WebSVN – HelenOS – Diff – /tags/0.2.0.1/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.
 */
 
/**
 * @file    waitq.c
 * @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 1965	Rev 1968
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	/**	29	/**
30	* @file waitq.c	30	* @file waitq.c
31	* @brief Wait queue.	31	* @brief Wait queue.
32	*	32	*
33	* Wait queue is the basic synchronization primitive upon which all	33	* Wait queue is the basic synchronization primitive upon which all
34	* other synchronization primitives build.	34	* other synchronization primitives build.
35	*	35	*
36	* It allows threads to wait for an event in first-come, first-served	36	* It allows threads to wait for an event in first-come, first-served
37	* fashion. Conditional operation as well as timeouts and interruptions	37	* fashion. Conditional operation as well as timeouts and interruptions
38	* are supported.	38	* are supported.
39	*/	39	*/
40		40
41	#include <synch/waitq.h>	41	#include <synch/waitq.h>
42	#include <synch/synch.h>	42	#include <synch/synch.h>
43	#include <synch/spinlock.h>	43	#include <synch/spinlock.h>
44	#include <proc/thread.h>	44	#include <proc/thread.h>
45	#include <proc/scheduler.h>	45	#include <proc/scheduler.h>
46	#include <arch/asm.h>	46	#include <arch/asm.h>
47	#include <arch/types.h>	47	#include <arch/types.h>
48	#include <typedefs.h>	48	#include <typedefs.h>
49	#include <time/timeout.h>	49	#include <time/timeout.h>
50	#include <arch.h>	50	#include <arch.h>
51	#include <context.h>	51	#include <context.h>
52	#include <adt/list.h>	52	#include <adt/list.h>
53		53
54	static void waitq_timeouted_sleep(void *data);	54	static void waitq_timeouted_sleep(void *data);
55		55
56	/** Initialize wait queue	56	/** Initialize wait queue
57	*	57	*
58	* Initialize wait queue.	58	* Initialize wait queue.
59	*	59	*
60	* @param wq Pointer to wait queue to be initialized.	60	* @param wq Pointer to wait queue to be initialized.
61	*/	61	*/
62	void waitq_initialize(waitq_t *wq)	62	void waitq_initialize(waitq_t *wq)
63	{	63	{
64	spinlock_initialize(&wq->lock, "waitq_lock");	64	spinlock_initialize(&wq->lock, "waitq_lock");
65	list_initialize(&wq->head);	65	list_initialize(&wq->head);
66	wq->missed_wakeups = 0;	66	wq->missed_wakeups = 0;
67	}	67	}
68		68
69	/** Handle timeout during waitq_sleep_timeout() call	69	/** Handle timeout during waitq_sleep_timeout() call
70	*	70	*
71	* This routine is called when waitq_sleep_timeout() timeouts.	71	* This routine is called when waitq_sleep_timeout() timeouts.
72	* Interrupts are disabled.	72	* Interrupts are disabled.
73	*	73	*
74	* It is supposed to try to remove 'its' thread from the wait queue;	74	* 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	75	* 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	76	* overlap. In that case it behaves just as though there was no
77	* timeout at all.	77	* timeout at all.
78	*	78	*
79	* @param data Pointer to the thread that called waitq_sleep_timeout().	79	* @param data Pointer to the thread that called waitq_sleep_timeout().
80	*/	80	*/
81	void waitq_timeouted_sleep(void *data)	81	void waitq_timeouted_sleep(void *data)
82	{	82	{
83	thread_t t = (thread_t ) data;	83	thread_t t = (thread_t ) data;
84	waitq_t *wq;	84	waitq_t *wq;
85	bool do_wakeup = false;	85	bool do_wakeup = false;
86		86
87	spinlock_lock(&threads_lock);	87	spinlock_lock(&threads_lock);
88	if (!thread_exists(t))	88	if (!thread_exists(t))
89	goto out;	89	goto out;
90		90
91	grab_locks:	91	grab_locks:
92	spinlock_lock(&t->lock);	92	spinlock_lock(&t->lock);
93	if ((wq = t->sleep_queue)) { /* assignment */	93	if ((wq = t->sleep_queue)) { /* assignment */
94	if (!spinlock_trylock(&wq->lock)) {	94	if (!spinlock_trylock(&wq->lock)) {
95	spinlock_unlock(&t->lock);	95	spinlock_unlock(&t->lock);
96	goto grab_locks; /* avoid deadlock */	96	goto grab_locks; /* avoid deadlock */
97	}	97	}
98		98
99	list_remove(&t->wq_link);	99	list_remove(&t->wq_link);
100	t->saved_context = t->sleep_timeout_context;	100	t->saved_context = t->sleep_timeout_context;
101	do_wakeup = true;	101	do_wakeup = true;
102	t->sleep_queue = NULL;	102	t->sleep_queue = NULL;
103	spinlock_unlock(&wq->lock);	103	spinlock_unlock(&wq->lock);
104	}	104	}
105		105
106	t->timeout_pending = false;	106	t->timeout_pending = false;
107	spinlock_unlock(&t->lock);	107	spinlock_unlock(&t->lock);
108		108
109	if (do_wakeup)	109	if (do_wakeup)
110	thread_ready(t);	110	thread_ready(t);
111		111
112	out:	112	out:
113	spinlock_unlock(&threads_lock);	113	spinlock_unlock(&threads_lock);
114	}	114	}
115		115
116	/** Interrupt sleeping thread.	116	/** Interrupt sleeping thread.
117	*	117	*
118	* This routine attempts to interrupt a thread from its sleep in a waitqueue.	118	* 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.	119	* If the thread is not found sleeping, no action is taken.
120	*	120	*
121	* @param t Thread to be interrupted.	121	* @param t Thread to be interrupted.
122	*/	122	*/
123	void waitq_interrupt_sleep(thread_t *t)	123	void waitq_interrupt_sleep(thread_t *t)
124	{	124	{
125	waitq_t *wq;	125	waitq_t *wq;
126	bool do_wakeup = false;	126	bool do_wakeup = false;
127	ipl_t ipl;	127	ipl_t ipl;
128		128
129	ipl = interrupts_disable();	129	ipl = interrupts_disable();
130	spinlock_lock(&threads_lock);	130	spinlock_lock(&threads_lock);
131	if (!thread_exists(t))	131	if (!thread_exists(t))
132	goto out;	132	goto out;
133		133
134	grab_locks:	134	grab_locks:
135	spinlock_lock(&t->lock);	135	spinlock_lock(&t->lock);
136	if ((wq = t->sleep_queue)) { /* assignment */	136	if ((wq = t->sleep_queue)) { /* assignment */
137	if (!(t->sleep_interruptible)) {	137	if (!(t->sleep_interruptible)) {
138	/*	138	/*
139	* The sleep cannot be interrupted.	139	* The sleep cannot be interrupted.
140	*/	140	*/
141	spinlock_unlock(&t->lock);	141	spinlock_unlock(&t->lock);
142	goto out;	142	goto out;
143	}	143	}
144		144
145	if (!spinlock_trylock(&wq->lock)) {	145	if (!spinlock_trylock(&wq->lock)) {
146	spinlock_unlock(&t->lock);	146	spinlock_unlock(&t->lock);
147	goto grab_locks; /* avoid deadlock */	147	goto grab_locks; /* avoid deadlock */
148	}	148	}
149		149
150	if (t->timeout_pending && timeout_unregister(&t->sleep_timeout))	150	if (t->timeout_pending && timeout_unregister(&t->sleep_timeout))
151	t->timeout_pending = false;	151	t->timeout_pending = false;
152		152
153	list_remove(&t->wq_link);	153	list_remove(&t->wq_link);
154	t->saved_context = t->sleep_interruption_context;	154	t->saved_context = t->sleep_interruption_context;
155	do_wakeup = true;	155	do_wakeup = true;
156	t->sleep_queue = NULL;	156	t->sleep_queue = NULL;
157	spinlock_unlock(&wq->lock);	157	spinlock_unlock(&wq->lock);
158	}	158	}
159	spinlock_unlock(&t->lock);	159	spinlock_unlock(&t->lock);
160		160
161	if (do_wakeup)	161	if (do_wakeup)
162	thread_ready(t);	162	thread_ready(t);
163		163
164	out:	164	out:
165	spinlock_unlock(&threads_lock);	165	spinlock_unlock(&threads_lock);
166	interrupts_restore(ipl);	166	interrupts_restore(ipl);
167	}	167	}
168		168
169	/** Sleep until either wakeup, timeout or interruption occurs	169	/** Sleep until either wakeup, timeout or interruption occurs
170	*	170	*
171	* This is a sleep implementation which allows itself to time out or to be	171	* This is a sleep implementation which allows itself to time out or to be
172	* interrupted from the sleep, restoring a failover context.	172	* interrupted from the sleep, restoring a failover context.
173	*	173	*
174	* Sleepers are organised in a FIFO fashion in a structure called wait queue.	174	* Sleepers are organised in a FIFO fashion in a structure called wait queue.
175	*	175	*
176	* This function is really basic in that other functions as waitq_sleep()	176	* This function is really basic in that other functions as waitq_sleep()
177	* and all the *_timeout() functions use it.	177	* and all the *_timeout() functions use it.
178	*	178	*
179	* @param wq Pointer to wait queue.	179	* @param wq Pointer to wait queue.
180	* @param usec Timeout in microseconds.	180	* @param usec Timeout in microseconds.
181	* @param flags Specify mode of the sleep.	181	* @param flags Specify mode of the sleep.
182	*	182	*
183	* The sleep can be interrupted only if the	183	* The sleep can be interrupted only if the
184	* SYNCH_FLAGS_INTERRUPTIBLE bit is specified in flags.	184	* SYNCH_FLAGS_INTERRUPTIBLE bit is specified in flags.
185		185
186	* If usec is greater than zero, regardless of the value of the	186	* 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,	187	* SYNCH_FLAGS_NON_BLOCKING bit in flags, the call will not return until either timeout,
188	* interruption or wakeup comes.	188	* interruption or wakeup comes.
189	*	189	*
190	* If usec is zero and the SYNCH_FLAGS_NON_BLOCKING bit is not set in flags, the call	190	* 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.	191	* will not return until wakeup or interruption comes.
192	*	192	*
193	* If usec is zero and the SYNCH_FLAGS_NON_BLOCKING bit is set in flags, the call will	193	* 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.	194	* immediately return, reporting either success or failure.
195	*	195	*
196	* @return Returns one of: ESYNCH_WOULD_BLOCK, ESYNCH_TIMEOUT, ESYNCH_INTERRUPTED,	196	* @return Returns one of: ESYNCH_WOULD_BLOCK, ESYNCH_TIMEOUT, ESYNCH_INTERRUPTED,
197	* ESYNCH_OK_ATOMIC, ESYNCH_OK_BLOCKED.	197	* ESYNCH_OK_ATOMIC, ESYNCH_OK_BLOCKED.
198	*	198	*
199	* @li ESYNCH_WOULD_BLOCK means that the sleep failed because at the time	199	* @li ESYNCH_WOULD_BLOCK means that the sleep failed because at the time
200	* of the call there was no pending wakeup.	200	* of the call there was no pending wakeup.
201	*	201	*
202	* @li ESYNCH_TIMEOUT means that the sleep timed out.	202	* @li ESYNCH_TIMEOUT means that the sleep timed out.
203	*	203	*
204	* @li ESYNCH_INTERRUPTED means that somebody interrupted the sleeping thread.	204	* @li ESYNCH_INTERRUPTED means that somebody interrupted the sleeping thread.
205	*	205	*
206	* @li ESYNCH_OK_ATOMIC means that the sleep succeeded and that there was	206	* @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	207	* a pending wakeup at the time of the call. The caller was not put
208	* asleep at all.	208	* asleep at all.
209	*	209	*
210	* @li ESYNCH_OK_BLOCKED means that the sleep succeeded; the full sleep was	210	* @li ESYNCH_OK_BLOCKED means that the sleep succeeded; the full sleep was
211	* attempted.	211	* attempted.
212	*/	212	*/
213	int waitq_sleep_timeout(waitq_t *wq, __u32 usec, int flags)	213	int waitq_sleep_timeout(waitq_t *wq, __u32 usec, int flags)
214	{	214	{
215	ipl_t ipl;	215	ipl_t ipl;
216	int rc;	216	int rc;
217		217
218	ipl = waitq_sleep_prepare(wq);	218	ipl = waitq_sleep_prepare(wq);
219	rc = waitq_sleep_timeout_unsafe(wq, usec, flags);	219	rc = waitq_sleep_timeout_unsafe(wq, usec, flags);
220	waitq_sleep_finish(wq, rc, ipl);	220	waitq_sleep_finish(wq, rc, ipl);
221	return rc;	221	return rc;
222	}	222	}
223		223
224	/** Prepare to sleep in a waitq.	224	/** Prepare to sleep in a waitq.
225	*	225	*
226	* This function will return holding the lock of the wait queue	226	* This function will return holding the lock of the wait queue
227	* and interrupts disabled.	227	* and interrupts disabled.
228	*	228	*
229	* @param wq Wait queue.	229	* @param wq Wait queue.
230	*	230	*
231	* @return Interrupt level as it existed on entry to this function.	231	* @return Interrupt level as it existed on entry to this function.
232	*/	232	*/
233	ipl_t waitq_sleep_prepare(waitq_t *wq)	233	ipl_t waitq_sleep_prepare(waitq_t *wq)
234	{	234	{
235	ipl_t ipl;	235	ipl_t ipl;
236		236
237	restart:	237	restart:
238	ipl = interrupts_disable();	238	ipl = interrupts_disable();
239		239
240	if (THREAD) { /* needed during system initiailzation */	240	if (THREAD) { /* needed during system initiailzation */
241	/*	241	/*
242	* Busy waiting for a delayed timeout.	242	* Busy waiting for a delayed timeout.
243	* This is an important fix for the race condition between	243	* This is an important fix for the race condition between
244	* a delayed timeout and a next call to waitq_sleep_timeout().	244	* a delayed timeout and a next call to waitq_sleep_timeout().
245	* Simply, the thread is not allowed to go to sleep if	245	* Simply, the thread is not allowed to go to sleep if
246	* there are timeouts in progress.	246	* there are timeouts in progress.
247	*/	247	*/
248	spinlock_lock(&THREAD->lock);	248	spinlock_lock(&THREAD->lock);
249	if (THREAD->timeout_pending) {	249	if (THREAD->timeout_pending) {
250	spinlock_unlock(&THREAD->lock);	250	spinlock_unlock(&THREAD->lock);
251	interrupts_restore(ipl);	251	interrupts_restore(ipl);
252	goto restart;	252	goto restart;
253	}	253	}
254	spinlock_unlock(&THREAD->lock);	254	spinlock_unlock(&THREAD->lock);
255	}	255	}
256		256
257	spinlock_lock(&wq->lock);	257	spinlock_lock(&wq->lock);
258	return ipl;	258	return ipl;
259	}	259	}
260		260
261	/** Finish waiting in a wait queue.	261	/** Finish waiting in a wait queue.
262	*	262	*
263	* This function restores interrupts to the state that existed prior	263	* This function restores interrupts to the state that existed prior
264	* to the call to waitq_sleep_prepare(). If necessary, the wait queue	264	* to the call to waitq_sleep_prepare(). If necessary, the wait queue
265	* lock is released.	265	* lock is released.
266	*	266	*
267	* @param wq Wait queue.	267	* @param wq Wait queue.
268	* @param rc Return code of waitq_sleep_timeout_unsafe().	268	* @param rc Return code of waitq_sleep_timeout_unsafe().
269	* @param ipl Interrupt level returned by waitq_sleep_prepare().	269	* @param ipl Interrupt level returned by waitq_sleep_prepare().
270	*/	270	*/
271	void waitq_sleep_finish(waitq_t *wq, int rc, ipl_t ipl)	271	void waitq_sleep_finish(waitq_t *wq, int rc, ipl_t ipl)
272	{	272	{
273	switch (rc) {	273	switch (rc) {
274	case ESYNCH_WOULD_BLOCK:	274	case ESYNCH_WOULD_BLOCK:
275	case ESYNCH_OK_ATOMIC:	275	case ESYNCH_OK_ATOMIC:
276	spinlock_unlock(&wq->lock);	276	spinlock_unlock(&wq->lock);
277	break;	277	break;
278	default:	278	default:
279	break;	279	break;
280	}	280	}
281	interrupts_restore(ipl);	281	interrupts_restore(ipl);
282	}	282	}
283		283
284	/** Internal implementation of waitq_sleep_timeout().	284	/** Internal implementation of waitq_sleep_timeout().
285	*	285	*
286	* This function implements logic of sleeping in a wait queue.	286	* This function implements logic of sleeping in a wait queue.
287	* This call must be preceeded by a call to waitq_sleep_prepare()	287	* This call must be preceeded by a call to waitq_sleep_prepare()
288	* and followed by a call to waitq_slee_finish().	288	* and followed by a call to waitq_slee_finish().
289	*	289	*
290	* @param wq See waitq_sleep_timeout().	290	* @param wq See waitq_sleep_timeout().
291	* @param usec See waitq_sleep_timeout().	291	* @param usec See waitq_sleep_timeout().
292	* @param flags See waitq_sleep_timeout().	292	* @param flags See waitq_sleep_timeout().
293	*	293	*
294	* @return See waitq_sleep_timeout().	294	* @return See waitq_sleep_timeout().
295	*/	295	*/
296	int waitq_sleep_timeout_unsafe(waitq_t *wq, __u32 usec, int flags)	296	int waitq_sleep_timeout_unsafe(waitq_t *wq, __u32 usec, int flags)
297	{	297	{
298	/* checks whether to go to sleep at all */	298	/* checks whether to go to sleep at all */
299	if (wq->missed_wakeups) {	299	if (wq->missed_wakeups) {
300	wq->missed_wakeups--;	300	wq->missed_wakeups--;
301	return ESYNCH_OK_ATOMIC;	301	return ESYNCH_OK_ATOMIC;
302	}	302	}
303	else {	303	else {
304	if ((flags & SYNCH_FLAGS_NON_BLOCKING) && (usec == 0)) {	304	if ((flags & SYNCH_FLAGS_NON_BLOCKING) && (usec == 0)) {
305	/* return immediatelly instead of going to sleep */	305	/* return immediatelly instead of going to sleep */
306	return ESYNCH_WOULD_BLOCK;	306	return ESYNCH_WOULD_BLOCK;
307	}	307	}
308	}	308	}
309		309
310	/*	310	/*
311	* Now we are firmly decided to go to sleep.	311	* Now we are firmly decided to go to sleep.
312	*/	312	*/
313	spinlock_lock(&THREAD->lock);	313	spinlock_lock(&THREAD->lock);
314		314
315	if (flags & SYNCH_FLAGS_INTERRUPTIBLE) {	315	if (flags & SYNCH_FLAGS_INTERRUPTIBLE) {
316		316
317	/*	317	/*
318	* If the thread was already interrupted,	318	* If the thread was already interrupted,
319	* don't go to sleep at all.	319	* don't go to sleep at all.
320	*/	320	*/
321	if (THREAD->interrupted) {	321	if (THREAD->interrupted) {
322	spinlock_unlock(&THREAD->lock);	322	spinlock_unlock(&THREAD->lock);
323	spinlock_unlock(&wq->lock);	323	spinlock_unlock(&wq->lock);
324	return ESYNCH_INTERRUPTED;	324	return ESYNCH_INTERRUPTED;
325	}	325	}
326		326
327	/*	327	/*
328	* Set context that will be restored if the sleep	328	* Set context that will be restored if the sleep
329	* of this thread is ever interrupted.	329	* of this thread is ever interrupted.
330	*/	330	*/
331	THREAD->sleep_interruptible = true;	331	THREAD->sleep_interruptible = true;
332	if (!context_save(&THREAD->sleep_interruption_context)) {	332	if (!context_save(&THREAD->sleep_interruption_context)) {
333	/* Short emulation of scheduler() return code. */	333	/* Short emulation of scheduler() return code. */
334	spinlock_unlock(&THREAD->lock);	334	spinlock_unlock(&THREAD->lock);
335	return ESYNCH_INTERRUPTED;	335	return ESYNCH_INTERRUPTED;
336	}	336	}
337		337
338	} else {	338	} else {
339	THREAD->sleep_interruptible = false;	339	THREAD->sleep_interruptible = false;
340	}	340	}
341		341
342	if (usec) {	342	if (usec) {
343	/* We use the timeout variant. */	343	/* We use the timeout variant. */
344	if (!context_save(&THREAD->sleep_timeout_context)) {	344	if (!context_save(&THREAD->sleep_timeout_context)) {
345	/* Short emulation of scheduler() return code. */	345	/* Short emulation of scheduler() return code. */
346	spinlock_unlock(&THREAD->lock);	346	spinlock_unlock(&THREAD->lock);
347	return ESYNCH_TIMEOUT;	347	return ESYNCH_TIMEOUT;
348	}	348	}
349	THREAD->timeout_pending = true;	349	THREAD->timeout_pending = true;
350	timeout_register(&THREAD->sleep_timeout, (__u64) usec, waitq_timeouted_sleep, THREAD);	350	timeout_register(&THREAD->sleep_timeout, (__u64) usec, waitq_timeouted_sleep, THREAD);
351	}	351	}
352		352
353	list_append(&THREAD->wq_link, &wq->head);	353	list_append(&THREAD->wq_link, &wq->head);
354		354
355	/*	355	/*
356	* Suspend execution.	356	* Suspend execution.
357	*/	357	*/
358	THREAD->state = Sleeping;	358	THREAD->state = Sleeping;
359	THREAD->sleep_queue = wq;	359	THREAD->sleep_queue = wq;
360		360
361	spinlock_unlock(&THREAD->lock);	361	spinlock_unlock(&THREAD->lock);
362		362
363	scheduler(); /* wq->lock is released in scheduler_separated_stack() */	363	scheduler(); /* wq->lock is released in scheduler_separated_stack() */
364		364
365	return ESYNCH_OK_BLOCKED;	365	return ESYNCH_OK_BLOCKED;
366	}	366	}
367		367
368		368
369	/** Wake up first thread sleeping in a wait queue	369	/** Wake up first thread sleeping in a wait queue
370	*	370	*
371	* Wake up first thread sleeping in a wait queue.	371	* Wake up first thread sleeping in a wait queue.
372	* This is the SMP- and IRQ-safe wrapper meant for	372	* This is the SMP- and IRQ-safe wrapper meant for
373	* general use.	373	* general use.
374	*	374	*
375	* Besides its 'normal' wakeup operation, it attempts	375	* Besides its 'normal' wakeup operation, it attempts
376	* to unregister possible timeout.	376	* to unregister possible timeout.
377	*	377	*
378	* @param wq Pointer to wait queue.	378	* @param wq Pointer to wait queue.
379	* @param all If this is non-zero, all sleeping threads	379	* @param all If this is non-zero, all sleeping threads
380	* will be woken up and missed count will be zeroed.	380	* will be woken up and missed count will be zeroed.
381	*/	381	*/
382	void waitq_wakeup(waitq_t *wq, bool all)	382	void waitq_wakeup(waitq_t *wq, bool all)
383	{	383	{
384	ipl_t ipl;	384	ipl_t ipl;
385		385
386	ipl = interrupts_disable();	386	ipl = interrupts_disable();
387	spinlock_lock(&wq->lock);	387	spinlock_lock(&wq->lock);
388		388
389	_waitq_wakeup_unsafe(wq, all);	389	_waitq_wakeup_unsafe(wq, all);
390		390
391	spinlock_unlock(&wq->lock);	391	spinlock_unlock(&wq->lock);
392	interrupts_restore(ipl);	392	interrupts_restore(ipl);
393	}	393	}
394		394
395	/** Internal SMP- and IRQ-unsafe version of waitq_wakeup()	395	/** Internal SMP- and IRQ-unsafe version of waitq_wakeup()
396	*	396	*
397	* This is the internal SMP- and IRQ-unsafe version	397	* This is the internal SMP- and IRQ-unsafe version
398	* of waitq_wakeup(). It assumes wq->lock is already	398	* of waitq_wakeup(). It assumes wq->lock is already
399	* locked and interrupts are already disabled.	399	* locked and interrupts are already disabled.
400	*	400	*
401	* @param wq Pointer to wait queue.	401	* @param wq Pointer to wait queue.
402	* @param all If this is non-zero, all sleeping threads	402	* @param all If this is non-zero, all sleeping threads
403	* will be woken up and missed count will be zeroed.	403	* will be woken up and missed count will be zeroed.
404	*/	404	*/
405	void _waitq_wakeup_unsafe(waitq_t *wq, bool all)	405	void _waitq_wakeup_unsafe(waitq_t *wq, bool all)
406	{	406	{
407	thread_t *t;	407	thread_t *t;
408		408
409	loop:	409	loop:
410	if (list_empty(&wq->head)) {	410	if (list_empty(&wq->head)) {
411	wq->missed_wakeups++;	411	wq->missed_wakeups++;
412	if (all)	412	if (all)
413	wq->missed_wakeups = 0;	413	wq->missed_wakeups = 0;
414	return;	414	return;
415	}	415	}
416		416
417	t = list_get_instance(wq->head.next, thread_t, wq_link);	417	t = list_get_instance(wq->head.next, thread_t, wq_link);
418		418
419	/*	419	/*
420	* Lock the thread prior to removing it from the wq.	420	* Lock the thread prior to removing it from the wq.
421	* This is not necessary because of mutual exclusion	421	* This is not necessary because of mutual exclusion
422	* (the link belongs to the wait queue), but because	422	* (the link belongs to the wait queue), but because
423	* of synchronization with waitq_timeouted_sleep()	423	* of synchronization with waitq_timeouted_sleep()
424	* and waitq_interrupt_sleep().	424	* and waitq_interrupt_sleep().
425	*	425	*
426	* In order for these two functions to work, the following	426	* In order for these two functions to work, the following
427	* invariant must hold:	427	* invariant must hold:
428	*	428	*
429	* t->sleep_queue != NULL <=> t sleeps in a wait queue	429	* t->sleep_queue != NULL <=> t sleeps in a wait queue
430	*	430	*
431	* For an observer who locks the thread, the invariant	431	* For an observer who locks the thread, the invariant
432	* holds only when the lock is held prior to removing	432	* holds only when the lock is held prior to removing
433	* it from the wait queue.	433	* it from the wait queue.
434	*/	434	*/
435	spinlock_lock(&t->lock);	435	spinlock_lock(&t->lock);
436	list_remove(&t->wq_link);	436	list_remove(&t->wq_link);
437		437
438	if (t->timeout_pending && timeout_unregister(&t->sleep_timeout))	438	if (t->timeout_pending && timeout_unregister(&t->sleep_timeout))
439	t->timeout_pending = false;	439	t->timeout_pending = false;
440	t->sleep_queue = NULL;	440	t->sleep_queue = NULL;
441	spinlock_unlock(&t->lock);	441	spinlock_unlock(&t->lock);
442		442
443	thread_ready(t);	443	thread_ready(t);
444		444
445	if (all)	445	if (all)
446	goto loop;	446	goto loop;
447	}	447	}
448		448

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(root)/tags/0.2.0.1/kernel/generic/src/synch/waitq.c – Rev 1965 → 1968