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 (!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 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 nonblocking Blocking vs. non-blocking operation mode switch.
 *
 * If usec is greater than zero, regardless of the value of nonblocking,
 * the call will not return until either timeout or wakeup comes.
 *
 * If usec is zero and @nonblocking is zero (false), the call
 * will not return until wakeup comes.
 *
 * If usec is zero and nonblocking is non-zero (true), the call will
 * immediately return, reporting either success or failure.
 *
 * @return  Returns one of: ESYNCH_WOULD_BLOCK, ESYNCH_TIMEOUT,
 *          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 nonblocking)
{
    ipl_t ipl;
    int rc;
   
    ipl = waitq_sleep_prepare(wq);
    rc = waitq_sleep_timeout_unsafe(wq, usec, nonblocking);
    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 nonblocking See waitq_sleep_timeout().
 *
 * @return See waitq_sleep_timeout().
 */
int waitq_sleep_timeout_unsafe(waitq_t *wq, __u32 usec, int nonblocking)
{
    /* checks whether to go to sleep at all */
    if (wq->missed_wakeups) {
        wq->missed_wakeups--;
        return ESYNCH_OK_ATOMIC;
    }
    else {
        if (nonblocking && (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);
 
    /*
     * Set context that will be restored if the sleep
     * of this thread is ever interrupted.
     */
    if (!context_save(&THREAD->sleep_interruption_context)) {
        /* Short emulation of scheduler() return code. */
        spinlock_unlock(&THREAD->lock);
        return ESYNCH_INTERRUPTED;
    }
 
    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 1375	Rev 1467
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 (!spinlock_trylock(&wq->lock)) {	138	if (!spinlock_trylock(&wq->lock)) {
139	spinlock_unlock(&t->lock);	139	spinlock_unlock(&t->lock);
140	goto grab_locks; /* avoid deadlock */	140	goto grab_locks; /* avoid deadlock */
141	}	141	}
142		142
143	list_remove(&t->wq_link);	143	list_remove(&t->wq_link);
144	t->saved_context = t->sleep_interruption_context;	144	t->saved_context = t->sleep_interruption_context;
145	do_wakeup = true;	145	do_wakeup = true;
146		146
147	spinlock_unlock(&wq->lock);	147	spinlock_unlock(&wq->lock);
148	t->sleep_queue = NULL;	148	t->sleep_queue = NULL;
149	}	149	}
150	spinlock_unlock(&t->lock);	150	spinlock_unlock(&t->lock);
151		151
152	if (do_wakeup)	152	if (do_wakeup)
153	thread_ready(t);	153	thread_ready(t);
154		154
155	out:	155	out:
156	spinlock_unlock(&threads_lock);	156	spinlock_unlock(&threads_lock);
157	interrupts_restore(ipl);	157	interrupts_restore(ipl);
158	}	158	}
159		159
160	/** Sleep until either wakeup, timeout or interruption occurs	160	/** Sleep until either wakeup, timeout or interruption occurs
161	*	161	*
162	* This is a sleep implementation which allows itself to be	162	* This is a sleep implementation which allows itself to be
163	* interrupted from the sleep, restoring a failover context.	163	* interrupted from the sleep, restoring a failover context.
164	*	164	*
165	* Sleepers are organised in a FIFO fashion in a structure called wait queue.	165	* Sleepers are organised in a FIFO fashion in a structure called wait queue.
166	*	166	*
167	* This function is really basic in that other functions as waitq_sleep()	167	* This function is really basic in that other functions as waitq_sleep()
168	* and all the *_timeout() functions use it.	168	* and all the *_timeout() functions use it.
169	*	169	*
170	* @param wq Pointer to wait queue.	170	* @param wq Pointer to wait queue.
171	* @param usec Timeout in microseconds.	171	* @param usec Timeout in microseconds.
172	* @param nonblocking Blocking vs. non-blocking operation mode switch.	172	* @param nonblocking Blocking vs. non-blocking operation mode switch.
173	*	173	*
174	* If usec is greater than zero, regardless of the value of nonblocking,	174	* If usec is greater than zero, regardless of the value of nonblocking,
175	* the call will not return until either timeout or wakeup comes.	175	* the call will not return until either timeout or wakeup comes.
176	*	176	*
177	* If usec is zero and @nonblocking is zero (false), the call	177	* If usec is zero and @nonblocking is zero (false), the call
178	* will not return until wakeup comes.	178	* will not return until wakeup comes.
179	*	179	*
180	* If usec is zero and nonblocking is non-zero (true), the call will	180	* If usec is zero and nonblocking is non-zero (true), the call will
181	* immediately return, reporting either success or failure.	181	* immediately return, reporting either success or failure.
182	*	182	*
183	* @return Returns one of: ESYNCH_WOULD_BLOCK, ESYNCH_TIMEOUT,	183	* @return Returns one of: ESYNCH_WOULD_BLOCK, ESYNCH_TIMEOUT,
184	* ESYNCH_OK_ATOMIC, ESYNCH_OK_BLOCKED.	184	* ESYNCH_OK_ATOMIC, ESYNCH_OK_BLOCKED.
185	*	185	*
186	* @li ESYNCH_WOULD_BLOCK means that the sleep failed because at the time	186	* @li ESYNCH_WOULD_BLOCK means that the sleep failed because at the time
187	* of the call there was no pending wakeup.	187	* of the call there was no pending wakeup.
188	*	188	*
189	* @li ESYNCH_TIMEOUT means that the sleep timed out.	189	* @li ESYNCH_TIMEOUT means that the sleep timed out.
190	*	190	*
191	* @li ESYNCH_INTERRUPTED means that somebody interrupted the sleeping thread.	191	* @li ESYNCH_INTERRUPTED means that somebody interrupted the sleeping thread.
192	*	192	*
193	* @li ESYNCH_OK_ATOMIC means that the sleep succeeded and that there was	193	* @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	194	* a pending wakeup at the time of the call. The caller was not put
195	* asleep at all.	195	* asleep at all.
196	*	196	*
197	* @li ESYNCH_OK_BLOCKED means that the sleep succeeded; the full sleep was	197	* @li ESYNCH_OK_BLOCKED means that the sleep succeeded; the full sleep was
198	* attempted.	198	* attempted.
199	*/	199	*/
200	int waitq_sleep_timeout(waitq_t *wq, __u32 usec, int nonblocking)	200	int waitq_sleep_timeout(waitq_t *wq, __u32 usec, int nonblocking)
201	{	201	{
202	ipl_t ipl;	202	ipl_t ipl;
203	int rc;	203	int rc;
204		204
205	ipl = waitq_sleep_prepare(wq);	205	ipl = waitq_sleep_prepare(wq);
206	rc = waitq_sleep_timeout_unsafe(wq, usec, nonblocking);	206	rc = waitq_sleep_timeout_unsafe(wq, usec, nonblocking);
207	waitq_sleep_finish(wq, rc, ipl);	207	waitq_sleep_finish(wq, rc, ipl);
208	return rc;	208	return rc;
209	}	209	}
210		210
211	/** Prepare to sleep in a waitq.	211	/** Prepare to sleep in a waitq.
212	*	212	*
213	* This function will return holding the lock of the wait queue	213	* This function will return holding the lock of the wait queue
214	* and interrupts disabled.	214	* and interrupts disabled.
215	*	215	*
216	* @param wq Wait queue.	216	* @param wq Wait queue.
217	*	217	*
218	* @return Interrupt level as it existed on entry to this function.	218	* @return Interrupt level as it existed on entry to this function.
219	*/	219	*/
220	ipl_t waitq_sleep_prepare(waitq_t *wq)	220	ipl_t waitq_sleep_prepare(waitq_t *wq)
221	{	221	{
222	ipl_t ipl;	222	ipl_t ipl;
223		223
224	restart:	224	restart:
225	ipl = interrupts_disable();	225	ipl = interrupts_disable();
226		226
-		227	if (THREAD) { /* needed during system initiailzation */
227	/*	228	/*
228	* Busy waiting for a delayed timeout.	229	* Busy waiting for a delayed timeout.
229	* This is an important fix for the race condition between	230	* This is an important fix for the race condition between
230	* a delayed timeout and a next call to waitq_sleep_timeout().	231	* a delayed timeout and a next call to waitq_sleep_timeout().
231	* Simply, the thread is not allowed to go to sleep if	232	* Simply, the thread is not allowed to go to sleep if
232	* there are timeouts in progress.	233	* there are timeouts in progress.
233	*/	234	*/
234	spinlock_lock(&THREAD->lock);	235	spinlock_lock(&THREAD->lock);
235	if (THREAD->timeout_pending) {	236	if (THREAD->timeout_pending) {
-		237	spinlock_unlock(&THREAD->lock);
-		238	interrupts_restore(ipl);
-		239	goto restart;
-		240	}
236	spinlock_unlock(&THREAD->lock);	241	spinlock_unlock(&THREAD->lock);
237	interrupts_restore(ipl);	-
238	goto restart;	-
239	}	242	}
240	spinlock_unlock(&THREAD->lock);	-
241		243
242	spinlock_lock(&wq->lock);	244	spinlock_lock(&wq->lock);
243	return ipl;	245	return ipl;
244	}	246	}
245		247
246	/** Finish waiting in a wait queue.	248	/** Finish waiting in a wait queue.
247	*	249	*
248	* This function restores interrupts to the state that existed prior	250	* This function restores interrupts to the state that existed prior
249	* to the call to waitq_sleep_prepare(). If necessary, the wait queue	251	* to the call to waitq_sleep_prepare(). If necessary, the wait queue
250	* lock is released.	252	* lock is released.
251	*	253	*
252	* @param wq Wait queue.	254	* @param wq Wait queue.
253	* @param rc Return code of waitq_sleep_timeout_unsafe().	255	* @param rc Return code of waitq_sleep_timeout_unsafe().
254	* @param ipl Interrupt level returned by waitq_sleep_prepare().	256	* @param ipl Interrupt level returned by waitq_sleep_prepare().
255	*/	257	*/
256	void waitq_sleep_finish(waitq_t *wq, int rc, ipl_t ipl)	258	void waitq_sleep_finish(waitq_t *wq, int rc, ipl_t ipl)
257	{	259	{
258	switch (rc) {	260	switch (rc) {
259	case ESYNCH_WOULD_BLOCK:	261	case ESYNCH_WOULD_BLOCK:
260	case ESYNCH_OK_ATOMIC:	262	case ESYNCH_OK_ATOMIC:
261	spinlock_unlock(&wq->lock);	263	spinlock_unlock(&wq->lock);
262	break;	264	break;
263	default:	265	default:
264	break;	266	break;
265	}	267	}
266	interrupts_restore(ipl);	268	interrupts_restore(ipl);
267	}	269	}
268		270
269	/** Internal implementation of waitq_sleep_timeout().	271	/** Internal implementation of waitq_sleep_timeout().
270	*	272	*
271	* This function implements logic of sleeping in a wait queue.	273	* This function implements logic of sleeping in a wait queue.
272	* This call must be preceeded by a call to waitq_sleep_prepare()	274	* This call must be preceeded by a call to waitq_sleep_prepare()
273	* and followed by a call to waitq_slee_finish().	275	* and followed by a call to waitq_slee_finish().
274	*	276	*
275	* @param wq See waitq_sleep_timeout().	277	* @param wq See waitq_sleep_timeout().
276	* @param usec See waitq_sleep_timeout().	278	* @param usec See waitq_sleep_timeout().
277	* @param nonblocking See waitq_sleep_timeout().	279	* @param nonblocking See waitq_sleep_timeout().
278	*	280	*
279	* @return See waitq_sleep_timeout().	281	* @return See waitq_sleep_timeout().
280	*/	282	*/
281	int waitq_sleep_timeout_unsafe(waitq_t *wq, __u32 usec, int nonblocking)	283	int waitq_sleep_timeout_unsafe(waitq_t *wq, __u32 usec, int nonblocking)
282	{	284	{
283	/* checks whether to go to sleep at all */	285	/* checks whether to go to sleep at all */
284	if (wq->missed_wakeups) {	286	if (wq->missed_wakeups) {
285	wq->missed_wakeups--;	287	wq->missed_wakeups--;
286	return ESYNCH_OK_ATOMIC;	288	return ESYNCH_OK_ATOMIC;
287	}	289	}
288	else {	290	else {
289	if (nonblocking && (usec == 0)) {	291	if (nonblocking && (usec == 0)) {
290	/* return immediatelly instead of going to sleep */	292	/* return immediatelly instead of going to sleep */
291	return ESYNCH_WOULD_BLOCK;	293	return ESYNCH_WOULD_BLOCK;
292	}	294	}
293	}	295	}
294		296
295	/*	297	/*
296	* Now we are firmly decided to go to sleep.	298	* Now we are firmly decided to go to sleep.
297	*/	299	*/
298	spinlock_lock(&THREAD->lock);	300	spinlock_lock(&THREAD->lock);
299		301
300	/*	302	/*
301	* Set context that will be restored if the sleep	303	* Set context that will be restored if the sleep
302	* of this thread is ever interrupted.	304	* of this thread is ever interrupted.
303	*/	305	*/
304	if (!context_save(&THREAD->sleep_interruption_context)) {	306	if (!context_save(&THREAD->sleep_interruption_context)) {
305	/* Short emulation of scheduler() return code. */	307	/* Short emulation of scheduler() return code. */
306	spinlock_unlock(&THREAD->lock);	308	spinlock_unlock(&THREAD->lock);
307	return ESYNCH_INTERRUPTED;	309	return ESYNCH_INTERRUPTED;
308	}	310	}
309		311
310	if (usec) {	312	if (usec) {
311	/* We use the timeout variant. */	313	/* We use the timeout variant. */
312	if (!context_save(&THREAD->sleep_timeout_context)) {	314	if (!context_save(&THREAD->sleep_timeout_context)) {
313	/* Short emulation of scheduler() return code. */	315	/* Short emulation of scheduler() return code. */
314	spinlock_unlock(&THREAD->lock);	316	spinlock_unlock(&THREAD->lock);
315	return ESYNCH_TIMEOUT;	317	return ESYNCH_TIMEOUT;
316	}	318	}
317	THREAD->timeout_pending = true;	319	THREAD->timeout_pending = true;
318	timeout_register(&THREAD->sleep_timeout, (__u64) usec, waitq_timeouted_sleep, THREAD);	320	timeout_register(&THREAD->sleep_timeout, (__u64) usec, waitq_timeouted_sleep, THREAD);
319	}	321	}
320		322
321	list_append(&THREAD->wq_link, &wq->head);	323	list_append(&THREAD->wq_link, &wq->head);
322		324
323	/*	325	/*
324	* Suspend execution.	326	* Suspend execution.
325	*/	327	*/
326	THREAD->state = Sleeping;	328	THREAD->state = Sleeping;
327	THREAD->sleep_queue = wq;	329	THREAD->sleep_queue = wq;
328		330
329	spinlock_unlock(&THREAD->lock);	331	spinlock_unlock(&THREAD->lock);
330		332
331	scheduler(); /* wq->lock is released in scheduler_separated_stack() */	333	scheduler(); /* wq->lock is released in scheduler_separated_stack() */
332		334
333	return ESYNCH_OK_BLOCKED;	335	return ESYNCH_OK_BLOCKED;
334	}	336	}
335		337
336		338
337	/** Wake up first thread sleeping in a wait queue	339	/** Wake up first thread sleeping in a wait queue
338	*	340	*
339	* Wake up first thread sleeping in a wait queue.	341	* Wake up first thread sleeping in a wait queue.
340	* This is the SMP- and IRQ-safe wrapper meant for	342	* This is the SMP- and IRQ-safe wrapper meant for
341	* general use.	343	* general use.
342	*	344	*
343	* Besides its 'normal' wakeup operation, it attempts	345	* Besides its 'normal' wakeup operation, it attempts
344	* to unregister possible timeout.	346	* to unregister possible timeout.
345	*	347	*
346	* @param wq Pointer to wait queue.	348	* @param wq Pointer to wait queue.
347	* @param all If this is non-zero, all sleeping threads	349	* @param all If this is non-zero, all sleeping threads
348	* will be woken up and missed count will be zeroed.	350	* will be woken up and missed count will be zeroed.
349	*/	351	*/
350	void waitq_wakeup(waitq_t *wq, bool all)	352	void waitq_wakeup(waitq_t *wq, bool all)
351	{	353	{
352	ipl_t ipl;	354	ipl_t ipl;
353		355
354	ipl = interrupts_disable();	356	ipl = interrupts_disable();
355	spinlock_lock(&wq->lock);	357	spinlock_lock(&wq->lock);
356		358
357	_waitq_wakeup_unsafe(wq, all);	359	_waitq_wakeup_unsafe(wq, all);
358		360
359	spinlock_unlock(&wq->lock);	361	spinlock_unlock(&wq->lock);
360	interrupts_restore(ipl);	362	interrupts_restore(ipl);
361	}	363	}
362		364
363	/** Internal SMP- and IRQ-unsafe version of waitq_wakeup()	365	/** Internal SMP- and IRQ-unsafe version of waitq_wakeup()
364	*	366	*
365	* This is the internal SMP- and IRQ-unsafe version	367	* This is the internal SMP- and IRQ-unsafe version
366	* of waitq_wakeup(). It assumes wq->lock is already	368	* of waitq_wakeup(). It assumes wq->lock is already
367	* locked and interrupts are already disabled.	369	* locked and interrupts are already disabled.
368	*	370	*
369	* @param wq Pointer to wait queue.	371	* @param wq Pointer to wait queue.
370	* @param all If this is non-zero, all sleeping threads	372	* @param all If this is non-zero, all sleeping threads
371	* will be woken up and missed count will be zeroed.	373	* will be woken up and missed count will be zeroed.
372	*/	374	*/
373	void _waitq_wakeup_unsafe(waitq_t *wq, bool all)	375	void _waitq_wakeup_unsafe(waitq_t *wq, bool all)
374	{	376	{
375	thread_t *t;	377	thread_t *t;
376		378
377	loop:	379	loop:
378	if (list_empty(&wq->head)) {	380	if (list_empty(&wq->head)) {
379	wq->missed_wakeups++;	381	wq->missed_wakeups++;
380	if (all)	382	if (all)
381	wq->missed_wakeups = 0;	383	wq->missed_wakeups = 0;
382	return;	384	return;
383	}	385	}
384		386
385	t = list_get_instance(wq->head.next, thread_t, wq_link);	387	t = list_get_instance(wq->head.next, thread_t, wq_link);
386		388
387	list_remove(&t->wq_link);	389	list_remove(&t->wq_link);
388	spinlock_lock(&t->lock);	390	spinlock_lock(&t->lock);
389	if (t->timeout_pending && timeout_unregister(&t->sleep_timeout))	391	if (t->timeout_pending && timeout_unregister(&t->sleep_timeout))
390	t->timeout_pending = false;	392	t->timeout_pending = false;
391	t->sleep_queue = NULL;	393	t->sleep_queue = NULL;
392	spinlock_unlock(&t->lock);	394	spinlock_unlock(&t->lock);
393		395
394	thread_ready(t);	396	thread_ready(t);
395		397
396	if (all)	398	if (all)
397	goto loop;	399	goto loop;
398	}	400	}
399		401

Subversion Repositories HelenOS-historic

(root)/kernel/trunk/generic/src/synch/waitq.c – Rev 1375 → 1467