WebSVN – HelenOS – Diff – /branches/tracing/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_sleep_timed_out(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() times out.
 * 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_sleep_timed_out(void *data)
{
    thread_t *t = (thread_t *) data;
    waitq_t *wq;
    bool do_wakeup = false;
    DEADLOCK_PROBE_INIT(p_wqlock);
 
    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);
            DEADLOCK_PROBE(p_wqlock, DEADLOCK_THRESHOLD);
            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;
    DEADLOCK_PROBE_INIT(p_wqlock);
 
    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);
            DEADLOCK_PROBE(p_wqlock, DEADLOCK_THRESHOLD);
            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      Returns one of ESYNCH_WOULD_BLOCK, ESYNCH_TIMEOUT,
 *          ESYNCH_INTERRUPTED, ESYNCH_OK_ATOMIC and
 *          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 preceded by a call to waitq_sleep_prepare()
 * and followed by a call to waitq_sleep_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_sleep_timed_out, 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 mode      Wakeup mode.
 */
void waitq_wakeup(waitq_t *wq, wakeup_mode_t mode)
{
    ipl_t ipl;
 
    ipl = interrupts_disable();
    spinlock_lock(&wq->lock);
 
    _waitq_wakeup_unsafe(wq, mode);
 
    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 mode      If mode is WAKEUP_FIRST, then the longest waiting
 *          thread, if any, is woken up. If mode is WAKEUP_ALL, then
 *          all waiting threads, if any, are woken up. If there are
 *          no waiting threads to be woken up, the missed wakeup is
 *          recorded in the wait queue.
 */
void _waitq_wakeup_unsafe(waitq_t *wq, wakeup_mode_t mode)
{
    thread_t *t;
    size_t count = 0;
 
loop:  
    if (list_empty(&wq->head)) {
        wq->missed_wakeups++;
        if (count && mode == WAKEUP_ALL)
            wq->missed_wakeups--;
        return;
    }
 
    count++;
    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_sleep_timed_out()
     * 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 (mode == WAKEUP_ALL)
        goto loop;
}
 
/** @}
 */
 

Rev 2925	Rev 4692
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_sleep_timed_out(void *data);	57	static void waitq_sleep_timed_out(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() times out.	74	* This routine is called when waitq_sleep_timeout() times out.
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_sleep_timed_out(void *data)	84	void waitq_sleep_timed_out(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	DEADLOCK_PROBE_INIT(p_wqlock);	89	DEADLOCK_PROBE_INIT(p_wqlock);
90		90
91	spinlock_lock(&threads_lock);	91	spinlock_lock(&threads_lock);
92	if (!thread_exists(t))	92	if (!thread_exists(t))
93	goto out;	93	goto out;
94		94
95	grab_locks:	95	grab_locks:
96	spinlock_lock(&t->lock);	96	spinlock_lock(&t->lock);
97	if ((wq = t->sleep_queue)) { /* assignment */	97	if ((wq = t->sleep_queue)) { /* assignment */
98	if (!spinlock_trylock(&wq->lock)) {	98	if (!spinlock_trylock(&wq->lock)) {
99	spinlock_unlock(&t->lock);	99	spinlock_unlock(&t->lock);
100	DEADLOCK_PROBE(p_wqlock, DEADLOCK_THRESHOLD);	100	DEADLOCK_PROBE(p_wqlock, DEADLOCK_THRESHOLD);
101	goto grab_locks; /* avoid deadlock */	101	goto grab_locks; /* avoid deadlock */
102	}	102	}
103		103
104	list_remove(&t->wq_link);	104	list_remove(&t->wq_link);
105	t->saved_context = t->sleep_timeout_context;	105	t->saved_context = t->sleep_timeout_context;
106	do_wakeup = true;	106	do_wakeup = true;
107	t->sleep_queue = NULL;	107	t->sleep_queue = NULL;
108	spinlock_unlock(&wq->lock);	108	spinlock_unlock(&wq->lock);
109	}	109	}
110		110
111	t->timeout_pending = false;	111	t->timeout_pending = false;
112	spinlock_unlock(&t->lock);	112	spinlock_unlock(&t->lock);
113		113
114	if (do_wakeup)	114	if (do_wakeup)
115	thread_ready(t);	115	thread_ready(t);
116		116
117	out:	117	out:
118	spinlock_unlock(&threads_lock);	118	spinlock_unlock(&threads_lock);
119	}	119	}
120		120
121	/** Interrupt sleeping thread.	121	/** Interrupt sleeping thread.
122	*	122	*
123	* This routine attempts to interrupt a thread from its sleep in a waitqueue.	123	* This routine attempts to interrupt a thread from its sleep in a waitqueue.
124	* If the thread is not found sleeping, no action is taken.	124	* If the thread is not found sleeping, no action is taken.
125	*	125	*
126	* @param t Thread to be interrupted.	126	* @param t Thread to be interrupted.
127	*/	127	*/
128	void waitq_interrupt_sleep(thread_t *t)	128	void waitq_interrupt_sleep(thread_t *t)
129	{	129	{
130	waitq_t *wq;	130	waitq_t *wq;
131	bool do_wakeup = false;	131	bool do_wakeup = false;
132	ipl_t ipl;	132	ipl_t ipl;
133	DEADLOCK_PROBE_INIT(p_wqlock);	133	DEADLOCK_PROBE_INIT(p_wqlock);
134		134
135	ipl = interrupts_disable();	135	ipl = interrupts_disable();
136	spinlock_lock(&threads_lock);	136	spinlock_lock(&threads_lock);
137	if (!thread_exists(t))	137	if (!thread_exists(t))
138	goto out;	138	goto out;
139		139
140	grab_locks:	140	grab_locks:
141	spinlock_lock(&t->lock);	141	spinlock_lock(&t->lock);
142	if ((wq = t->sleep_queue)) { /* assignment */	142	if ((wq = t->sleep_queue)) { /* assignment */
143	if (!(t->sleep_interruptible)) {	143	if (!(t->sleep_interruptible)) {
144	/*	144	/*
145	* The sleep cannot be interrupted.	145	* The sleep cannot be interrupted.
146	*/	146	*/
147	spinlock_unlock(&t->lock);	147	spinlock_unlock(&t->lock);
148	goto out;	148	goto out;
149	}	149	}
150		150
151	if (!spinlock_trylock(&wq->lock)) {	151	if (!spinlock_trylock(&wq->lock)) {
152	spinlock_unlock(&t->lock);	152	spinlock_unlock(&t->lock);
153	DEADLOCK_PROBE(p_wqlock, DEADLOCK_THRESHOLD);	153	DEADLOCK_PROBE(p_wqlock, DEADLOCK_THRESHOLD);
154	goto grab_locks; /* avoid deadlock */	154	goto grab_locks; /* avoid deadlock */
155	}	155	}
156		156
157	if (t->timeout_pending && timeout_unregister(&t->sleep_timeout))	157	if (t->timeout_pending && timeout_unregister(&t->sleep_timeout))
158	t->timeout_pending = false;	158	t->timeout_pending = false;
159		159
160	list_remove(&t->wq_link);	160	list_remove(&t->wq_link);
161	t->saved_context = t->sleep_interruption_context;	161	t->saved_context = t->sleep_interruption_context;
162	do_wakeup = true;	162	do_wakeup = true;
163	t->sleep_queue = NULL;	163	t->sleep_queue = NULL;
164	spinlock_unlock(&wq->lock);	164	spinlock_unlock(&wq->lock);
165	}	165	}
166	spinlock_unlock(&t->lock);	166	spinlock_unlock(&t->lock);
167		167
168	if (do_wakeup)	168	if (do_wakeup)
169	thread_ready(t);	169	thread_ready(t);
170		170
171	out:	171	out:
172	spinlock_unlock(&threads_lock);	172	spinlock_unlock(&threads_lock);
173	interrupts_restore(ipl);	173	interrupts_restore(ipl);
174	}	174	}
175		175
176	/** Sleep until either wakeup, timeout or interruption occurs	176	/** Sleep until either wakeup, timeout or interruption occurs
177	*	177	*
178	* This is a sleep implementation which allows itself to time out or to be	178	* This is a sleep implementation which allows itself to time out or to be
179	* interrupted from the sleep, restoring a failover context.	179	* interrupted from the sleep, restoring a failover context.
180	*	180	*
181	* Sleepers are organised in a FIFO fashion in a structure called wait queue.	181	* Sleepers are organised in a FIFO fashion in a structure called wait queue.
182	*	182	*
183	* This function is really basic in that other functions as waitq_sleep()	183	* This function is really basic in that other functions as waitq_sleep()
184	* and all the *_timeout() functions use it.	184	* and all the *_timeout() functions use it.
185	*	185	*
186	* @param wq Pointer to wait queue.	186	* @param wq Pointer to wait queue.
187	* @param usec Timeout in microseconds.	187	* @param usec Timeout in microseconds.
188	* @param flags Specify mode of the sleep.	188	* @param flags Specify mode of the sleep.
189	*	189	*
190	* The sleep can be interrupted only if the	190	* The sleep can be interrupted only if the
191	* SYNCH_FLAGS_INTERRUPTIBLE bit is specified in flags.	191	* SYNCH_FLAGS_INTERRUPTIBLE bit is specified in flags.
192	*	192	*
193	* If usec is greater than zero, regardless of the value of the	193	* If usec is greater than zero, regardless of the value of the
194	* SYNCH_FLAGS_NON_BLOCKING bit in flags, the call will not return until either	194	* SYNCH_FLAGS_NON_BLOCKING bit in flags, the call will not return until either
195	* timeout, interruption or wakeup comes.	195	* timeout, interruption or wakeup comes.
196	*	196	*
197	* If usec is zero and the SYNCH_FLAGS_NON_BLOCKING bit is not set in flags,	197	* If usec is zero and the SYNCH_FLAGS_NON_BLOCKING bit is not set in flags,
198	* the call will not return until wakeup or interruption comes.	198	* the call will not return until wakeup or interruption comes.
199	*	199	*
200	* If usec is zero and the SYNCH_FLAGS_NON_BLOCKING bit is set in flags, the	200	* If usec is zero and the SYNCH_FLAGS_NON_BLOCKING bit is set in flags, the
201	* call will immediately return, reporting either success or failure.	201	* call will immediately return, reporting either success or failure.
202	*	202	*
203	* @return Returns one of ESYNCH_WOULD_BLOCK, ESYNCH_TIMEOUT,	203	* @return Returns one of ESYNCH_WOULD_BLOCK, ESYNCH_TIMEOUT,
204	* ESYNCH_INTERRUPTED, ESYNCH_OK_ATOMIC and	204	* ESYNCH_INTERRUPTED, ESYNCH_OK_ATOMIC and
205	* ESYNCH_OK_BLOCKED.	205	* ESYNCH_OK_BLOCKED.
206	*	206	*
207	* @li ESYNCH_WOULD_BLOCK means that the sleep failed because at the time of	207	* @li ESYNCH_WOULD_BLOCK means that the sleep failed because at the time of
208	* the call there was no pending wakeup.	208	* the call there was no pending wakeup.
209	*	209	*
210	* @li ESYNCH_TIMEOUT means that the sleep timed out.	210	* @li ESYNCH_TIMEOUT means that the sleep timed out.
211	*	211	*
212	* @li ESYNCH_INTERRUPTED means that somebody interrupted the sleeping thread.	212	* @li ESYNCH_INTERRUPTED means that somebody interrupted the sleeping thread.
213	*	213	*
214	* @li ESYNCH_OK_ATOMIC means that the sleep succeeded and that there was	214	* @li ESYNCH_OK_ATOMIC means that the sleep succeeded and that there was
215	* a pending wakeup at the time of the call. The caller was not put	215	* a pending wakeup at the time of the call. The caller was not put
216	* asleep at all.	216	* asleep at all.
217	*	217	*
218	* @li ESYNCH_OK_BLOCKED means that the sleep succeeded; the full sleep was	218	* @li ESYNCH_OK_BLOCKED means that the sleep succeeded; the full sleep was
219	* attempted.	219	* attempted.
220	*/	220	*/
221	int waitq_sleep_timeout(waitq_t *wq, uint32_t usec, int flags)	221	int waitq_sleep_timeout(waitq_t *wq, uint32_t usec, int flags)
222	{	222	{
223	ipl_t ipl;	223	ipl_t ipl;
224	int rc;	224	int rc;
225		225
226	ipl = waitq_sleep_prepare(wq);	226	ipl = waitq_sleep_prepare(wq);
227	rc = waitq_sleep_timeout_unsafe(wq, usec, flags);	227	rc = waitq_sleep_timeout_unsafe(wq, usec, flags);
228	waitq_sleep_finish(wq, rc, ipl);	228	waitq_sleep_finish(wq, rc, ipl);
229	return rc;	229	return rc;
230	}	230	}
231		231
232	/** Prepare to sleep in a waitq.	232	/** Prepare to sleep in a waitq.
233	*	233	*
234	* This function will return holding the lock of the wait queue	234	* This function will return holding the lock of the wait queue
235	* and interrupts disabled.	235	* and interrupts disabled.
236	*	236	*
237	* @param wq Wait queue.	237	* @param wq Wait queue.
238	*	238	*
239	* @return Interrupt level as it existed on entry to this function.	239	* @return Interrupt level as it existed on entry to this function.
240	*/	240	*/
241	ipl_t waitq_sleep_prepare(waitq_t *wq)	241	ipl_t waitq_sleep_prepare(waitq_t *wq)
242	{	242	{
243	ipl_t ipl;	243	ipl_t ipl;
244		244
245	restart:	245	restart:
246	ipl = interrupts_disable();	246	ipl = interrupts_disable();
247		247
248	if (THREAD) { /* needed during system initiailzation */	248	if (THREAD) { /* needed during system initiailzation */
249	/*	249	/*
250	* Busy waiting for a delayed timeout.	250	* Busy waiting for a delayed timeout.
251	* This is an important fix for the race condition between	251	* This is an important fix for the race condition between
252	* a delayed timeout and a next call to waitq_sleep_timeout().	252	* a delayed timeout and a next call to waitq_sleep_timeout().
253	* Simply, the thread is not allowed to go to sleep if	253	* Simply, the thread is not allowed to go to sleep if
254	* there are timeouts in progress.	254	* there are timeouts in progress.
255	*/	255	*/
256	spinlock_lock(&THREAD->lock);	256	spinlock_lock(&THREAD->lock);
257	if (THREAD->timeout_pending) {	257	if (THREAD->timeout_pending) {
258	spinlock_unlock(&THREAD->lock);	258	spinlock_unlock(&THREAD->lock);
259	interrupts_restore(ipl);	259	interrupts_restore(ipl);
260	goto restart;	260	goto restart;
261	}	261	}
262	spinlock_unlock(&THREAD->lock);	262	spinlock_unlock(&THREAD->lock);
263	}	263	}
264		264
265	spinlock_lock(&wq->lock);	265	spinlock_lock(&wq->lock);
266	return ipl;	266	return ipl;
267	}	267	}
268		268
269	/** Finish waiting in a wait queue.	269	/** Finish waiting in a wait queue.
270	*	270	*
271	* This function restores interrupts to the state that existed prior	271	* This function restores interrupts to the state that existed prior
272	* to the call to waitq_sleep_prepare(). If necessary, the wait queue	272	* to the call to waitq_sleep_prepare(). If necessary, the wait queue
273	* lock is released.	273	* lock is released.
274	*	274	*
275	* @param wq Wait queue.	275	* @param wq Wait queue.
276	* @param rc Return code of waitq_sleep_timeout_unsafe().	276	* @param rc Return code of waitq_sleep_timeout_unsafe().
277	* @param ipl Interrupt level returned by waitq_sleep_prepare().	277	* @param ipl Interrupt level returned by waitq_sleep_prepare().
278	*/	278	*/
279	void waitq_sleep_finish(waitq_t *wq, int rc, ipl_t ipl)	279	void waitq_sleep_finish(waitq_t *wq, int rc, ipl_t ipl)
280	{	280	{
281	switch (rc) {	281	switch (rc) {
282	case ESYNCH_WOULD_BLOCK:	282	case ESYNCH_WOULD_BLOCK:
283	case ESYNCH_OK_ATOMIC:	283	case ESYNCH_OK_ATOMIC:
284	spinlock_unlock(&wq->lock);	284	spinlock_unlock(&wq->lock);
285	break;	285	break;
286	default:	286	default:
287	break;	287	break;
288	}	288	}
289	interrupts_restore(ipl);	289	interrupts_restore(ipl);
290	}	290	}
291		291
292	/** Internal implementation of waitq_sleep_timeout().	292	/** Internal implementation of waitq_sleep_timeout().
293	*	293	*
294	* This function implements logic of sleeping in a wait queue.	294	* This function implements logic of sleeping in a wait queue.
295	* This call must be preceded by a call to waitq_sleep_prepare()	295	* This call must be preceded by a call to waitq_sleep_prepare()
296	* and followed by a call to waitq_sleep_finish().	296	* and followed by a call to waitq_sleep_finish().
297	*	297	*
298	* @param wq See waitq_sleep_timeout().	298	* @param wq See waitq_sleep_timeout().
299	* @param usec See waitq_sleep_timeout().	299	* @param usec See waitq_sleep_timeout().
300	* @param flags See waitq_sleep_timeout().	300	* @param flags See waitq_sleep_timeout().
301	*	301	*
302	* @return See waitq_sleep_timeout().	302	* @return See waitq_sleep_timeout().
303	*/	303	*/
304	int waitq_sleep_timeout_unsafe(waitq_t *wq, uint32_t usec, int flags)	304	int waitq_sleep_timeout_unsafe(waitq_t *wq, uint32_t usec, int flags)
305	{	305	{
306	/* checks whether to go to sleep at all */	306	/* checks whether to go to sleep at all */
307	if (wq->missed_wakeups) {	307	if (wq->missed_wakeups) {
308	wq->missed_wakeups--;	308	wq->missed_wakeups--;
309	return ESYNCH_OK_ATOMIC;	309	return ESYNCH_OK_ATOMIC;
310	}	310	}
311	else {	311	else {
312	if ((flags & SYNCH_FLAGS_NON_BLOCKING) && (usec == 0)) {	312	if ((flags & SYNCH_FLAGS_NON_BLOCKING) && (usec == 0)) {
313	/* return immediatelly instead of going to sleep */	313	/* return immediatelly instead of going to sleep */
314	return ESYNCH_WOULD_BLOCK;	314	return ESYNCH_WOULD_BLOCK;
315	}	315	}
316	}	316	}
317		317
318	/*	318	/*
319	* Now we are firmly decided to go to sleep.	319	* Now we are firmly decided to go to sleep.
320	*/	320	*/
321	spinlock_lock(&THREAD->lock);	321	spinlock_lock(&THREAD->lock);
322		322
323	if (flags & SYNCH_FLAGS_INTERRUPTIBLE) {	323	if (flags & SYNCH_FLAGS_INTERRUPTIBLE) {
324		324
325	/*	325	/*
326	* If the thread was already interrupted,	326	* If the thread was already interrupted,
327	* don't go to sleep at all.	327	* don't go to sleep at all.
328	*/	328	*/
329	if (THREAD->interrupted) {	329	if (THREAD->interrupted) {
330	spinlock_unlock(&THREAD->lock);	330	spinlock_unlock(&THREAD->lock);
331	spinlock_unlock(&wq->lock);	331	spinlock_unlock(&wq->lock);
332	return ESYNCH_INTERRUPTED;	332	return ESYNCH_INTERRUPTED;
333	}	333	}
334		334
335	/*	335	/*
336	* Set context that will be restored if the sleep	336	* Set context that will be restored if the sleep
337	* of this thread is ever interrupted.	337	* of this thread is ever interrupted.
338	*/	338	*/
339	THREAD->sleep_interruptible = true;	339	THREAD->sleep_interruptible = true;
340	if (!context_save(&THREAD->sleep_interruption_context)) {	340	if (!context_save(&THREAD->sleep_interruption_context)) {
341	/* Short emulation of scheduler() return code. */	341	/* Short emulation of scheduler() return code. */
342	spinlock_unlock(&THREAD->lock);	342	spinlock_unlock(&THREAD->lock);
343	return ESYNCH_INTERRUPTED;	343	return ESYNCH_INTERRUPTED;
344	}	344	}
345		345
346	} else {	346	} else {
347	THREAD->sleep_interruptible = false;	347	THREAD->sleep_interruptible = false;
348	}	348	}
349		349
350	if (usec) {	350	if (usec) {
351	/* We use the timeout variant. */	351	/* We use the timeout variant. */
352	if (!context_save(&THREAD->sleep_timeout_context)) {	352	if (!context_save(&THREAD->sleep_timeout_context)) {
353	/* Short emulation of scheduler() return code. */	353	/* Short emulation of scheduler() return code. */
354	spinlock_unlock(&THREAD->lock);	354	spinlock_unlock(&THREAD->lock);
355	return ESYNCH_TIMEOUT;	355	return ESYNCH_TIMEOUT;
356	}	356	}
357	THREAD->timeout_pending = true;	357	THREAD->timeout_pending = true;
358	timeout_register(&THREAD->sleep_timeout, (uint64_t) usec,	358	timeout_register(&THREAD->sleep_timeout, (uint64_t) usec,
359	waitq_sleep_timed_out, THREAD);	359	waitq_sleep_timed_out, THREAD);
360	}	360	}
361		361
362	list_append(&THREAD->wq_link, &wq->head);	362	list_append(&THREAD->wq_link, &wq->head);
363		363
364	/*	364	/*
365	* Suspend execution.	365	* Suspend execution.
366	*/	366	*/
367	THREAD->state = Sleeping;	367	THREAD->state = Sleeping;
368	THREAD->sleep_queue = wq;	368	THREAD->sleep_queue = wq;
369		369
370	spinlock_unlock(&THREAD->lock);	370	spinlock_unlock(&THREAD->lock);
371		371
372	/* wq->lock is released in scheduler_separated_stack() */	372	/* wq->lock is released in scheduler_separated_stack() */
373	scheduler();	373	scheduler();
374		374
375	return ESYNCH_OK_BLOCKED;	375	return ESYNCH_OK_BLOCKED;
376	}	376	}
377		377
378		378
379	/** Wake up first thread sleeping in a wait queue	379	/** Wake up first thread sleeping in a wait queue
380	*	380	*
381	* Wake up first thread sleeping in a wait queue. This is the SMP- and IRQ-safe	381	* Wake up first thread sleeping in a wait queue. This is the SMP- and IRQ-safe
382	* wrapper meant for general use.	382	* wrapper meant for general use.
383	*	383	*
384	* Besides its 'normal' wakeup operation, it attempts to unregister possible	384	* Besides its 'normal' wakeup operation, it attempts to unregister possible
385	* timeout.	385	* timeout.
386	*	386	*
387	* @param wq Pointer to wait queue.	387	* @param wq Pointer to wait queue.
388	* @param mode Wakeup mode.	388	* @param mode Wakeup mode.
389	*/	389	*/
390	void waitq_wakeup(waitq_t *wq, wakeup_mode_t mode)	390	void waitq_wakeup(waitq_t *wq, wakeup_mode_t mode)
391	{	391	{
392	ipl_t ipl;	392	ipl_t ipl;
393		393
394	ipl = interrupts_disable();	394	ipl = interrupts_disable();
395	spinlock_lock(&wq->lock);	395	spinlock_lock(&wq->lock);
396		396
397	_waitq_wakeup_unsafe(wq, mode);	397	_waitq_wakeup_unsafe(wq, mode);
398		398
399	spinlock_unlock(&wq->lock);	399	spinlock_unlock(&wq->lock);
400	interrupts_restore(ipl);	400	interrupts_restore(ipl);
401	}	401	}
402		402
403	/** Internal SMP- and IRQ-unsafe version of waitq_wakeup()	403	/** Internal SMP- and IRQ-unsafe version of waitq_wakeup()
404	*	404	*
405	* This is the internal SMP- and IRQ-unsafe version of waitq_wakeup(). It	405	* This is the internal SMP- and IRQ-unsafe version of waitq_wakeup(). It
406	* assumes wq->lock is already locked and interrupts are already disabled.	406	* assumes wq->lock is already locked and interrupts are already disabled.
407	*	407	*
408	* @param wq Pointer to wait queue.	408	* @param wq Pointer to wait queue.
409	* @param mode If mode is WAKEUP_FIRST, then the longest waiting	409	* @param mode If mode is WAKEUP_FIRST, then the longest waiting
410	* thread, if any, is woken up. If mode is WAKEUP_ALL, then	410	* thread, if any, is woken up. If mode is WAKEUP_ALL, then
411	* all waiting threads, if any, are woken up. If there are	411	* all waiting threads, if any, are woken up. If there are
412	* no waiting threads to be woken up, the missed wakeup is	412	* no waiting threads to be woken up, the missed wakeup is
413	* recorded in the wait queue.	413	* recorded in the wait queue.
414	*/	414	*/
415	void _waitq_wakeup_unsafe(waitq_t *wq, wakeup_mode_t mode)	415	void _waitq_wakeup_unsafe(waitq_t *wq, wakeup_mode_t mode)
416	{	416	{
417	thread_t *t;	417	thread_t *t;
418	count_t count = 0;	418	size_t count = 0;
419		419
420	loop:	420	loop:
421	if (list_empty(&wq->head)) {	421	if (list_empty(&wq->head)) {
422	wq->missed_wakeups++;	422	wq->missed_wakeups++;
423	if (count && mode == WAKEUP_ALL)	423	if (count && mode == WAKEUP_ALL)
424	wq->missed_wakeups--;	424	wq->missed_wakeups--;
425	return;	425	return;
426	}	426	}
427		427
428	count++;	428	count++;
429	t = list_get_instance(wq->head.next, thread_t, wq_link);	429	t = list_get_instance(wq->head.next, thread_t, wq_link);
430		430
431	/*	431	/*
432	* Lock the thread prior to removing it from the wq.	432	* Lock the thread prior to removing it from the wq.
433	* This is not necessary because of mutual exclusion	433	* This is not necessary because of mutual exclusion
434	* (the link belongs to the wait queue), but because	434	* (the link belongs to the wait queue), but because
435	* of synchronization with waitq_sleep_timed_out()	435	* of synchronization with waitq_sleep_timed_out()
436	* and thread_interrupt_sleep().	436	* and thread_interrupt_sleep().
437	*	437	*
438	* In order for these two functions to work, the following	438	* In order for these two functions to work, the following
439	* invariant must hold:	439	* invariant must hold:
440	*	440	*
441	* t->sleep_queue != NULL <=> t sleeps in a wait queue	441	* t->sleep_queue != NULL <=> t sleeps in a wait queue
442	*	442	*
443	* For an observer who locks the thread, the invariant	443	* For an observer who locks the thread, the invariant
444	* holds only when the lock is held prior to removing	444	* holds only when the lock is held prior to removing
445	* it from the wait queue.	445	* it from the wait queue.
446	*/	446	*/
447	spinlock_lock(&t->lock);	447	spinlock_lock(&t->lock);
448	list_remove(&t->wq_link);	448	list_remove(&t->wq_link);
449		449
450	if (t->timeout_pending && timeout_unregister(&t->sleep_timeout))	450	if (t->timeout_pending && timeout_unregister(&t->sleep_timeout))
451	t->timeout_pending = false;	451	t->timeout_pending = false;
452	t->sleep_queue = NULL;	452	t->sleep_queue = NULL;
453	spinlock_unlock(&t->lock);	453	spinlock_unlock(&t->lock);
454		454
455	thread_ready(t);	455	thread_ready(t);
456		456
457	if (mode == WAKEUP_ALL)	457	if (mode == WAKEUP_ALL)
458	goto loop;	458	goto loop;
459	}	459	}
460		460
461	/** @}	461	/** @}
462	*/	462	*/
463		463

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(root)/branches/tracing/kernel/generic/src/synch/waitq.c – Rev 2925 → 4692