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glibc/linuxthreads/semaphore.c
Ulrich Drepper 57642a7892 Update. 
2001-09-11  Ulrich Drepper  <drepper@redhat.com>

	* nscd/nscd_gethst_r.c: Don't expect IPv6 addresses for IPv4 lookup.
	Patch by Stephan Kulow.
2001-09-12 03:53:07 +00:00

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/* Linuxthreads - a simple clone()-based implementation of Posix */
/* threads for Linux. */
/* Copyright (C) 1996 Xavier Leroy (Xavier.Leroy@inria.fr) */
/* */
/* This program is free software; you can redistribute it and/or */
/* modify it under the terms of the GNU Library General Public License */
/* as published by the Free Software Foundation; either version 2 */
/* of the License, or (at your option) any later version. */
/* */
/* This program is distributed in the hope that it will be useful, */
/* but WITHOUT ANY WARRANTY; without even the implied warranty of */
/* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the */
/* GNU Library General Public License for more details. */
/* Semaphores a la POSIX 1003.1b */
#include <errno.h>
#include "pthread.h"
#include "semaphore.h"
#include "internals.h"
#include "spinlock.h"
#include "restart.h"
#include "queue.h"
#include <shlib-compat.h>
int __new_sem_init(sem_t *sem, int pshared, unsigned int value)
{
if (value > SEM_VALUE_MAX) {
errno = EINVAL;
return -1;
}
if (pshared) {
errno = ENOSYS;
return -1;
}
__pthread_init_lock(&sem->__sem_lock);
sem->__sem_value = value;
sem->__sem_waiting = NULL;
return 0;
}
/* Function called by pthread_cancel to remove the thread from
waiting inside __new_sem_wait. */
static int new_sem_extricate_func(void *obj, pthread_descr th)
{
volatile pthread_descr self = thread_self();
sem_t *sem = obj;
int did_remove = 0;
__pthread_lock(&sem->__sem_lock, self);
did_remove = remove_from_queue(&sem->__sem_waiting, th);
__pthread_unlock(&sem->__sem_lock);
return did_remove;
}
int __new_sem_wait(sem_t * sem)
{
volatile pthread_descr self = thread_self();
pthread_extricate_if extr;
int already_canceled = 0;
int spurious_wakeup_count;
/* Set up extrication interface */
extr.pu_object = sem;
extr.pu_extricate_func = new_sem_extricate_func;
__pthread_lock(&sem->__sem_lock, self);
if (sem->__sem_value > 0) {
sem->__sem_value--;
__pthread_unlock(&sem->__sem_lock);
return 0;
}
/* Register extrication interface */
THREAD_SETMEM(self, p_sem_avail, 0);
__pthread_set_own_extricate_if(self, &extr);
/* Enqueue only if not already cancelled. */
if (!(THREAD_GETMEM(self, p_canceled)
&& THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE))
enqueue(&sem->__sem_waiting, self);
else
already_canceled = 1;
__pthread_unlock(&sem->__sem_lock);
if (already_canceled) {
__pthread_set_own_extricate_if(self, 0);
__pthread_do_exit(PTHREAD_CANCELED, CURRENT_STACK_FRAME);
}
/* Wait for sem_post or cancellation, or fall through if already canceled */
spurious_wakeup_count = 0;
while (1)
{
suspend(self);
if (THREAD_GETMEM(self, p_sem_avail) == 0
&& (THREAD_GETMEM(self, p_woken_by_cancel) == 0
|| THREAD_GETMEM(self, p_cancelstate) != PTHREAD_CANCEL_ENABLE))
{
/* Count resumes that don't belong to us. */
spurious_wakeup_count++;
continue;
}
break;
}
__pthread_set_own_extricate_if(self, 0);
/* Terminate only if the wakeup came from cancellation. */
/* Otherwise ignore cancellation because we got the semaphore. */
if (THREAD_GETMEM(self, p_woken_by_cancel)
&& THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE) {
THREAD_SETMEM(self, p_woken_by_cancel, 0);
__pthread_do_exit(PTHREAD_CANCELED, CURRENT_STACK_FRAME);
}
/* We got the semaphore */
return 0;
}
int __new_sem_trywait(sem_t * sem)
{
int retval;
__pthread_lock(&sem->__sem_lock, NULL);
if (sem->__sem_value == 0) {
errno = EAGAIN;
retval = -1;
} else {
sem->__sem_value--;
retval = 0;
}
__pthread_unlock(&sem->__sem_lock);
return retval;
}
int __new_sem_post(sem_t * sem)
{
pthread_descr self = thread_self();
pthread_descr th;
struct pthread_request request;
if (THREAD_GETMEM(self, p_in_sighandler) == NULL) {
__pthread_lock(&sem->__sem_lock, self);
if (sem->__sem_waiting == NULL) {
if (sem->__sem_value >= SEM_VALUE_MAX) {
/* Overflow */
errno = ERANGE;
__pthread_unlock(&sem->__sem_lock);
return -1;
}
sem->__sem_value++;
__pthread_unlock(&sem->__sem_lock);
} else {
th = dequeue(&sem->__sem_waiting);
__pthread_unlock(&sem->__sem_lock);
th->p_sem_avail = 1;
WRITE_MEMORY_BARRIER();
restart(th);
}
} else {
/* If we're in signal handler, delegate post operation to
the thread manager. */
if (__pthread_manager_request < 0) {
if (__pthread_initialize_manager() < 0) {
errno = EAGAIN;
return -1;
}
}
request.req_kind = REQ_POST;
request.req_args.post = sem;
TEMP_FAILURE_RETRY(__libc_write(__pthread_manager_request,
(char *) &request, sizeof(request)));
}
return 0;
}
int __new_sem_getvalue(sem_t * sem, int * sval)
{
*sval = sem->__sem_value;
return 0;
}
int __new_sem_destroy(sem_t * sem)
{
if (sem->__sem_waiting != NULL) {
__set_errno (EBUSY);
return -1;
}
return 0;
}
sem_t *sem_open(const char *name, int oflag, ...)
{
__set_errno (ENOSYS);
return SEM_FAILED;
}
int sem_close(sem_t *sem)
{
__set_errno (ENOSYS);
return -1;
}
int sem_unlink(const char *name)
{
__set_errno (ENOSYS);
return -1;
}
int sem_timedwait(sem_t *sem, const struct timespec *abstime)
{
pthread_descr self = thread_self();
pthread_extricate_if extr;
int already_canceled = 0;
int spurious_wakeup_count;
__pthread_lock(&sem->__sem_lock, self);
if (sem->__sem_value > 0) {
--sem->__sem_value;
__pthread_unlock(&sem->__sem_lock);
return 0;
}
if (abstime->tv_nsec < 0 || abstime->tv_nsec >= 1000000000) {
/* The standard requires that if the function would block and the
time value is illegal, the function returns with an error. */
__pthread_unlock(&sem->__sem_lock);
return EINVAL;
}
/* Set up extrication interface */
extr.pu_object = sem;
extr.pu_extricate_func = new_sem_extricate_func;
/* Register extrication interface */
THREAD_SETMEM(self, p_sem_avail, 0);
__pthread_set_own_extricate_if(self, &extr);
/* Enqueue only if not already cancelled. */
if (!(THREAD_GETMEM(self, p_canceled)
&& THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE))
enqueue(&sem->__sem_waiting, self);
else
already_canceled = 1;
__pthread_unlock(&sem->__sem_lock);
if (already_canceled) {
__pthread_set_own_extricate_if(self, 0);
__pthread_do_exit(PTHREAD_CANCELED, CURRENT_STACK_FRAME);
}
spurious_wakeup_count = 0;
while (1)
{
if (timedsuspend(self, abstime) == 0) {
int was_on_queue;
/* __pthread_lock will queue back any spurious restarts that
may happen to it. */
__pthread_lock(&sem->__sem_lock, self);
was_on_queue = remove_from_queue(&sem->__sem_waiting, self);
__pthread_unlock(&sem->__sem_lock);
if (was_on_queue) {
__pthread_set_own_extricate_if(self, 0);
return ETIMEDOUT;
}
/* Eat the outstanding restart() from the signaller */
suspend(self);
}
if (THREAD_GETMEM(self, p_sem_avail) == 0
&& (THREAD_GETMEM(self, p_woken_by_cancel) == 0
|| THREAD_GETMEM(self, p_cancelstate) != PTHREAD_CANCEL_ENABLE))
{
/* Count resumes that don't belong to us. */
spurious_wakeup_count++;
continue;
}
break;
}
__pthread_set_own_extricate_if(self, 0);
/* Terminate only if the wakeup came from cancellation. */
/* Otherwise ignore cancellation because we got the semaphore. */
if (THREAD_GETMEM(self, p_woken_by_cancel)
&& THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE) {
THREAD_SETMEM(self, p_woken_by_cancel, 0);
__pthread_do_exit(PTHREAD_CANCELED, CURRENT_STACK_FRAME);
}
/* We got the semaphore */
return 0;
}
versioned_symbol (libpthread, __new_sem_init, sem_init, GLIBC_2_1);
versioned_symbol (libpthread, __new_sem_wait, sem_wait, GLIBC_2_1);
versioned_symbol (libpthread, __new_sem_trywait, sem_trywait, GLIBC_2_1);
versioned_symbol (libpthread, __new_sem_post, sem_post, GLIBC_2_1);
versioned_symbol (libpthread, __new_sem_getvalue, sem_getvalue, GLIBC_2_1);
versioned_symbol (libpthread, __new_sem_destroy, sem_destroy, GLIBC_2_1);
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