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;
    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 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 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;
    count_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_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 (mode == WAKEUP_ALL)
        goto loop;
}
 
/** @}
 */
 

Rev 2183	Rev 2310
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	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 One of: ESYNCH_WOULD_BLOCK, ESYNCH_TIMEOUT, ESYNCH_INTERRUPTED,	203	* @return One of: ESYNCH_WOULD_BLOCK, ESYNCH_TIMEOUT, ESYNCH_INTERRUPTED,
204	* ESYNCH_OK_ATOMIC, ESYNCH_OK_BLOCKED.	204	* ESYNCH_OK_ATOMIC, ESYNCH_OK_BLOCKED.
205	*	205	*
206	* @li ESYNCH_WOULD_BLOCK means that the sleep failed because at the time of the	206	* @li ESYNCH_WOULD_BLOCK means that the sleep failed because at the time of the
207	* call there was no pending wakeup.	207	* call there was no pending wakeup.
208	*	208	*
209	* @li ESYNCH_TIMEOUT means that the sleep timed out.	209	* @li ESYNCH_TIMEOUT means that the sleep timed out.
210	*	210	*
211	* @li ESYNCH_INTERRUPTED means that somebody interrupted the sleeping thread.	211	* @li ESYNCH_INTERRUPTED means that somebody interrupted the sleeping thread.
212	*	212	*
213	* @li ESYNCH_OK_ATOMIC means that the sleep succeeded and that there was	213	* @li ESYNCH_OK_ATOMIC means that the sleep succeeded and that there was
214	* a pending wakeup at the time of the call. The caller was not put	214	* a pending wakeup at the time of the call. The caller was not put
215	* asleep at all.	215	* asleep at all.
216	*	216	*
217	* @li ESYNCH_OK_BLOCKED means that the sleep succeeded; the full sleep was	217	* @li ESYNCH_OK_BLOCKED means that the sleep succeeded; the full sleep was
218	* attempted.	218	* attempted.
219	*/	219	*/
220	int waitq_sleep_timeout(waitq_t *wq, uint32_t usec, int flags)	220	int waitq_sleep_timeout(waitq_t *wq, uint32_t usec, int flags)
221	{	221	{
222	ipl_t ipl;	222	ipl_t ipl;
223	int rc;	223	int rc;
224		224
225	ipl = waitq_sleep_prepare(wq);	225	ipl = waitq_sleep_prepare(wq);
226	rc = waitq_sleep_timeout_unsafe(wq, usec, flags);	226	rc = waitq_sleep_timeout_unsafe(wq, usec, flags);
227	waitq_sleep_finish(wq, rc, ipl);	227	waitq_sleep_finish(wq, rc, ipl);
228	return rc;	228	return rc;
229	}	229	}
230		230
231	/** Prepare to sleep in a waitq.	231	/** Prepare to sleep in a waitq.
232	*	232	*
233	* This function will return holding the lock of the wait queue	233	* This function will return holding the lock of the wait queue
234	* and interrupts disabled.	234	* and interrupts disabled.
235	*	235	*
236	* @param wq Wait queue.	236	* @param wq Wait queue.
237	*	237	*
238	* @return Interrupt level as it existed on entry to this function.	238	* @return Interrupt level as it existed on entry to this function.
239	*/	239	*/
240	ipl_t waitq_sleep_prepare(waitq_t *wq)	240	ipl_t waitq_sleep_prepare(waitq_t *wq)
241	{	241	{
242	ipl_t ipl;	242	ipl_t ipl;
243		243
244	restart:	244	restart:
245	ipl = interrupts_disable();	245	ipl = interrupts_disable();
246		246
247	if (THREAD) { /* needed during system initiailzation */	247	if (THREAD) { /* needed during system initiailzation */
248	/*	248	/*
249	* Busy waiting for a delayed timeout.	249	* Busy waiting for a delayed timeout.
250	* This is an important fix for the race condition between	250	* This is an important fix for the race condition between
251	* a delayed timeout and a next call to waitq_sleep_timeout().	251	* a delayed timeout and a next call to waitq_sleep_timeout().
252	* Simply, the thread is not allowed to go to sleep if	252	* Simply, the thread is not allowed to go to sleep if
253	* there are timeouts in progress.	253	* there are timeouts in progress.
254	*/	254	*/
255	spinlock_lock(&THREAD->lock);	255	spinlock_lock(&THREAD->lock);
256	if (THREAD->timeout_pending) {	256	if (THREAD->timeout_pending) {
257	spinlock_unlock(&THREAD->lock);	257	spinlock_unlock(&THREAD->lock);
258	interrupts_restore(ipl);	258	interrupts_restore(ipl);
259	goto restart;	259	goto restart;
260	}	260	}
261	spinlock_unlock(&THREAD->lock);	261	spinlock_unlock(&THREAD->lock);
262	}	262	}
263		263
264	spinlock_lock(&wq->lock);	264	spinlock_lock(&wq->lock);
265	return ipl;	265	return ipl;
266	}	266	}
267		267
268	/** Finish waiting in a wait queue.	268	/** Finish waiting in a wait queue.
269	*	269	*
270	* This function restores interrupts to the state that existed prior	270	* This function restores interrupts to the state that existed prior
271	* to the call to waitq_sleep_prepare(). If necessary, the wait queue	271	* to the call to waitq_sleep_prepare(). If necessary, the wait queue
272	* lock is released.	272	* lock is released.
273	*	273	*
274	* @param wq Wait queue.	274	* @param wq Wait queue.
275	* @param rc Return code of waitq_sleep_timeout_unsafe().	275	* @param rc Return code of waitq_sleep_timeout_unsafe().
276	* @param ipl Interrupt level returned by waitq_sleep_prepare().	276	* @param ipl Interrupt level returned by waitq_sleep_prepare().
277	*/	277	*/
278	void waitq_sleep_finish(waitq_t *wq, int rc, ipl_t ipl)	278	void waitq_sleep_finish(waitq_t *wq, int rc, ipl_t ipl)
279	{	279	{
280	switch (rc) {	280	switch (rc) {
281	case ESYNCH_WOULD_BLOCK:	281	case ESYNCH_WOULD_BLOCK:
282	case ESYNCH_OK_ATOMIC:	282	case ESYNCH_OK_ATOMIC:
283	spinlock_unlock(&wq->lock);	283	spinlock_unlock(&wq->lock);
284	break;	284	break;
285	default:	285	default:
286	break;	286	break;
287	}	287	}
288	interrupts_restore(ipl);	288	interrupts_restore(ipl);
289	}	289	}
290		290
291	/** Internal implementation of waitq_sleep_timeout().	291	/** Internal implementation of waitq_sleep_timeout().
292	*	292	*
293	* This function implements logic of sleeping in a wait queue.	293	* This function implements logic of sleeping in a wait queue.
294	* This call must be preceeded by a call to waitq_sleep_prepare()	294	* This call must be preceeded by a call to waitq_sleep_prepare()
295	* and followed by a call to waitq_slee_finish().	295	* and followed by a call to waitq_slee_finish().
296	*	296	*
297	* @param wq See waitq_sleep_timeout().	297	* @param wq See waitq_sleep_timeout().
298	* @param usec See waitq_sleep_timeout().	298	* @param usec See waitq_sleep_timeout().
299	* @param flags See waitq_sleep_timeout().	299	* @param flags See waitq_sleep_timeout().
300	*	300	*
301	* @return See waitq_sleep_timeout().	301	* @return See waitq_sleep_timeout().
302	*/	302	*/
303	int waitq_sleep_timeout_unsafe(waitq_t *wq, uint32_t usec, int flags)	303	int waitq_sleep_timeout_unsafe(waitq_t *wq, uint32_t usec, int flags)
304	{	304	{
305	/* checks whether to go to sleep at all */	305	/* checks whether to go to sleep at all */
306	if (wq->missed_wakeups) {	306	if (wq->missed_wakeups) {
307	wq->missed_wakeups--;	307	wq->missed_wakeups--;
308	return ESYNCH_OK_ATOMIC;	308	return ESYNCH_OK_ATOMIC;
309	}	309	}
310	else {	310	else {
311	if ((flags & SYNCH_FLAGS_NON_BLOCKING) && (usec == 0)) {	311	if ((flags & SYNCH_FLAGS_NON_BLOCKING) && (usec == 0)) {
312	/* return immediatelly instead of going to sleep */	312	/* return immediatelly instead of going to sleep */
313	return ESYNCH_WOULD_BLOCK;	313	return ESYNCH_WOULD_BLOCK;
314	}	314	}
315	}	315	}
316		316
317	/*	317	/*
318	* Now we are firmly decided to go to sleep.	318	* Now we are firmly decided to go to sleep.
319	*/	319	*/
320	spinlock_lock(&THREAD->lock);	320	spinlock_lock(&THREAD->lock);
321		321
322	if (flags & SYNCH_FLAGS_INTERRUPTIBLE) {	322	if (flags & SYNCH_FLAGS_INTERRUPTIBLE) {
323		323
324	/*	324	/*
325	* If the thread was already interrupted,	325	* If the thread was already interrupted,
326	* don't go to sleep at all.	326	* don't go to sleep at all.
327	*/	327	*/
328	if (THREAD->interrupted) {	328	if (THREAD->interrupted) {
329	spinlock_unlock(&THREAD->lock);	329	spinlock_unlock(&THREAD->lock);
330	spinlock_unlock(&wq->lock);	330	spinlock_unlock(&wq->lock);
331	return ESYNCH_INTERRUPTED;	331	return ESYNCH_INTERRUPTED;
332	}	332	}
333		333
334	/*	334	/*
335	* Set context that will be restored if the sleep	335	* Set context that will be restored if the sleep
336	* of this thread is ever interrupted.	336	* of this thread is ever interrupted.
337	*/	337	*/
338	THREAD->sleep_interruptible = true;	338	THREAD->sleep_interruptible = true;
339	if (!context_save(&THREAD->sleep_interruption_context)) {	339	if (!context_save(&THREAD->sleep_interruption_context)) {
340	/* Short emulation of scheduler() return code. */	340	/* Short emulation of scheduler() return code. */
341	spinlock_unlock(&THREAD->lock);	341	spinlock_unlock(&THREAD->lock);
342	return ESYNCH_INTERRUPTED;	342	return ESYNCH_INTERRUPTED;
343	}	343	}
344		344
345	} else {	345	} else {
346	THREAD->sleep_interruptible = false;	346	THREAD->sleep_interruptible = false;
347	}	347	}
348		348
349	if (usec) {	349	if (usec) {
350	/* We use the timeout variant. */	350	/* We use the timeout variant. */
351	if (!context_save(&THREAD->sleep_timeout_context)) {	351	if (!context_save(&THREAD->sleep_timeout_context)) {
352	/* Short emulation of scheduler() return code. */	352	/* Short emulation of scheduler() return code. */
353	spinlock_unlock(&THREAD->lock);	353	spinlock_unlock(&THREAD->lock);
354	return ESYNCH_TIMEOUT;	354	return ESYNCH_TIMEOUT;
355	}	355	}
356	THREAD->timeout_pending = true;	356	THREAD->timeout_pending = true;
357	timeout_register(&THREAD->sleep_timeout, (uint64_t) usec,	357	timeout_register(&THREAD->sleep_timeout, (uint64_t) usec,
358	waitq_timeouted_sleep, THREAD);	358	waitq_timeouted_sleep, THREAD);
359	}	359	}
360		360
361	list_append(&THREAD->wq_link, &wq->head);	361	list_append(&THREAD->wq_link, &wq->head);
362		362
363	/*	363	/*
364	* Suspend execution.	364	* Suspend execution.
365	*/	365	*/
366	THREAD->state = Sleeping;	366	THREAD->state = Sleeping;
367	THREAD->sleep_queue = wq;	367	THREAD->sleep_queue = wq;
368		368
369	spinlock_unlock(&THREAD->lock);	369	spinlock_unlock(&THREAD->lock);
370		370
371	/* wq->lock is released in scheduler_separated_stack() */	371	/* wq->lock is released in scheduler_separated_stack() */
372	scheduler();	372	scheduler();
373		373
374	return ESYNCH_OK_BLOCKED;	374	return ESYNCH_OK_BLOCKED;
375	}	375	}
376		376
377		377
378	/** Wake up first thread sleeping in a wait queue	378	/** Wake up first thread sleeping in a wait queue
379	*	379	*
380	* Wake up first thread sleeping in a wait queue. This is the SMP- and IRQ-safe	380	* Wake up first thread sleeping in a wait queue. This is the SMP- and IRQ-safe
381	* wrapper meant for general use.	381	* wrapper meant for general use.
382	*	382	*
383	* Besides its 'normal' wakeup operation, it attempts to unregister possible	383	* Besides its 'normal' wakeup operation, it attempts to unregister possible
384	* timeout.	384	* timeout.
385	*	385	*
386	* @param wq Pointer to wait queue.	386	* @param wq Pointer to wait queue.
387	* @param all If this is non-zero, all sleeping threads will be woken up and	-
388	* missed count will be zeroed.	387	* @param mode Wakeup mode.
389	*/	388	*/
390	void waitq_wakeup(waitq_t *wq, bool all)	389	void waitq_wakeup(waitq_t *wq, wakeup_mode_t mode)
391	{	390	{
392	ipl_t ipl;	391	ipl_t ipl;
393		392
394	ipl = interrupts_disable();	393	ipl = interrupts_disable();
395	spinlock_lock(&wq->lock);	394	spinlock_lock(&wq->lock);
396		395
397	_waitq_wakeup_unsafe(wq, all);	396	_waitq_wakeup_unsafe(wq, mode);
398		397
399	spinlock_unlock(&wq->lock);	398	spinlock_unlock(&wq->lock);
400	interrupts_restore(ipl);	399	interrupts_restore(ipl);
401	}	400	}
402		401
403	/** Internal SMP- and IRQ-unsafe version of waitq_wakeup()	402	/** Internal SMP- and IRQ-unsafe version of waitq_wakeup()
404	*	403	*
405	* This is the internal SMP- and IRQ-unsafe version of waitq_wakeup(). It	404	* 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.	405	* assumes wq->lock is already locked and interrupts are already disabled.
407	*	406	*
408	* @param wq Pointer to wait queue.	407	* @param wq Pointer to wait queue.
409	* @param all If this is non-zero, all sleeping threads will be woken up and	408	* @param mode If mode is WAKEUP_FIRST, then the longest waiting thread,
-		409	* if any, is woken up. If mode is WAKEUP_ALL, then all
-		410	* waiting threads, if any, are woken up. If there are no
-		411	* waiting threads to be woken up, the missed wakeup is
410	* missed count will be zeroed.	412	* recorded in the wait queue.
411	*/	413	*/
412	void _waitq_wakeup_unsafe(waitq_t *wq, bool all)	414	void _waitq_wakeup_unsafe(waitq_t *wq, wakeup_mode_t mode)
413	{	415	{
414	thread_t *t;	416	thread_t *t;
-		417	count_t count = 0;
415		418
416	loop:	419	loop:
417	if (list_empty(&wq->head)) {	420	if (list_empty(&wq->head)) {
418	wq->missed_wakeups++;	421	wq->missed_wakeups++;
419	if (all)	422	if (count && mode == WAKEUP_ALL)
420	wq->missed_wakeups = 0;	423	wq->missed_wakeups--;
421	return;	424	return;
422	}	425	}
423		426
-		427	count++;
424	t = list_get_instance(wq->head.next, thread_t, wq_link);	428	t = list_get_instance(wq->head.next, thread_t, wq_link);
425		429
426	/*	430	/*
427	* Lock the thread prior to removing it from the wq.	431	* Lock the thread prior to removing it from the wq.
428	* This is not necessary because of mutual exclusion	432	* This is not necessary because of mutual exclusion
429	* (the link belongs to the wait queue), but because	433	* (the link belongs to the wait queue), but because
430	* of synchronization with waitq_timeouted_sleep()	434	* of synchronization with waitq_timeouted_sleep()
431	* and thread_interrupt_sleep().	435	* and thread_interrupt_sleep().
432	*	436	*
433	* In order for these two functions to work, the following	437	* In order for these two functions to work, the following
434	* invariant must hold:	438	* invariant must hold:
435	*	439	*
436	* t->sleep_queue != NULL <=> t sleeps in a wait queue	440	* t->sleep_queue != NULL <=> t sleeps in a wait queue
437	*	441	*
438	* For an observer who locks the thread, the invariant	442	* For an observer who locks the thread, the invariant
439	* holds only when the lock is held prior to removing	443	* holds only when the lock is held prior to removing
440	* it from the wait queue.	444	* it from the wait queue.
441	*/	445	*/
442	spinlock_lock(&t->lock);	446	spinlock_lock(&t->lock);
443	list_remove(&t->wq_link);	447	list_remove(&t->wq_link);
444		448
445	if (t->timeout_pending && timeout_unregister(&t->sleep_timeout))	449	if (t->timeout_pending && timeout_unregister(&t->sleep_timeout))
446	t->timeout_pending = false;	450	t->timeout_pending = false;
447	t->sleep_queue = NULL;	451	t->sleep_queue = NULL;
448	spinlock_unlock(&t->lock);	452	spinlock_unlock(&t->lock);
449		453
450	thread_ready(t);	454	thread_ready(t);
451		455
452	if (all)	456	if (mode == WAKEUP_ALL)
453	goto loop;	457	goto loop;
454	}	458	}
455		459
456	/** @}	460	/** @}
457	*/	461	*/
458		462

Subversion Repositories HelenOS

(root)/trunk/kernel/generic/src/synch/waitq.c – Rev 2183 → 2310