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.
 */
 
/**
 * @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;
       
        spinlock_unlock(&wq->lock);
        t->sleep_queue = NULL;
    }
   
    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 */
        }
 
        list_remove(&t->wq_link);
        t->saved_context = t->sleep_interruption_context;
        do_wakeup = true;
       
        spinlock_unlock(&wq->lock);
        t->sleep_queue = NULL;
    }
    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) {
        /*
         * 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);
   
    list_remove(&t->wq_link);
    spinlock_lock(&t->lock);
    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 1467	Rev 1502
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		102
103	spinlock_unlock(&wq->lock);	103	spinlock_unlock(&wq->lock);
104	t->sleep_queue = NULL;	104	t->sleep_queue = NULL;
105	}	105	}
106		106
107	t->timeout_pending = false;	107	t->timeout_pending = false;
108	spinlock_unlock(&t->lock);	108	spinlock_unlock(&t->lock);
109		109
110	if (do_wakeup)	110	if (do_wakeup)
111	thread_ready(t);	111	thread_ready(t);
112		112
113	out:	113	out:
114	spinlock_unlock(&threads_lock);	114	spinlock_unlock(&threads_lock);
115	}	115	}
116		116
117	/** Interrupt sleeping thread.	117	/** Interrupt sleeping thread.
118	*	118	*
119	* This routine attempts to interrupt a thread from its sleep in a waitqueue.	119	* This routine attempts to interrupt a thread from its sleep in a waitqueue.
120	* If the thread is not found sleeping, no action is taken.	120	* If the thread is not found sleeping, no action is taken.
121	*	121	*
122	* @param t Thread to be interrupted.	122	* @param t Thread to be interrupted.
123	*/	123	*/
124	void waitq_interrupt_sleep(thread_t *t)	124	void waitq_interrupt_sleep(thread_t *t)
125	{	125	{
126	waitq_t *wq;	126	waitq_t *wq;
127	bool do_wakeup = false;	127	bool do_wakeup = false;
128	ipl_t ipl;	128	ipl_t ipl;
129		129
130	ipl = interrupts_disable();	130	ipl = interrupts_disable();
131	spinlock_lock(&threads_lock);	131	spinlock_lock(&threads_lock);
132	if (!thread_exists(t))	132	if (!thread_exists(t))
133	goto out;	133	goto out;
134		134
135	grab_locks:	135	grab_locks:
136	spinlock_lock(&t->lock);	136	spinlock_lock(&t->lock);
137	if ((wq = t->sleep_queue)) { /* assignment */	137	if ((wq = t->sleep_queue)) { /* assignment */
-		138	if (!(t->sleep_interruptible)) {
-		139	/*
-		140	* The sleep cannot be interrupted.
-		141	*/
-		142	spinlock_unlock(&t->lock);
-		143	goto out;
-		144	}
-		145
138	if (!spinlock_trylock(&wq->lock)) {	146	if (!spinlock_trylock(&wq->lock)) {
139	spinlock_unlock(&t->lock);	147	spinlock_unlock(&t->lock);
140	goto grab_locks; /* avoid deadlock */	148	goto grab_locks; /* avoid deadlock */
141	}	149	}
142		150
143	list_remove(&t->wq_link);	151	list_remove(&t->wq_link);
144	t->saved_context = t->sleep_interruption_context;	152	t->saved_context = t->sleep_interruption_context;
145	do_wakeup = true;	153	do_wakeup = true;
146		154
147	spinlock_unlock(&wq->lock);	155	spinlock_unlock(&wq->lock);
148	t->sleep_queue = NULL;	156	t->sleep_queue = NULL;
149	}	157	}
150	spinlock_unlock(&t->lock);	158	spinlock_unlock(&t->lock);
151		159
152	if (do_wakeup)	160	if (do_wakeup)
153	thread_ready(t);	161	thread_ready(t);
154		162
155	out:	163	out:
156	spinlock_unlock(&threads_lock);	164	spinlock_unlock(&threads_lock);
157	interrupts_restore(ipl);	165	interrupts_restore(ipl);
158	}	166	}
159		167
160	/** Sleep until either wakeup, timeout or interruption occurs	168	/** Sleep until either wakeup, timeout or interruption occurs
161	*	169	*
162	* This is a sleep implementation which allows itself to be	170	* This is a sleep implementation which allows itself to time out or to be
163	* interrupted from the sleep, restoring a failover context.	171	* interrupted from the sleep, restoring a failover context.
164	*	172	*
165	* Sleepers are organised in a FIFO fashion in a structure called wait queue.	173	* Sleepers are organised in a FIFO fashion in a structure called wait queue.
166	*	174	*
167	* This function is really basic in that other functions as waitq_sleep()	175	* This function is really basic in that other functions as waitq_sleep()
168	* and all the *_timeout() functions use it.	176	* and all the *_timeout() functions use it.
169	*	177	*
170	* @param wq Pointer to wait queue.	178	* @param wq Pointer to wait queue.
171	* @param usec Timeout in microseconds.	179	* @param usec Timeout in microseconds.
172	* @param nonblocking Blocking vs. non-blocking operation mode switch.	180	* @param flags Specify mode of the sleep.
173	*	181	*
-		182	* The sleep can be interrupted only if the
-		183	* SYNCH_FLAGS_INTERRUPTIBLE bit is specified in flags.
-		184
174	* If usec is greater than zero, regardless of the value of nonblocking,	185	* If usec is greater than zero, regardless of the value of the
175	* the call will not return until either timeout or wakeup comes.	186	* SYNCH_FLAGS_NON_BLOCKING bit in flags, the call will not return until either timeout,
-		187	* interruption or wakeup comes.
176	*	188	*
177	* If usec is zero and @nonblocking is zero (false), the call	189	* If usec is zero and the SYNCH_FLAGS_NON_BLOCKING bit is not set in flags, the call
178	* will not return until wakeup comes.	190	* will not return until wakeup or interruption comes.
179	*	191	*
180	* If usec is zero and nonblocking is non-zero (true), the call will	192	* If usec is zero and the SYNCH_FLAGS_NON_BLOCKING bit is set in flags, the call will
181	* immediately return, reporting either success or failure.	193	* immediately return, reporting either success or failure.
182	*	194	*
183	* @return Returns one of: ESYNCH_WOULD_BLOCK, ESYNCH_TIMEOUT,	195	* @return Returns one of: ESYNCH_WOULD_BLOCK, ESYNCH_TIMEOUT, ESYNCH_INTERRUPTED,
184	* ESYNCH_OK_ATOMIC, ESYNCH_OK_BLOCKED.	196	* ESYNCH_OK_ATOMIC, ESYNCH_OK_BLOCKED.
185	*	197	*
186	* @li ESYNCH_WOULD_BLOCK means that the sleep failed because at the time	198	* @li ESYNCH_WOULD_BLOCK means that the sleep failed because at the time
187	* of the call there was no pending wakeup.	199	* of the call there was no pending wakeup.
188	*	200	*
189	* @li ESYNCH_TIMEOUT means that the sleep timed out.	201	* @li ESYNCH_TIMEOUT means that the sleep timed out.
190	*	202	*
191	* @li ESYNCH_INTERRUPTED means that somebody interrupted the sleeping thread.	203	* @li ESYNCH_INTERRUPTED means that somebody interrupted the sleeping thread.
192	*	204	*
193	* @li ESYNCH_OK_ATOMIC means that the sleep succeeded and that there was	205	* @li ESYNCH_OK_ATOMIC means that the sleep succeeded and that there was
194	* a pending wakeup at the time of the call. The caller was not put	206	* a pending wakeup at the time of the call. The caller was not put
195	* asleep at all.	207	* asleep at all.
196	*	208	*
197	* @li ESYNCH_OK_BLOCKED means that the sleep succeeded; the full sleep was	209	* @li ESYNCH_OK_BLOCKED means that the sleep succeeded; the full sleep was
198	* attempted.	210	* attempted.
199	*/	211	*/
200	int waitq_sleep_timeout(waitq_t *wq, __u32 usec, int nonblocking)	212	int waitq_sleep_timeout(waitq_t *wq, __u32 usec, int flags)
201	{	213	{
202	ipl_t ipl;	214	ipl_t ipl;
203	int rc;	215	int rc;
204		216
205	ipl = waitq_sleep_prepare(wq);	217	ipl = waitq_sleep_prepare(wq);
206	rc = waitq_sleep_timeout_unsafe(wq, usec, nonblocking);	218	rc = waitq_sleep_timeout_unsafe(wq, usec, flags);
207	waitq_sleep_finish(wq, rc, ipl);	219	waitq_sleep_finish(wq, rc, ipl);
208	return rc;	220	return rc;
209	}	221	}
210		222
211	/** Prepare to sleep in a waitq.	223	/** Prepare to sleep in a waitq.
212	*	224	*
213	* This function will return holding the lock of the wait queue	225	* This function will return holding the lock of the wait queue
214	* and interrupts disabled.	226	* and interrupts disabled.
215	*	227	*
216	* @param wq Wait queue.	228	* @param wq Wait queue.
217	*	229	*
218	* @return Interrupt level as it existed on entry to this function.	230	* @return Interrupt level as it existed on entry to this function.
219	*/	231	*/
220	ipl_t waitq_sleep_prepare(waitq_t *wq)	232	ipl_t waitq_sleep_prepare(waitq_t *wq)
221	{	233	{
222	ipl_t ipl;	234	ipl_t ipl;
223		235
224	restart:	236	restart:
225	ipl = interrupts_disable();	237	ipl = interrupts_disable();
226		238
227	if (THREAD) { /* needed during system initiailzation */	239	if (THREAD) { /* needed during system initiailzation */
228	/*	240	/*
229	* Busy waiting for a delayed timeout.	241	* Busy waiting for a delayed timeout.
230	* This is an important fix for the race condition between	242	* This is an important fix for the race condition between
231	* a delayed timeout and a next call to waitq_sleep_timeout().	243	* a delayed timeout and a next call to waitq_sleep_timeout().
232	* Simply, the thread is not allowed to go to sleep if	244	* Simply, the thread is not allowed to go to sleep if
233	* there are timeouts in progress.	245	* there are timeouts in progress.
234	*/	246	*/
235	spinlock_lock(&THREAD->lock);	247	spinlock_lock(&THREAD->lock);
236	if (THREAD->timeout_pending) {	248	if (THREAD->timeout_pending) {
237	spinlock_unlock(&THREAD->lock);	249	spinlock_unlock(&THREAD->lock);
238	interrupts_restore(ipl);	250	interrupts_restore(ipl);
239	goto restart;	251	goto restart;
240	}	252	}
241	spinlock_unlock(&THREAD->lock);	253	spinlock_unlock(&THREAD->lock);
242	}	254	}
243		255
244	spinlock_lock(&wq->lock);	256	spinlock_lock(&wq->lock);
245	return ipl;	257	return ipl;
246	}	258	}
247		259
248	/** Finish waiting in a wait queue.	260	/** Finish waiting in a wait queue.
249	*	261	*
250	* This function restores interrupts to the state that existed prior	262	* This function restores interrupts to the state that existed prior
251	* to the call to waitq_sleep_prepare(). If necessary, the wait queue	263	* to the call to waitq_sleep_prepare(). If necessary, the wait queue
252	* lock is released.	264	* lock is released.
253	*	265	*
254	* @param wq Wait queue.	266	* @param wq Wait queue.
255	* @param rc Return code of waitq_sleep_timeout_unsafe().	267	* @param rc Return code of waitq_sleep_timeout_unsafe().
256	* @param ipl Interrupt level returned by waitq_sleep_prepare().	268	* @param ipl Interrupt level returned by waitq_sleep_prepare().
257	*/	269	*/
258	void waitq_sleep_finish(waitq_t *wq, int rc, ipl_t ipl)	270	void waitq_sleep_finish(waitq_t *wq, int rc, ipl_t ipl)
259	{	271	{
260	switch (rc) {	272	switch (rc) {
261	case ESYNCH_WOULD_BLOCK:	273	case ESYNCH_WOULD_BLOCK:
262	case ESYNCH_OK_ATOMIC:	274	case ESYNCH_OK_ATOMIC:
263	spinlock_unlock(&wq->lock);	275	spinlock_unlock(&wq->lock);
264	break;	276	break;
265	default:	277	default:
266	break;	278	break;
267	}	279	}
268	interrupts_restore(ipl);	280	interrupts_restore(ipl);
269	}	281	}
270		282
271	/** Internal implementation of waitq_sleep_timeout().	283	/** Internal implementation of waitq_sleep_timeout().
272	*	284	*
273	* This function implements logic of sleeping in a wait queue.	285	* This function implements logic of sleeping in a wait queue.
274	* This call must be preceeded by a call to waitq_sleep_prepare()	286	* This call must be preceeded by a call to waitq_sleep_prepare()
275	* and followed by a call to waitq_slee_finish().	287	* and followed by a call to waitq_slee_finish().
276	*	288	*
277	* @param wq See waitq_sleep_timeout().	289	* @param wq See waitq_sleep_timeout().
278	* @param usec See waitq_sleep_timeout().	290	* @param usec See waitq_sleep_timeout().
279	* @param nonblocking See waitq_sleep_timeout().	291	* @param flags See waitq_sleep_timeout().
280	*	292	*
281	* @return See waitq_sleep_timeout().	293	* @return See waitq_sleep_timeout().
282	*/	294	*/
283	int waitq_sleep_timeout_unsafe(waitq_t *wq, __u32 usec, int nonblocking)	295	int waitq_sleep_timeout_unsafe(waitq_t *wq, __u32 usec, int flags)
284	{	296	{
285	/* checks whether to go to sleep at all */	297	/* checks whether to go to sleep at all */
286	if (wq->missed_wakeups) {	298	if (wq->missed_wakeups) {
287	wq->missed_wakeups--;	299	wq->missed_wakeups--;
288	return ESYNCH_OK_ATOMIC;	300	return ESYNCH_OK_ATOMIC;
289	}	301	}
290	else {	302	else {
291	if (nonblocking && (usec == 0)) {	303	if ((flags & SYNCH_FLAGS_NON_BLOCKING) && (usec == 0)) {
292	/* return immediatelly instead of going to sleep */	304	/* return immediatelly instead of going to sleep */
293	return ESYNCH_WOULD_BLOCK;	305	return ESYNCH_WOULD_BLOCK;
294	}	306	}
295	}	307	}
296		308
297	/*	309	/*
298	* Now we are firmly decided to go to sleep.	310	* Now we are firmly decided to go to sleep.
299	*/	311	*/
300	spinlock_lock(&THREAD->lock);	312	spinlock_lock(&THREAD->lock);
301		313
-		314	if (flags & SYNCH_FLAGS_INTERRUPTIBLE) {
302	/*	315	/*
303	* Set context that will be restored if the sleep	316	* Set context that will be restored if the sleep
304	* of this thread is ever interrupted.	317	* of this thread is ever interrupted.
305	*/	318	*/
-		319	THREAD->sleep_interruptible = true;
306	if (!context_save(&THREAD->sleep_interruption_context)) {	320	if (!context_save(&THREAD->sleep_interruption_context)) {
307	/* Short emulation of scheduler() return code. */	321	/* Short emulation of scheduler() return code. */
308	spinlock_unlock(&THREAD->lock);	322	spinlock_unlock(&THREAD->lock);
309	return ESYNCH_INTERRUPTED;	323	return ESYNCH_INTERRUPTED;
-		324	}
-		325	} else {
-		326	THREAD->sleep_interruptible = false;
310	}	327	}
311		328
312	if (usec) {	329	if (usec) {
313	/* We use the timeout variant. */	330	/* We use the timeout variant. */
314	if (!context_save(&THREAD->sleep_timeout_context)) {	331	if (!context_save(&THREAD->sleep_timeout_context)) {
315	/* Short emulation of scheduler() return code. */	332	/* Short emulation of scheduler() return code. */
316	spinlock_unlock(&THREAD->lock);	333	spinlock_unlock(&THREAD->lock);
317	return ESYNCH_TIMEOUT;	334	return ESYNCH_TIMEOUT;
318	}	335	}
319	THREAD->timeout_pending = true;	336	THREAD->timeout_pending = true;
320	timeout_register(&THREAD->sleep_timeout, (__u64) usec, waitq_timeouted_sleep, THREAD);	337	timeout_register(&THREAD->sleep_timeout, (__u64) usec, waitq_timeouted_sleep, THREAD);
321	}	338	}
322		339
323	list_append(&THREAD->wq_link, &wq->head);	340	list_append(&THREAD->wq_link, &wq->head);
324		341
325	/*	342	/*
326	* Suspend execution.	343	* Suspend execution.
327	*/	344	*/
328	THREAD->state = Sleeping;	345	THREAD->state = Sleeping;
329	THREAD->sleep_queue = wq;	346	THREAD->sleep_queue = wq;
330		347
331	spinlock_unlock(&THREAD->lock);	348	spinlock_unlock(&THREAD->lock);
332		349
333	scheduler(); /* wq->lock is released in scheduler_separated_stack() */	350	scheduler(); /* wq->lock is released in scheduler_separated_stack() */
334		351
335	return ESYNCH_OK_BLOCKED;	352	return ESYNCH_OK_BLOCKED;
336	}	353	}
337		354
338		355
339	/** Wake up first thread sleeping in a wait queue	356	/** Wake up first thread sleeping in a wait queue
340	*	357	*
341	* Wake up first thread sleeping in a wait queue.	358	* Wake up first thread sleeping in a wait queue.
342	* This is the SMP- and IRQ-safe wrapper meant for	359	* This is the SMP- and IRQ-safe wrapper meant for
343	* general use.	360	* general use.
344	*	361	*
345	* Besides its 'normal' wakeup operation, it attempts	362	* Besides its 'normal' wakeup operation, it attempts
346	* to unregister possible timeout.	363	* to unregister possible timeout.
347	*	364	*
348	* @param wq Pointer to wait queue.	365	* @param wq Pointer to wait queue.
349	* @param all If this is non-zero, all sleeping threads	366	* @param all If this is non-zero, all sleeping threads
350	* will be woken up and missed count will be zeroed.	367	* will be woken up and missed count will be zeroed.
351	*/	368	*/
352	void waitq_wakeup(waitq_t *wq, bool all)	369	void waitq_wakeup(waitq_t *wq, bool all)
353	{	370	{
354	ipl_t ipl;	371	ipl_t ipl;
355		372
356	ipl = interrupts_disable();	373	ipl = interrupts_disable();
357	spinlock_lock(&wq->lock);	374	spinlock_lock(&wq->lock);
358		375
359	_waitq_wakeup_unsafe(wq, all);	376	_waitq_wakeup_unsafe(wq, all);
360		377
361	spinlock_unlock(&wq->lock);	378	spinlock_unlock(&wq->lock);
362	interrupts_restore(ipl);	379	interrupts_restore(ipl);
363	}	380	}
364		381
365	/** Internal SMP- and IRQ-unsafe version of waitq_wakeup()	382	/** Internal SMP- and IRQ-unsafe version of waitq_wakeup()
366	*	383	*
367	* This is the internal SMP- and IRQ-unsafe version	384	* This is the internal SMP- and IRQ-unsafe version
368	* of waitq_wakeup(). It assumes wq->lock is already	385	* of waitq_wakeup(). It assumes wq->lock is already
369	* locked and interrupts are already disabled.	386	* locked and interrupts are already disabled.
370	*	387	*
371	* @param wq Pointer to wait queue.	388	* @param wq Pointer to wait queue.
372	* @param all If this is non-zero, all sleeping threads	389	* @param all If this is non-zero, all sleeping threads
373	* will be woken up and missed count will be zeroed.	390	* will be woken up and missed count will be zeroed.
374	*/	391	*/
375	void _waitq_wakeup_unsafe(waitq_t *wq, bool all)	392	void _waitq_wakeup_unsafe(waitq_t *wq, bool all)
376	{	393	{
377	thread_t *t;	394	thread_t *t;
378		395
379	loop:	396	loop:
380	if (list_empty(&wq->head)) {	397	if (list_empty(&wq->head)) {
381	wq->missed_wakeups++;	398	wq->missed_wakeups++;
382	if (all)	399	if (all)
383	wq->missed_wakeups = 0;	400	wq->missed_wakeups = 0;
384	return;	401	return;
385	}	402	}
386		403
387	t = list_get_instance(wq->head.next, thread_t, wq_link);	404	t = list_get_instance(wq->head.next, thread_t, wq_link);
388		405
389	list_remove(&t->wq_link);	406	list_remove(&t->wq_link);
390	spinlock_lock(&t->lock);	407	spinlock_lock(&t->lock);
391	if (t->timeout_pending && timeout_unregister(&t->sleep_timeout))	408	if (t->timeout_pending && timeout_unregister(&t->sleep_timeout))
392	t->timeout_pending = false;	409	t->timeout_pending = false;
393	t->sleep_queue = NULL;	410	t->sleep_queue = NULL;
394	spinlock_unlock(&t->lock);	411	spinlock_unlock(&t->lock);
395		412
396	thread_ready(t);	413	thread_ready(t);
397		414
398	if (all)	415	if (all)
399	goto loop;	416	goto loop;
400	}	417	}
401		418

Subversion Repositories HelenOS-historic

(root)/kernel/trunk/generic/src/synch/waitq.c – Rev 1467 → 1502