_wakeup(waitq_t *wq, bool all)
335	{	387	{
336	ipl_t ipl;	388	ipl_t ipl;
337		389
338	ipl = interrupts_disable();	390	ipl = interrupts_disable();
339	spinlock_lock(&wq->lock);	391	spinlock_lock(&wq->lock);
340		392
341	_waitq_wakeup_unsafe(wq, all);	393	_waitq_wakeup_unsafe(wq, all);
342		394
343	spinlock_unlock(&wq->lock);	395	spinlock_unlock(&wq->lock);
344	interrupts_restore(ipl);	396	interrupts_restore(ipl);
345	}	397	}
346		398
347	/** Internal SMP- and IRQ-unsafe version of waitq_wakeup()	399	/** Internal SMP- and IRQ-unsafe version of waitq_wakeup()
348	*	400	*
349	* This is the internal SMP- and IRQ-unsafe version of waitq_wakeup(). It	401	* This is the internal SMP- and IRQ-unsafe version of waitq_wakeup(). It
350	* assumes wq->lock is already locked and interrupts are already disabled.	402	* assumes wq->lock is already locked and interrupts are already disabled.
351	*	403	*
352	* @param wq Pointer to wait queue.	404	* @param wq Pointer to wait queue.
353	* @param all If this is non-zero, all sleeping threads will be woken up and	405	* @param all If this is non-zero, all sleeping threads will be woken up and
354	* missed count will be zeroed.	406	* missed count will be zeroed.
355	*/	407	*/
356	void _waitq_wakeup_unsafe(waitq_t *wq, bool all)	408	void _waitq_wakeup_unsafe(waitq_t *wq, bool all)
357	{	409	{
358	thread_t *t;	410	thread_t *t;
359		411
360	loop:	412	loop:
361	if (list_empty(&wq->head)) {	413	if (list_empty(&wq->head)) {
362	wq->missed_wakeups++;	414	wq->missed_wakeups++;
363	if (all)	415	if (all)
364	wq->missed_wakeups = 0;	416	wq->missed_wakeups = 0;
365	return;	417	return;
366	}	418	}
367		419
368	t = list_get_instance(wq->head.next, thread_t, wq_link);	420	t = list_get_instance(wq->head.next, thread_t, wq_link);
369		421
370	/*	422	/*
371	* Lock the thread prior to removing it from the wq.	423	* Lock the thread prior to removing it from the wq.
372	* This is not necessary because of mutual exclusion	424	* This is not necessary because of mutual exclusion
373	* (the link belongs to the wait queue), but because	425	* (the link belongs to the wait queue), but because
374	* of synchronization with waitq_timeouted_sleep()	426	* of synchronization with waitq_timeouted_sleep()
375	* and thread_interrupt_sleep().	427	* and thread_interrupt_sleep().
376	*	428	*
377	* In order for these two functions to work, the following	429	* In order for these two functions to work, the following
378	* invariant must hold:	430	* invariant must hold:
379	*	431	*
380	* t->sleep_queue != NULL <=> t sleeps in a wait queue	432	* t->sleep_queue != NULL <=> t sleeps in a wait queue
381	*	433	*
382	* For an observer who locks the thread, the invariant	434	* For an observer who locks the thread, the invariant
383	* holds only when the lock is held prior to removing	435	* holds only when the lock is held prior to removing
384	* it from the wait queue.	436	* it from the wait queue.
385	*/	437	*/
386	spinlock_lock(&t->lock);	438	spinlock_lock(&t->lock);
387	list_remove(&t->wq_link);	439	list_remove(&t->wq_link);
388		440
389	if (t->timeout_pending && timeout_unregister(&t->sleep_timeout))	441	if (t->timeout_pending && timeout_unregister(&t->sleep_timeout))
390	t->timeout_pending = false;	442	t->timeout_pending = false;
391	t->sleep_queue = NULL;	443	t->sleep_queue = NULL;
392	spinlock_unlock(&t->lock);	444	spinlock_unlock(&t->lock);
393		445
394	thread_ready(t);	446	thread_ready(t);
395		447
396	if (all)	448	if (all)
397	goto loop;	449	goto loop;
398	}	450	}
399		451
400	/** @}	452	/** @}
401	*/	453	*/
402		454

Subversion Repositories HelenOS

(root)/trunk/kernel/generic/src/synch/waitq.c – Rev 2089 → 2109