glibc/linuxthreads/mutex.c

363 lines
11 KiB
C

/* 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. */
/* Mutexes */
#include <bits/libc-lock.h>
#include <errno.h>
#include <sched.h>
#include <stddef.h>
#include <limits.h>
#include "pthread.h"
#include "internals.h"
#include "spinlock.h"
#include "queue.h"
#include "restart.h"
int __pthread_mutex_init(pthread_mutex_t * mutex,
const pthread_mutexattr_t * mutex_attr)
{
__pthread_init_lock(&mutex->__m_lock);
mutex->__m_kind =
mutex_attr == NULL ? PTHREAD_MUTEX_TIMED_NP : mutex_attr->__mutexkind;
mutex->__m_count = 0;
mutex->__m_owner = NULL;
return 0;
}
strong_alias (__pthread_mutex_init, pthread_mutex_init)
hidden_def (__pthread_mutex_init)
int __pthread_mutex_destroy(pthread_mutex_t * mutex)
{
switch (mutex->__m_kind) {
case PTHREAD_MUTEX_ADAPTIVE_NP:
case PTHREAD_MUTEX_RECURSIVE_NP:
if ((mutex->__m_lock.__status & 1) != 0)
return EBUSY;
return 0;
case PTHREAD_MUTEX_ERRORCHECK_NP:
case PTHREAD_MUTEX_TIMED_NP:
if (mutex->__m_lock.__status != 0)
return EBUSY;
return 0;
default:
return EINVAL;
}
}
strong_alias (__pthread_mutex_destroy, pthread_mutex_destroy)
hidden_def (__pthread_mutex_destroy)
int __pthread_mutex_trylock(pthread_mutex_t * mutex)
{
pthread_descr self;
int retcode;
switch(mutex->__m_kind) {
case PTHREAD_MUTEX_ADAPTIVE_NP:
retcode = __pthread_trylock(&mutex->__m_lock);
return retcode;
case PTHREAD_MUTEX_RECURSIVE_NP:
self = thread_self();
if (mutex->__m_owner == self) {
mutex->__m_count++;
return 0;
}
retcode = __pthread_trylock(&mutex->__m_lock);
if (retcode == 0) {
mutex->__m_owner = self;
mutex->__m_count = 0;
}
return retcode;
case PTHREAD_MUTEX_ERRORCHECK_NP:
retcode = __pthread_alt_trylock(&mutex->__m_lock);
if (retcode == 0) {
mutex->__m_owner = thread_self();
}
return retcode;
case PTHREAD_MUTEX_TIMED_NP:
retcode = __pthread_alt_trylock(&mutex->__m_lock);
return retcode;
default:
return EINVAL;
}
}
strong_alias (__pthread_mutex_trylock, pthread_mutex_trylock)
hidden_def (__pthread_mutex_trylock)
int __pthread_mutex_lock(pthread_mutex_t * mutex)
{
pthread_descr self;
switch(mutex->__m_kind) {
case PTHREAD_MUTEX_ADAPTIVE_NP:
__pthread_lock(&mutex->__m_lock, NULL);
return 0;
case PTHREAD_MUTEX_RECURSIVE_NP:
self = thread_self();
if (mutex->__m_owner == self) {
mutex->__m_count++;
return 0;
}
__pthread_lock(&mutex->__m_lock, self);
mutex->__m_owner = self;
mutex->__m_count = 0;
return 0;
case PTHREAD_MUTEX_ERRORCHECK_NP:
self = thread_self();
if (mutex->__m_owner == self) return EDEADLK;
__pthread_alt_lock(&mutex->__m_lock, self);
mutex->__m_owner = self;
return 0;
case PTHREAD_MUTEX_TIMED_NP:
__pthread_alt_lock(&mutex->__m_lock, NULL);
return 0;
default:
return EINVAL;
}
}
strong_alias (__pthread_mutex_lock, pthread_mutex_lock)
hidden_def (__pthread_mutex_lock)
int __pthread_mutex_timedlock (pthread_mutex_t *mutex,
const struct timespec *abstime)
{
pthread_descr self;
int res;
if (__builtin_expect (abstime->tv_nsec, 0) < 0
|| __builtin_expect (abstime->tv_nsec, 0) >= 1000000000)
return EINVAL;
switch(mutex->__m_kind) {
case PTHREAD_MUTEX_ADAPTIVE_NP:
__pthread_lock(&mutex->__m_lock, NULL);
return 0;
case PTHREAD_MUTEX_RECURSIVE_NP:
self = thread_self();
if (mutex->__m_owner == self) {
mutex->__m_count++;
return 0;
}
__pthread_lock(&mutex->__m_lock, self);
mutex->__m_owner = self;
mutex->__m_count = 0;
return 0;
case PTHREAD_MUTEX_ERRORCHECK_NP:
self = thread_self();
if (mutex->__m_owner == self) return EDEADLK;
res = __pthread_alt_timedlock(&mutex->__m_lock, self, abstime);
if (res != 0)
{
mutex->__m_owner = self;
return 0;
}
return ETIMEDOUT;
case PTHREAD_MUTEX_TIMED_NP:
/* Only this type supports timed out lock. */
return (__pthread_alt_timedlock(&mutex->__m_lock, NULL, abstime)
? 0 : ETIMEDOUT);
default:
return EINVAL;
}
}
strong_alias (__pthread_mutex_timedlock, pthread_mutex_timedlock)
int __pthread_mutex_unlock(pthread_mutex_t * mutex)
{
switch (mutex->__m_kind) {
case PTHREAD_MUTEX_ADAPTIVE_NP:
__pthread_unlock(&mutex->__m_lock);
return 0;
case PTHREAD_MUTEX_RECURSIVE_NP:
if (mutex->__m_owner != thread_self())
return EPERM;
if (mutex->__m_count > 0) {
mutex->__m_count--;
return 0;
}
mutex->__m_owner = NULL;
__pthread_unlock(&mutex->__m_lock);
return 0;
case PTHREAD_MUTEX_ERRORCHECK_NP:
if (mutex->__m_owner != thread_self() || mutex->__m_lock.__status == 0)
return EPERM;
mutex->__m_owner = NULL;
__pthread_alt_unlock(&mutex->__m_lock);
return 0;
case PTHREAD_MUTEX_TIMED_NP:
__pthread_alt_unlock(&mutex->__m_lock);
return 0;
default:
return EINVAL;
}
}
strong_alias (__pthread_mutex_unlock, pthread_mutex_unlock)
hidden_def (__pthread_mutex_unlock)
int __pthread_mutexattr_init(pthread_mutexattr_t *attr)
{
attr->__mutexkind = PTHREAD_MUTEX_TIMED_NP;
return 0;
}
strong_alias (__pthread_mutexattr_init, pthread_mutexattr_init)
int __pthread_mutexattr_destroy(pthread_mutexattr_t *attr)
{
return 0;
}
strong_alias (__pthread_mutexattr_destroy, pthread_mutexattr_destroy)
int __pthread_mutexattr_settype(pthread_mutexattr_t *attr, int kind)
{
if (kind != PTHREAD_MUTEX_ADAPTIVE_NP
&& kind != PTHREAD_MUTEX_RECURSIVE_NP
&& kind != PTHREAD_MUTEX_ERRORCHECK_NP
&& kind != PTHREAD_MUTEX_TIMED_NP)
return EINVAL;
attr->__mutexkind = kind;
return 0;
}
weak_alias (__pthread_mutexattr_settype, pthread_mutexattr_settype)
strong_alias ( __pthread_mutexattr_settype, __pthread_mutexattr_setkind_np)
weak_alias (__pthread_mutexattr_setkind_np, pthread_mutexattr_setkind_np)
int __pthread_mutexattr_gettype(const pthread_mutexattr_t *attr, int *kind)
{
*kind = attr->__mutexkind;
return 0;
}
weak_alias (__pthread_mutexattr_gettype, pthread_mutexattr_gettype)
strong_alias (__pthread_mutexattr_gettype, __pthread_mutexattr_getkind_np)
weak_alias (__pthread_mutexattr_getkind_np, pthread_mutexattr_getkind_np)
int __pthread_mutexattr_getpshared (const pthread_mutexattr_t *attr,
int *pshared)
{
*pshared = PTHREAD_PROCESS_PRIVATE;
return 0;
}
weak_alias (__pthread_mutexattr_getpshared, pthread_mutexattr_getpshared)
int __pthread_mutexattr_setpshared (pthread_mutexattr_t *attr, int pshared)
{
if (pshared != PTHREAD_PROCESS_PRIVATE && pshared != PTHREAD_PROCESS_SHARED)
return EINVAL;
/* For now it is not possible to shared a conditional variable. */
if (pshared != PTHREAD_PROCESS_PRIVATE)
return ENOSYS;
return 0;
}
weak_alias (__pthread_mutexattr_setpshared, pthread_mutexattr_setpshared)
/* Once-only execution */
static pthread_mutex_t once_masterlock = PTHREAD_MUTEX_INITIALIZER;
static pthread_cond_t once_finished = PTHREAD_COND_INITIALIZER;
static int fork_generation = 0; /* Child process increments this after fork. */
enum { NEVER = 0, IN_PROGRESS = 1, DONE = 2 };
/* If a thread is canceled while calling the init_routine out of
pthread once, this handler will reset the once_control variable
to the NEVER state. */
static void pthread_once_cancelhandler(void *arg)
{
pthread_once_t *once_control = arg;
pthread_mutex_lock(&once_masterlock);
*once_control = NEVER;
pthread_mutex_unlock(&once_masterlock);
pthread_cond_broadcast(&once_finished);
}
int __pthread_once(pthread_once_t * once_control, void (*init_routine)(void))
{
/* flag for doing the condition broadcast outside of mutex */
int state_changed;
/* Test without locking first for speed */
if (*once_control == DONE) {
READ_MEMORY_BARRIER();
return 0;
}
/* Lock and test again */
state_changed = 0;
pthread_mutex_lock(&once_masterlock);
/* If this object was left in an IN_PROGRESS state in a parent
process (indicated by stale generation field), reset it to NEVER. */
if ((*once_control & 3) == IN_PROGRESS && (*once_control & ~3) != fork_generation)
*once_control = NEVER;
/* If init_routine is being called from another routine, wait until
it completes. */
while ((*once_control & 3) == IN_PROGRESS) {
pthread_cond_wait(&once_finished, &once_masterlock);
}
/* Here *once_control is stable and either NEVER or DONE. */
if (*once_control == NEVER) {
*once_control = IN_PROGRESS | fork_generation;
pthread_mutex_unlock(&once_masterlock);
pthread_cleanup_push(pthread_once_cancelhandler, once_control);
init_routine();
pthread_cleanup_pop(0);
pthread_mutex_lock(&once_masterlock);
WRITE_MEMORY_BARRIER();
*once_control = DONE;
state_changed = 1;
}
pthread_mutex_unlock(&once_masterlock);
if (state_changed)
pthread_cond_broadcast(&once_finished);
return 0;
}
strong_alias (__pthread_once, pthread_once)
/*
* Handle the state of the pthread_once mechanism across forks. The
* once_masterlock is acquired in the parent process prior to a fork to ensure
* that no thread is in the critical region protected by the lock. After the
* fork, the lock is released. In the child, the lock and the condition
* variable are simply reset. The child also increments its generation
* counter which lets pthread_once calls detect stale IN_PROGRESS states
* and reset them back to NEVER.
*/
void __pthread_once_fork_prepare(void)
{
pthread_mutex_lock(&once_masterlock);
}
void __pthread_once_fork_parent(void)
{
pthread_mutex_unlock(&once_masterlock);
}
void __pthread_once_fork_child(void)
{
pthread_mutex_init(&once_masterlock, NULL);
pthread_cond_init(&once_finished, NULL);
if (fork_generation <= INT_MAX - 4)
fork_generation += 4; /* leave least significant two bits zero */
else
fork_generation = 0;
}