WebSVN – HelenOS-historic – Diff – /kernel/trunk/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 <typedefs.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  Returns 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, __u32 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, __u32 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, (__u64) 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);
 
    scheduler();    /* wq->lock is released in scheduler_separated_stack() */
   
    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 waitq_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 1681	Rev 1702
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
-		30	* @{
-		31	*/
-		32
29	/**	33	/**
30	* @file waitq.c	34	* @file
31	* @brief Wait queue.	35	* @brief Wait queue.
32	*	36	*
33	* Wait queue is the basic synchronization primitive upon which all	37	* Wait queue is the basic synchronization primitive upon which all
34	* other synchronization primitives build.	38	* other synchronization primitives build.
35	*	39	*
36	* 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
37	* fashion. Conditional operation as well as timeouts and interruptions	41	* fashion. Conditional operation as well as timeouts and interruptions
38	* are supported.	42	* are supported.
39	*/	43	*/
40		44
41	#include <synch/waitq.h>	45	#include <synch/waitq.h>
42	#include <synch/synch.h>	46	#include <synch/synch.h>
43	#include <synch/spinlock.h>	47	#include <synch/spinlock.h>
44	#include <proc/thread.h>	48	#include <proc/thread.h>
45	#include <proc/scheduler.h>	49	#include <proc/scheduler.h>
46	#include <arch/asm.h>	50	#include <arch/asm.h>
47	#include <arch/types.h>	51	#include <arch/types.h>
48	#include <typedefs.h>	52	#include <typedefs.h>
49	#include <time/timeout.h>	53	#include <time/timeout.h>
50	#include <arch.h>	54	#include <arch.h>
51	#include <context.h>	55	#include <context.h>
52	#include <adt/list.h>	56	#include <adt/list.h>
53		57
54	static void waitq_timeouted_sleep(void *data);	58	static void waitq_timeouted_sleep(void *data);
55		59
56	/** Initialize wait queue	60	/** Initialize wait queue
57	*	61	*
58	* Initialize wait queue.	62	* Initialize wait queue.
59	*	63	*
60	* @param wq Pointer to wait queue to be initialized.	64	* @param wq Pointer to wait queue to be initialized.
61	*/	65	*/
62	void waitq_initialize(waitq_t *wq)	66	void waitq_initialize(waitq_t *wq)
63	{	67	{
64	spinlock_initialize(&wq->lock, "waitq_lock");	68	spinlock_initialize(&wq->lock, "waitq_lock");
65	list_initialize(&wq->head);	69	list_initialize(&wq->head);
66	wq->missed_wakeups = 0;	70	wq->missed_wakeups = 0;
67	}	71	}
68		72
69	/** Handle timeout during waitq_sleep_timeout() call	73	/** Handle timeout during waitq_sleep_timeout() call
70	*	74	*
71	* This routine is called when waitq_sleep_timeout() timeouts.	75	* This routine is called when waitq_sleep_timeout() timeouts.
72	* Interrupts are disabled.	76	* Interrupts are disabled.
73	*	77	*
74	* It is supposed to try to remove 'its' thread from the wait queue;	78	* It is supposed to try to remove 'its' thread from the wait queue;
75	* it can eventually fail to achieve this goal when these two events	79	* it can eventually fail to achieve this goal when these two events
76	* overlap. In that case it behaves just as though there was no	80	* overlap. In that case it behaves just as though there was no
77	* timeout at all.	81	* timeout at all.
78	*	82	*
79	* @param data Pointer to the thread that called waitq_sleep_timeout().	83	* @param data Pointer to the thread that called waitq_sleep_timeout().
80	*/	84	*/
81	void waitq_timeouted_sleep(void *data)	85	void waitq_timeouted_sleep(void *data)
82	{	86	{
83	thread_t t = (thread_t ) data;	87	thread_t t = (thread_t ) data;
84	waitq_t *wq;	88	waitq_t *wq;
85	bool do_wakeup = false;	89	bool do_wakeup = false;
86		90
87	spinlock_lock(&threads_lock);	91	spinlock_lock(&threads_lock);
88	if (!thread_exists(t))	92	if (!thread_exists(t))
89	goto out;	93	goto out;
90		94
91	grab_locks:	95	grab_locks:
92	spinlock_lock(&t->lock);	96	spinlock_lock(&t->lock);
93	if ((wq = t->sleep_queue)) { /* assignment */	97	if ((wq = t->sleep_queue)) { /* assignment */
94	if (!spinlock_trylock(&wq->lock)) {	98	if (!spinlock_trylock(&wq->lock)) {
95	spinlock_unlock(&t->lock);	99	spinlock_unlock(&t->lock);
96	goto grab_locks; /* avoid deadlock */	100	goto grab_locks; /* avoid deadlock */
97	}	101	}
98		102
99	list_remove(&t->wq_link);	103	list_remove(&t->wq_link);
100	t->saved_context = t->sleep_timeout_context;	104	t->saved_context = t->sleep_timeout_context;
101	do_wakeup = true;	105	do_wakeup = true;
102	t->sleep_queue = NULL;	106	t->sleep_queue = NULL;
103	spinlock_unlock(&wq->lock);	107	spinlock_unlock(&wq->lock);
104	}	108	}
105		109
106	t->timeout_pending = false;	110	t->timeout_pending = false;
107	spinlock_unlock(&t->lock);	111	spinlock_unlock(&t->lock);
108		112
109	if (do_wakeup)	113	if (do_wakeup)
110	thread_ready(t);	114	thread_ready(t);
111		115
112	out:	116	out:
113	spinlock_unlock(&threads_lock);	117	spinlock_unlock(&threads_lock);
114	}	118	}
115		119
116	/** Interrupt sleeping thread.	120	/** Interrupt sleeping thread.
117	*	121	*
118	* This routine attempts to interrupt a thread from its sleep in a waitqueue.	122	* This routine attempts to interrupt a thread from its sleep in a waitqueue.
119	* If the thread is not found sleeping, no action is taken.	123	* If the thread is not found sleeping, no action is taken.
120	*	124	*
121	* @param t Thread to be interrupted.	125	* @param t Thread to be interrupted.
122	*/	126	*/
123	void waitq_interrupt_sleep(thread_t *t)	127	void waitq_interrupt_sleep(thread_t *t)
124	{	128	{
125	waitq_t *wq;	129	waitq_t *wq;
126	bool do_wakeup = false;	130	bool do_wakeup = false;
127	ipl_t ipl;	131	ipl_t ipl;
128		132
129	ipl = interrupts_disable();	133	ipl = interrupts_disable();
130	spinlock_lock(&threads_lock);	134	spinlock_lock(&threads_lock);
131	if (!thread_exists(t))	135	if (!thread_exists(t))
132	goto out;	136	goto out;
133		137
134	grab_locks:	138	grab_locks:
135	spinlock_lock(&t->lock);	139	spinlock_lock(&t->lock);
136	if ((wq = t->sleep_queue)) { /* assignment */	140	if ((wq = t->sleep_queue)) { /* assignment */
137	if (!(t->sleep_interruptible)) {	141	if (!(t->sleep_interruptible)) {
138	/*	142	/*
139	* The sleep cannot be interrupted.	143	* The sleep cannot be interrupted.
140	*/	144	*/
141	spinlock_unlock(&t->lock);	145	spinlock_unlock(&t->lock);
142	goto out;	146	goto out;
143	}	147	}
144		148
145	if (!spinlock_trylock(&wq->lock)) {	149	if (!spinlock_trylock(&wq->lock)) {
146	spinlock_unlock(&t->lock);	150	spinlock_unlock(&t->lock);
147	goto grab_locks; /* avoid deadlock */	151	goto grab_locks; /* avoid deadlock */
148	}	152	}
149		153
150	if (t->timeout_pending && timeout_unregister(&t->sleep_timeout))	154	if (t->timeout_pending && timeout_unregister(&t->sleep_timeout))
151	t->timeout_pending = false;	155	t->timeout_pending = false;
152		156
153	list_remove(&t->wq_link);	157	list_remove(&t->wq_link);
154	t->saved_context = t->sleep_interruption_context;	158	t->saved_context = t->sleep_interruption_context;
155	do_wakeup = true;	159	do_wakeup = true;
156	t->sleep_queue = NULL;	160	t->sleep_queue = NULL;
157	spinlock_unlock(&wq->lock);	161	spinlock_unlock(&wq->lock);
158	}	162	}
159	spinlock_unlock(&t->lock);	163	spinlock_unlock(&t->lock);
160		164
161	if (do_wakeup)	165	if (do_wakeup)
162	thread_ready(t);	166	thread_ready(t);
163		167
164	out:	168	out:
165	spinlock_unlock(&threads_lock);	169	spinlock_unlock(&threads_lock);
166	interrupts_restore(ipl);	170	interrupts_restore(ipl);
167	}	171	}
168		172
169	/** Sleep until either wakeup, timeout or interruption occurs	173	/** Sleep until either wakeup, timeout or interruption occurs
170	*	174	*
171	* This is a sleep implementation which allows itself to time out or to be	175	* This is a sleep implementation which allows itself to time out or to be
172	* interrupted from the sleep, restoring a failover context.	176	* interrupted from the sleep, restoring a failover context.
173	*	177	*
174	* Sleepers are organised in a FIFO fashion in a structure called wait queue.	178	* Sleepers are organised in a FIFO fashion in a structure called wait queue.
175	*	179	*
176	* This function is really basic in that other functions as waitq_sleep()	180	* This function is really basic in that other functions as waitq_sleep()
177	* and all the *_timeout() functions use it.	181	* and all the *_timeout() functions use it.
178	*	182	*
179	* @param wq Pointer to wait queue.	183	* @param wq Pointer to wait queue.
180	* @param usec Timeout in microseconds.	184	* @param usec Timeout in microseconds.
181	* @param flags Specify mode of the sleep.	185	* @param flags Specify mode of the sleep.
182	*	186	*
183	* The sleep can be interrupted only if the	187	* The sleep can be interrupted only if the
184	* SYNCH_FLAGS_INTERRUPTIBLE bit is specified in flags.	188	* SYNCH_FLAGS_INTERRUPTIBLE bit is specified in flags.
185		189
186	* If usec is greater than zero, regardless of the value of the	190	* If usec is greater than zero, regardless of the value of the
187	* SYNCH_FLAGS_NON_BLOCKING bit in flags, the call will not return until either timeout,	191	* SYNCH_FLAGS_NON_BLOCKING bit in flags, the call will not return until either timeout,
188	* interruption or wakeup comes.	192	* interruption or wakeup comes.
189	*	193	*
190	* If usec is zero and the SYNCH_FLAGS_NON_BLOCKING bit is not set in flags, the call	194	* If usec is zero and the SYNCH_FLAGS_NON_BLOCKING bit is not set in flags, the call
191	* will not return until wakeup or interruption comes.	195	* will not return until wakeup or interruption comes.
192	*	196	*
193	* If usec is zero and the SYNCH_FLAGS_NON_BLOCKING bit is set in flags, the call will	197	* If usec is zero and the SYNCH_FLAGS_NON_BLOCKING bit is set in flags, the call will
194	* immediately return, reporting either success or failure.	198	* immediately return, reporting either success or failure.
195	*	199	*
196	* @return Returns one of: ESYNCH_WOULD_BLOCK, ESYNCH_TIMEOUT, ESYNCH_INTERRUPTED,	200	* @return Returns one of: ESYNCH_WOULD_BLOCK, ESYNCH_TIMEOUT, ESYNCH_INTERRUPTED,
197	* ESYNCH_OK_ATOMIC, ESYNCH_OK_BLOCKED.	201	* ESYNCH_OK_ATOMIC, ESYNCH_OK_BLOCKED.
198	*	202	*
199	* @li ESYNCH_WOULD_BLOCK means that the sleep failed because at the time	203	* @li ESYNCH_WOULD_BLOCK means that the sleep failed because at the time
200	* of the call there was no pending wakeup.	204	* of the call there was no pending wakeup.
201	*	205	*
202	* @li ESYNCH_TIMEOUT means that the sleep timed out.	206	* @li ESYNCH_TIMEOUT means that the sleep timed out.
203	*	207	*
204	* @li ESYNCH_INTERRUPTED means that somebody interrupted the sleeping thread.	208	* @li ESYNCH_INTERRUPTED means that somebody interrupted the sleeping thread.
205	*	209	*
206	* @li ESYNCH_OK_ATOMIC means that the sleep succeeded and that there was	210	* @li ESYNCH_OK_ATOMIC means that the sleep succeeded and that there was
207	* a pending wakeup at the time of the call. The caller was not put	211	* a pending wakeup at the time of the call. The caller was not put
208	* asleep at all.	212	* asleep at all.
209	*	213	*
210	* @li ESYNCH_OK_BLOCKED means that the sleep succeeded; the full sleep was	214	* @li ESYNCH_OK_BLOCKED means that the sleep succeeded; the full sleep was
211	* attempted.	215	* attempted.
212	*/	216	*/
213	int waitq_sleep_timeout(waitq_t *wq, __u32 usec, int flags)	217	int waitq_sleep_timeout(waitq_t *wq, __u32 usec, int flags)
214	{	218	{
215	ipl_t ipl;	219	ipl_t ipl;
216	int rc;	220	int rc;
217		221
218	ipl = waitq_sleep_prepare(wq);	222	ipl = waitq_sleep_prepare(wq);
219	rc = waitq_sleep_timeout_unsafe(wq, usec, flags);	223	rc = waitq_sleep_timeout_unsafe(wq, usec, flags);
220	waitq_sleep_finish(wq, rc, ipl);	224	waitq_sleep_finish(wq, rc, ipl);
221	return rc;	225	return rc;
222	}	226	}
223		227
224	/** Prepare to sleep in a waitq.	228	/** Prepare to sleep in a waitq.
225	*	229	*
226	* This function will return holding the lock of the wait queue	230	* This function will return holding the lock of the wait queue
227	* and interrupts disabled.	231	* and interrupts disabled.
228	*	232	*
229	* @param wq Wait queue.	233	* @param wq Wait queue.
230	*	234	*
231	* @return Interrupt level as it existed on entry to this function.	235	* @return Interrupt level as it existed on entry to this function.
232	*/	236	*/
233	ipl_t waitq_sleep_prepare(waitq_t *wq)	237	ipl_t waitq_sleep_prepare(waitq_t *wq)
234	{	238	{
235	ipl_t ipl;	239	ipl_t ipl;
236		240
237	restart:	241	restart:
238	ipl = interrupts_disable();	242	ipl = interrupts_disable();
239		243
240	if (THREAD) { /* needed during system initiailzation */	244	if (THREAD) { /* needed during system initiailzation */
241	/*	245	/*
242	* Busy waiting for a delayed timeout.	246	* Busy waiting for a delayed timeout.
243	* This is an important fix for the race condition between	247	* This is an important fix for the race condition between
244	* a delayed timeout and a next call to waitq_sleep_timeout().	248	* a delayed timeout and a next call to waitq_sleep_timeout().
245	* Simply, the thread is not allowed to go to sleep if	249	* Simply, the thread is not allowed to go to sleep if
246	* there are timeouts in progress.	250	* there are timeouts in progress.
247	*/	251	*/
248	spinlock_lock(&THREAD->lock);	252	spinlock_lock(&THREAD->lock);
249	if (THREAD->timeout_pending) {	253	if (THREAD->timeout_pending) {
250	spinlock_unlock(&THREAD->lock);	254	spinlock_unlock(&THREAD->lock);
251	interrupts_restore(ipl);	255	interrupts_restore(ipl);
252	goto restart;	256	goto restart;
253	}	257	}
254	spinlock_unlock(&THREAD->lock);	258	spinlock_unlock(&THREAD->lock);
255	}	259	}
256		260
257	spinlock_lock(&wq->lock);	261	spinlock_lock(&wq->lock);
258	return ipl;	262	return ipl;
259	}	263	}
260		264
261	/** Finish waiting in a wait queue.	265	/** Finish waiting in a wait queue.
262	*	266	*
263	* This function restores interrupts to the state that existed prior	267	* This function restores interrupts to the state that existed prior
264	* to the call to waitq_sleep_prepare(). If necessary, the wait queue	268	* to the call to waitq_sleep_prepare(). If necessary, the wait queue
265	* lock is released.	269	* lock is released.
266	*	270	*
267	* @param wq Wait queue.	271	* @param wq Wait queue.
268	* @param rc Return code of waitq_sleep_timeout_unsafe().	272	* @param rc Return code of waitq_sleep_timeout_unsafe().
269	* @param ipl Interrupt level returned by waitq_sleep_prepare().	273	* @param ipl Interrupt level returned by waitq_sleep_prepare().
270	*/	274	*/
271	void waitq_sleep_finish(waitq_t *wq, int rc, ipl_t ipl)	275	void waitq_sleep_finish(waitq_t *wq, int rc, ipl_t ipl)
272	{	276	{
273	switch (rc) {	277	switch (rc) {
274	case ESYNCH_WOULD_BLOCK:	278	case ESYNCH_WOULD_BLOCK:
275	case ESYNCH_OK_ATOMIC:	279	case ESYNCH_OK_ATOMIC:
276	spinlock_unlock(&wq->lock);	280	spinlock_unlock(&wq->lock);
277	break;	281	break;
278	default:	282	default:
279	break;	283	break;
280	}	284	}
281	interrupts_restore(ipl);	285	interrupts_restore(ipl);
282	}	286	}
283		287
284	/** Internal implementation of waitq_sleep_timeout().	288	/** Internal implementation of waitq_sleep_timeout().
285	*	289	*
286	* This function implements logic of sleeping in a wait queue.	290	* This function implements logic of sleeping in a wait queue.
287	* This call must be preceeded by a call to waitq_sleep_prepare()	291	* This call must be preceeded by a call to waitq_sleep_prepare()
288	* and followed by a call to waitq_slee_finish().	292	* and followed by a call to waitq_slee_finish().
289	*	293	*
290	* @param wq See waitq_sleep_timeout().	294	* @param wq See waitq_sleep_timeout().
291	* @param usec See waitq_sleep_timeout().	295	* @param usec See waitq_sleep_timeout().
292	* @param flags See waitq_sleep_timeout().	296	* @param flags See waitq_sleep_timeout().
293	*	297	*
294	* @return See waitq_sleep_timeout().	298	* @return See waitq_sleep_timeout().
295	*/	299	*/
296	int waitq_sleep_timeout_unsafe(waitq_t *wq, __u32 usec, int flags)	300	int waitq_sleep_timeout_unsafe(waitq_t *wq, __u32 usec, int flags)
297	{	301	{
298	/* checks whether to go to sleep at all */	302	/* checks whether to go to sleep at all */
299	if (wq->missed_wakeups) {	303	if (wq->missed_wakeups) {
300	wq->missed_wakeups--;	304	wq->missed_wakeups--;
301	return ESYNCH_OK_ATOMIC;	305	return ESYNCH_OK_ATOMIC;
302	}	306	}
303	else {	307	else {
304	if ((flags & SYNCH_FLAGS_NON_BLOCKING) && (usec == 0)) {	308	if ((flags & SYNCH_FLAGS_NON_BLOCKING) && (usec == 0)) {
305	/* return immediatelly instead of going to sleep */	309	/* return immediatelly instead of going to sleep */
306	return ESYNCH_WOULD_BLOCK;	310	return ESYNCH_WOULD_BLOCK;
307	}	311	}
308	}	312	}
309		313
310	/*	314	/*
311	* Now we are firmly decided to go to sleep.	315	* Now we are firmly decided to go to sleep.
312	*/	316	*/
313	spinlock_lock(&THREAD->lock);	317	spinlock_lock(&THREAD->lock);
314		318
315	if (flags & SYNCH_FLAGS_INTERRUPTIBLE) {	319	if (flags & SYNCH_FLAGS_INTERRUPTIBLE) {
316		320
317	/*	321	/*
318	* If the thread was already interrupted,	322	* If the thread was already interrupted,
319	* don't go to sleep at all.	323	* don't go to sleep at all.
320	*/	324	*/
321	if (THREAD->interrupted) {	325	if (THREAD->interrupted) {
322	spinlock_unlock(&THREAD->lock);	326	spinlock_unlock(&THREAD->lock);
323	spinlock_unlock(&wq->lock);	327	spinlock_unlock(&wq->lock);
324	return ESYNCH_INTERRUPTED;	328	return ESYNCH_INTERRUPTED;
325	}	329	}
326		330
327	/*	331	/*
328	* Set context that will be restored if the sleep	332	* Set context that will be restored if the sleep
329	* of this thread is ever interrupted.	333	* of this thread is ever interrupted.
330	*/	334	*/
331	THREAD->sleep_interruptible = true;	335	THREAD->sleep_interruptible = true;
332	if (!context_save(&THREAD->sleep_interruption_context)) {	336	if (!context_save(&THREAD->sleep_interruption_context)) {
333	/* Short emulation of scheduler() return code. */	337	/* Short emulation of scheduler() return code. */
334	spinlock_unlock(&THREAD->lock);	338	spinlock_unlock(&THREAD->lock);
335	return ESYNCH_INTERRUPTED;	339	return ESYNCH_INTERRUPTED;
336	}	340	}
337		341
338	} else {	342	} else {
339	THREAD->sleep_interruptible = false;	343	THREAD->sleep_interruptible = false;
340	}	344	}
341		345
342	if (usec) {	346	if (usec) {
343	/* We use the timeout variant. */	347	/* We use the timeout variant. */
344	if (!context_save(&THREAD->sleep_timeout_context)) {	348	if (!context_save(&THREAD->sleep_timeout_context)) {
345	/* Short emulation of scheduler() return code. */	349	/* Short emulation of scheduler() return code. */
346	spinlock_unlock(&THREAD->lock);	350	spinlock_unlock(&THREAD->lock);
347	return ESYNCH_TIMEOUT;	351	return ESYNCH_TIMEOUT;
348	}	352	}
349	THREAD->timeout_pending = true;	353	THREAD->timeout_pending = true;
350	timeout_register(&THREAD->sleep_timeout, (__u64) usec, waitq_timeouted_sleep, THREAD);	354	timeout_register(&THREAD->sleep_timeout, (__u64) usec, waitq_timeouted_sleep, THREAD);
351	}	355	}
352		356
353	list_append(&THREAD->wq_link, &wq->head);	357	list_append(&THREAD->wq_link, &wq->head);
354		358
355	/*	359	/*
356	* Suspend execution.	360	* Suspend execution.
357	*/	361	*/
358	THREAD->state = Sleeping;	362	THREAD->state = Sleeping;
359	THREAD->sleep_queue = wq;	363	THREAD->sleep_queue = wq;
360		364
361	spinlock_unlock(&THREAD->lock);	365	spinlock_unlock(&THREAD->lock);
362		366
363	scheduler(); /* wq->lock is released in scheduler_separated_stack() */	367	scheduler(); /* wq->lock is released in scheduler_separated_stack() */
364		368
365	return ESYNCH_OK_BLOCKED;	369	return ESYNCH_OK_BLOCKED;
366	}	370	}
367		371
368		372
369	/** Wake up first thread sleeping in a wait queue	373	/** Wake up first thread sleeping in a wait queue
370	*	374	*
371	* Wake up first thread sleeping in a wait queue.	375	* Wake up first thread sleeping in a wait queue.
372	* This is the SMP- and IRQ-safe wrapper meant for	376	* This is the SMP- and IRQ-safe wrapper meant for
373	* general use.	377	* general use.
374	*	378	*
375	* Besides its 'normal' wakeup operation, it attempts	379	* Besides its 'normal' wakeup operation, it attempts
376	* to unregister possible timeout.	380	* to unregister possible timeout.
377	*	381	*
378	* @param wq Pointer to wait queue.	382	* @param wq Pointer to wait queue.
379	* @param all If this is non-zero, all sleeping threads	383	* @param all If this is non-zero, all sleeping threads
380	* will be woken up and missed count will be zeroed.	384	* will be woken up and missed count will be zeroed.
381	*/	385	*/
382	void waitq_wakeup(waitq_t *wq, bool all)	386	void waitq_wakeup(waitq_t *wq, bool all)
383	{	387	{
384	ipl_t ipl;	388	ipl_t ipl;
385		389
386	ipl = interrupts_disable();	390	ipl = interrupts_disable();
387	spinlock_lock(&wq->lock);	391	spinlock_lock(&wq->lock);
388		392
389	_waitq_wakeup_unsafe(wq, all);	393	_waitq_wakeup_unsafe(wq, all);
390		394
391	spinlock_unlock(&wq->lock);	395	spinlock_unlock(&wq->lock);
392	interrupts_restore(ipl);	396	interrupts_restore(ipl);
393	}	397	}
394		398
395	/** Internal SMP- and IRQ-unsafe version of waitq_wakeup()	399	/** Internal SMP- and IRQ-unsafe version of waitq_wakeup()
396	*	400	*
397	* This is the internal SMP- and IRQ-unsafe version	401	* This is the internal SMP- and IRQ-unsafe version
398	* of waitq_wakeup(). It assumes wq->lock is already	402	* of waitq_wakeup(). It assumes wq->lock is already
399	* locked and interrupts are already disabled.	403	* locked and interrupts are already disabled.
400	*	404	*
401	* @param wq Pointer to wait queue.	405	* @param wq Pointer to wait queue.
402	* @param all If this is non-zero, all sleeping threads	406	* @param all If this is non-zero, all sleeping threads
403	* will be woken up and missed count will be zeroed.	407	* will be woken up and missed count will be zeroed.
404	*/	408	*/
405	void _waitq_wakeup_unsafe(waitq_t *wq, bool all)	409	void _waitq_wakeup_unsafe(waitq_t *wq, bool all)
406	{	410	{
407	thread_t *t;	411	thread_t *t;
408		412
409	loop:	413	loop:
410	if (list_empty(&wq->head)) {	414	if (list_empty(&wq->head)) {
411	wq->missed_wakeups++;	415	wq->missed_wakeups++;
412	if (all)	416	if (all)
413	wq->missed_wakeups = 0;	417	wq->missed_wakeups = 0;
414	return;	418	return;
415	}	419	}
416		420
417	t = list_get_instance(wq->head.next, thread_t, wq_link);	421	t = list_get_instance(wq->head.next, thread_t, wq_link);
418		422
419	/*	423	/*
420	* Lock the thread prior to removing it from the wq.	424	* Lock the thread prior to removing it from the wq.
421	* This is not necessary because of mutual exclusion	425	* This is not necessary because of mutual exclusion
422	* (the link belongs to the wait queue), but because	426	* (the link belongs to the wait queue), but because
423	* of synchronization with waitq_timeouted_sleep()	427	* of synchronization with waitq_timeouted_sleep()
424	* and waitq_interrupt_sleep().	428	* and waitq_interrupt_sleep().
425	*	429	*
426	* In order for these two functions to work, the following	430	* In order for these two functions to work, the following
427	* invariant must hold:	431	* invariant must hold:
428	*	432	*
429	* t->sleep_queue != NULL <=> t sleeps in a wait queue	433	* t->sleep_queue != NULL <=> t sleeps in a wait queue
430	*	434	*
431	* For an observer who locks the thread, the invariant	435	* For an observer who locks the thread, the invariant
432	* holds only when the lock is held prior to removing	436	* holds only when the lock is held prior to removing
433	* it from the wait queue.	437	* it from the wait queue.
434	*/	438	*/
435	spinlock_lock(&t->lock);	439	spinlock_lock(&t->lock);
436	list_remove(&t->wq_link);	440	list_remove(&t->wq_link);
437		441
438	if (t->timeout_pending && timeout_unregister(&t->sleep_timeout))	442	if (t->timeout_pending && timeout_unregister(&t->sleep_timeout))
439	t->timeout_pending = false;	443	t->timeout_pending = false;
440	t->sleep_queue = NULL;	444	t->sleep_queue = NULL;
441	spinlock_unlock(&t->lock);	445	spinlock_unlock(&t->lock);
442		446
443	thread_ready(t);	447	thread_ready(t);
444		448
445	if (all)	449	if (all)
446	goto loop;	450	goto loop;
447	}	451	}
-		452
-		453	/** @}
-		454	*/
-		455
448		456

Subversion Repositories HelenOS-historic

(root)/kernel/trunk/generic/src/synch/waitq.c – Rev 1681 → 1702