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();
 
    /*
     * 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 1288	Rev 1375
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		-
161	/** Sleep until either wakeup, timeout or interruption occurs	160	/** Sleep until either wakeup, timeout or interruption occurs
162	*	161	*
163	* This is a sleep implementation which allows itself to be	162	* This is a sleep implementation which allows itself to be
164	* interrupted from the sleep, restoring a failover context.	163	* interrupted from the sleep, restoring a failover context.
165	*	164	*
166	* Sleepers are organised in FIFO fashion in a structure called wait queue.	165	* Sleepers are organised in a FIFO fashion in a structure called wait queue.
167	*	166	*
168	* 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()
169	* and all the *_timeout() functions use it.	168	* and all the *_timeout() functions use it.
170	*	169	*
171	* @param wq Pointer to wait queue.	170	* @param wq Pointer to wait queue.
172	* @param usec Timeout in microseconds.	171	* @param usec Timeout in microseconds.
173	* @param nonblocking Blocking vs. non-blocking operation mode switch.	172	* @param nonblocking Blocking vs. non-blocking operation mode switch.
174	*	173	*
175	* 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,
176	* the call will not return until either timeout or wakeup comes.	175	* the call will not return until either timeout or wakeup comes.
177	*	176	*
178	* If usec is zero and @nonblocking is zero (false), the call	177	* If usec is zero and @nonblocking is zero (false), the call
179	* will not return until wakeup comes.	178	* will not return until wakeup comes.
180	*	179	*
181	* 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
182	* immediately return, reporting either success or failure.	181	* immediately return, reporting either success or failure.
183	*	182	*
184	* @return Returns one of: ESYNCH_WOULD_BLOCK, ESYNCH_TIMEOUT,	183	* @return Returns one of: ESYNCH_WOULD_BLOCK, ESYNCH_TIMEOUT,
185	* ESYNCH_OK_ATOMIC, ESYNCH_OK_BLOCKED.	184	* ESYNCH_OK_ATOMIC, ESYNCH_OK_BLOCKED.
186	*	185	*
187	* @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
188	* of the call there was no pending wakeup.	187	* of the call there was no pending wakeup.
189	*	188	*
190	* @li ESYNCH_TIMEOUT means that the sleep timed out.	189	* @li ESYNCH_TIMEOUT means that the sleep timed out.
191	*	190	*
192	* @li ESYNCH_INTERRUPTED means that somebody interrupted the sleeping thread.	191	* @li ESYNCH_INTERRUPTED means that somebody interrupted the sleeping thread.
193	*	192	*
194	* @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
195	* 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
196	* asleep at all.	195	* asleep at all.
197	*	196	*
198	* @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
199	* attempted.	198	* attempted.
200	*/	199	*/
201	int waitq_sleep_timeout(waitq_t *wq, __u32 usec, int nonblocking)	200	int waitq_sleep_timeout(waitq_t *wq, __u32 usec, int nonblocking)
202	{	201	{
203	volatile ipl_t ipl; /* must be live after context_restore() */	202	ipl_t ipl;
-		203	int rc;
204		204
-		205	ipl = waitq_sleep_prepare(wq);
-		206	rc = waitq_sleep_timeout_unsafe(wq, usec, nonblocking);
-		207	waitq_sleep_finish(wq, rc, ipl);
-		208	return rc;
-		209	}
-		210
-		211	/** Prepare to sleep in a waitq.
-		212	*
-		213	* This function will return holding the lock of the wait queue
-		214	* and interrupts disabled.
-		215	*
-		216	* @param wq Wait queue.
-		217	*
-		218	* @return Interrupt level as it existed on entry to this function.
-		219	*/
-		220	ipl_t waitq_sleep_prepare(waitq_t *wq)
-		221	{
-		222	ipl_t ipl;
205		223
206	restart:	224	restart:
207	ipl = interrupts_disable();	225	ipl = interrupts_disable();
208		226
209	/*	227	/*
210	* Busy waiting for a delayed timeout.	228	* Busy waiting for a delayed timeout.
211	* This is an important fix for the race condition between	229	* This is an important fix for the race condition between
212	* a delayed timeout and a next call to waitq_sleep_timeout().	230	* a delayed timeout and a next call to waitq_sleep_timeout().
213	* Simply, the thread is not allowed to go to sleep if	231	* Simply, the thread is not allowed to go to sleep if
214	* there are timeouts in progress.	232	* there are timeouts in progress.
215	*/	233	*/
216	spinlock_lock(&THREAD->lock);	234	spinlock_lock(&THREAD->lock);
217	if (THREAD->timeout_pending) {	235	if (THREAD->timeout_pending) {
218	spinlock_unlock(&THREAD->lock);	236	spinlock_unlock(&THREAD->lock);
219	interrupts_restore(ipl);	237	interrupts_restore(ipl);
220	goto restart;	238	goto restart;
221	}	239	}
222	spinlock_unlock(&THREAD->lock);	240	spinlock_unlock(&THREAD->lock);
223		241
224	spinlock_lock(&wq->lock);	242	spinlock_lock(&wq->lock);
-		243	return ipl;
-		244	}
-		245
-		246	/** Finish waiting in a wait queue.
-		247	*
-		248	* This function restores interrupts to the state that existed prior
-		249	* to the call to waitq_sleep_prepare(). If necessary, the wait queue
-		250	* lock is released.
-		251	*
-		252	* @param wq Wait queue.
-		253	* @param rc Return code of waitq_sleep_timeout_unsafe().
-		254	* @param ipl Interrupt level returned by waitq_sleep_prepare().
-		255	*/
-		256	void waitq_sleep_finish(waitq_t *wq, int rc, ipl_t ipl)
-		257	{
-		258	switch (rc) {
-		259	case ESYNCH_WOULD_BLOCK:
-		260	case ESYNCH_OK_ATOMIC:
-		261	spinlock_unlock(&wq->lock);
-		262	break;
-		263	default:
-		264	break;
225		265	}
-		266	interrupts_restore(ipl);
-		267	}
-		268
-		269	/** Internal implementation of waitq_sleep_timeout().
-		270	*
-		271	* This function implements logic of sleeping in a wait queue.
-		272	* This call must be preceeded by a call to waitq_sleep_prepare()
-		273	* and followed by a call to waitq_slee_finish().
-		274	*
-		275	* @param wq See waitq_sleep_timeout().
-		276	* @param usec See waitq_sleep_timeout().
-		277	* @param nonblocking See waitq_sleep_timeout().
-		278	*
-		279	* @return See waitq_sleep_timeout().
-		280	*/
-		281	int waitq_sleep_timeout_unsafe(waitq_t *wq, __u32 usec, int nonblocking)
-		282	{
226	/* checks whether to go to sleep at all */	283	/* checks whether to go to sleep at all */
227	if (wq->missed_wakeups) {	284	if (wq->missed_wakeups) {
228	wq->missed_wakeups--;	285	wq->missed_wakeups--;
229	spinlock_unlock(&wq->lock);	-
230	interrupts_restore(ipl);	-
231	return ESYNCH_OK_ATOMIC;	286	return ESYNCH_OK_ATOMIC;
232	}	287	}
233	else {	288	else {
234	if (nonblocking && (usec == 0)) {	289	if (nonblocking && (usec == 0)) {
235	/* return immediatelly instead of going to sleep */	290	/* return immediatelly instead of going to sleep */
236	spinlock_unlock(&wq->lock);	-
237	interrupts_restore(ipl);	-
238	return ESYNCH_WOULD_BLOCK;	291	return ESYNCH_WOULD_BLOCK;
239	}	292	}
240	}	293	}
241		294
242	/*	295	/*
243	* Now we are firmly decided to go to sleep.	296	* Now we are firmly decided to go to sleep.
244	*/	297	*/
245	spinlock_lock(&THREAD->lock);	298	spinlock_lock(&THREAD->lock);
246		299
247	/*	300	/*
248	* Set context that will be restored if the sleep	301	* Set context that will be restored if the sleep
249	* of this thread is ever interrupted.	302	* of this thread is ever interrupted.
250	*/	303	*/
251	if (!context_save(&THREAD->sleep_interruption_context)) {	304	if (!context_save(&THREAD->sleep_interruption_context)) {
252	/* Short emulation of scheduler() return code. */	305	/* Short emulation of scheduler() return code. */
253	spinlock_unlock(&THREAD->lock);	306	spinlock_unlock(&THREAD->lock);
254	interrupts_restore(ipl);	-
255	return ESYNCH_INTERRUPTED;	307	return ESYNCH_INTERRUPTED;
256	}	308	}
257		309
258	if (usec) {	310	if (usec) {
259	/* We use the timeout variant. */	311	/* We use the timeout variant. */
260	if (!context_save(&THREAD->sleep_timeout_context)) {	312	if (!context_save(&THREAD->sleep_timeout_context)) {
261	/* Short emulation of scheduler() return code. */	313	/* Short emulation of scheduler() return code. */
262	spinlock_unlock(&THREAD->lock);	314	spinlock_unlock(&THREAD->lock);
263	interrupts_restore(ipl);	-
264	return ESYNCH_TIMEOUT;	315	return ESYNCH_TIMEOUT;
265	}	316	}
266	THREAD->timeout_pending = true;	317	THREAD->timeout_pending = true;
267	timeout_register(&THREAD->sleep_timeout, (__u64) usec, waitq_timeouted_sleep, THREAD);	318	timeout_register(&THREAD->sleep_timeout, (__u64) usec, waitq_timeouted_sleep, THREAD);
268	}	319	}
269		320
270	list_append(&THREAD->wq_link, &wq->head);	321	list_append(&THREAD->wq_link, &wq->head);
271		322
272	/*	323	/*
273	* Suspend execution.	324	* Suspend execution.
274	*/	325	*/
275	THREAD->state = Sleeping;	326	THREAD->state = Sleeping;
276	THREAD->sleep_queue = wq;	327	THREAD->sleep_queue = wq;
277		328
278	spinlock_unlock(&THREAD->lock);	329	spinlock_unlock(&THREAD->lock);
279		330
280	scheduler(); /* wq->lock is released in scheduler_separated_stack() */	331	scheduler(); /* wq->lock is released in scheduler_separated_stack() */
281	interrupts_restore(ipl);	-
282		332
283	return ESYNCH_OK_BLOCKED;	333	return ESYNCH_OK_BLOCKED;
284	}	334	}
285		335
286		336
287	/** Wake up first thread sleeping in a wait queue	337	/** Wake up first thread sleeping in a wait queue
288	*	338	*
289	* Wake up first thread sleeping in a wait queue.	339	* Wake up first thread sleeping in a wait queue.
290	* This is the SMP- and IRQ-safe wrapper meant for	340	* This is the SMP- and IRQ-safe wrapper meant for
291	* general use.	341	* general use.
292	*	342	*
293	* Besides its 'normal' wakeup operation, it attempts	343	* Besides its 'normal' wakeup operation, it attempts
294	* to unregister possible timeout.	344	* to unregister possible timeout.
295	*	345	*
296	* @param wq Pointer to wait queue.	346	* @param wq Pointer to wait queue.
297	* @param all If this is non-zero, all sleeping threads	347	* @param all If this is non-zero, all sleeping threads
298	* will be woken up and missed count will be zeroed.	348	* will be woken up and missed count will be zeroed.
299	*/	349	*/
300	void waitq_wakeup(waitq_t *wq, bool all)	350	void waitq_wakeup(waitq_t *wq, bool all)
301	{	351	{
302	ipl_t ipl;	352	ipl_t ipl;
303		353
304	ipl = interrupts_disable();	354	ipl = interrupts_disable();
305	spinlock_lock(&wq->lock);	355	spinlock_lock(&wq->lock);
306		356
307	_waitq_wakeup_unsafe(wq, all);	357	_waitq_wakeup_unsafe(wq, all);
308		358
309	spinlock_unlock(&wq->lock);	359	spinlock_unlock(&wq->lock);
310	interrupts_restore(ipl);	360	interrupts_restore(ipl);
311	}	361	}
312		362
313	/** Internal SMP- and IRQ-unsafe version of waitq_wakeup()	363	/** Internal SMP- and IRQ-unsafe version of waitq_wakeup()
314	*	364	*
315	* This is the internal SMP- and IRQ-unsafe version	365	* This is the internal SMP- and IRQ-unsafe version
316	* of waitq_wakeup(). It assumes wq->lock is already	366	* of waitq_wakeup(). It assumes wq->lock is already
317	* locked and interrupts are already disabled.	367	* locked and interrupts are already disabled.
318	*	368	*
319	* @param wq Pointer to wait queue.	369	* @param wq Pointer to wait queue.
320	* @param all If this is non-zero, all sleeping threads	370	* @param all If this is non-zero, all sleeping threads
321	* will be woken up and missed count will be zeroed.	371	* will be woken up and missed count will be zeroed.
322	*/	372	*/
323	void _waitq_wakeup_unsafe(waitq_t *wq, bool all)	373	void _waitq_wakeup_unsafe(waitq_t *wq, bool all)
324	{	374	{
325	thread_t *t;	375	thread_t *t;
326		376
327	loop:	377	loop:
328	if (list_empty(&wq->head)) {	378	if (list_empty(&wq->head)) {
329	wq->missed_wakeups++;	379	wq->missed_wakeups++;
330	if (all)	380	if (all)
331	wq->missed_wakeups = 0;	381	wq->missed_wakeups = 0;
332	return;	382	return;
333	}	383	}
334		384
335	t = list_get_instance(wq->head.next, thread_t, wq_link);	385	t = list_get_instance(wq->head.next, thread_t, wq_link);
336		386
337	list_remove(&t->wq_link);	387	list_remove(&t->wq_link);
338	spinlock_lock(&t->lock);	388	spinlock_lock(&t->lock);
339	if (t->timeout_pending && timeout_unregister(&t->sleep_timeout))	389	if (t->timeout_pending && timeout_unregister(&t->sleep_timeout))
340	t->timeout_pending = false;	390	t->timeout_pending = false;
341	t->sleep_queue = NULL;	391	t->sleep_queue = NULL;
342	spinlock_unlock(&t->lock);	392	spinlock_unlock(&t->lock);
343		393
344	thread_ready(t);	394	thread_ready(t);
345		395
346	if (all)	396	if (all)
347	goto loop;	397	goto loop;
348	}	398	}
349		399

Subversion Repositories HelenOS-historic

(root)/kernel/trunk/generic/src/synch/waitq.c – Rev 1288 → 1375