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Finish user stack support. Change locking code to be safe in situations with different priorities.

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1998-06-25 19:27  Ulrich Drepper  <drepper@cygnus.com>

	* attr.c: Finish user stack support.  Change locking code to be safe
	in situations with different priorities.
	* cancel.c: Likewise.
	* condvar.c: Likewise.
	* internals.h: Likewise.
	* join.c: Likewise.
	* manager.c: Likewise.
	* mutex.c: Likewise.
	* pthread.c: Likewise.
	* ptlongjmp.c: Likewise.
	* queue.h: Likewise.
	* rwlock.c: Likewise.
	* semaphore.c: Likewise.
	* semaphore.h: Likewise.
	* signals.c: Likewise.
	* spinlock.c: Likewise.
	* spinlock.h: Likewise.
	Patches by Xavier leroy.

1998-06-25  Ulrich Drepper  <drepper@cygnus.com>

	* sysdeps/pthread/pthread.h: Make [sg]et_stacksize and
	[sg]et_stackaddr prototypes always available.

	* sysdeps/unix/sysv/linux/bits/posix_opt.h: Define
	_POSIX_THREAD_ATTR_STACKSIZE and _POSIX_THREAD_ATTR_STACKADDR.
This commit is contained in:
Ulrich Drepper
1998-06-25 19:36:00 +00:00
parent d47aac3999
commit 3387a425e6
23 changed files with 633 additions and 512 deletions
Download Patch File Download Diff File Expand all files Collapse all files

232
linuxthreads/semaphore.c
View File

@@ -17,69 +17,13 @@
#include "pthread.h"
#include "semaphore.h"
#include "internals.h"
#include "spinlock.h"
#include "restart.h"
#if !defined HAS_COMPARE_AND_SWAP && !defined TEST_FOR_COMPARE_AND_SWAP
/* If we have no atomic compare and swap, fake it using an extra spinlock. */
#include "spinlock.h"
static inline int sem_compare_and_swap(sem_t *sem, long oldval, long newval)
{
int ret;
acquire(&sem->sem_spinlock);
ret = (sem->sem_status == oldval);
if (ret) sem->sem_status = newval;
release(&sem->sem_spinlock);
return ret;
}
#elif defined TEST_FOR_COMPARE_AND_SWAP
#include "spinlock.h"
static int has_compare_and_swap = -1; /* to be determined at run-time */
static inline int sem_compare_and_swap(sem_t *sem, long oldval, long newval)
{
int ret;
if (has_compare_and_swap == 1)
return __compare_and_swap(&sem->sem_status, oldval, newval);
acquire(&sem->sem_spinlock);
ret = (sem->sem_status == oldval);
if (ret) sem->sem_status = newval;
release(&sem->sem_spinlock);
return ret;
}
#else
/* But if we do have an atomic compare and swap, use it! */
static inline int sem_compare_and_swap(sem_t *sem, long oldval, long newval)
{
return __compare_and_swap(&sem->sem_status, oldval, newval);
}
#endif
/* The state of a semaphore is represented by a long int encoding
either the semaphore count if >= 0 and no thread is waiting on it,
or the head of the list of threads waiting for the semaphore.
To distinguish the two cases, we encode the semaphore count N
as 2N+1, so that it has the lowest bit set.
A sequence of sem_wait operations on a semaphore initialized to N
result in the following successive states:
2N+1, 2N-1, ..., 3, 1, &first_waiting_thread, &second_waiting_thread, ...
*/
static void sem_restart_list(pthread_descr waiting);
#include "queue.h"
int sem_init(sem_t *sem, int pshared, unsigned int value)
{
if ((long)value > SEM_VALUE_MAX) {
if (value > SEM_VALUE_MAX) {
errno = EINVAL;
return -1;
}
@@ -87,150 +31,104 @@ int sem_init(sem_t *sem, int pshared, unsigned int value)
errno = ENOSYS;
return -1;
}
#ifdef TEST_FOR_COMPARE_AND_SWAP
if (has_compare_and_swap == -1) {
has_compare_and_swap = compare_and_swap_is_available();
}
#endif
#if !defined HAS_COMPARE_AND_SWAP || defined TEST_FOR_COMPARE_AND_SWAP
sem->sem_spinlock = 0;
#endif
sem->sem_status = ((long)value << 1) + 1;
__pthread_init_lock((struct _pthread_fastlock *) &sem->sem_lock);
sem->sem_value = value;
sem->sem_waiting = NULL;
return 0;
}
int sem_wait(sem_t * sem)
{
long oldstatus, newstatus;
volatile pthread_descr self = thread_self();
pthread_descr * th;
volatile pthread_descr self;
while (1) {
do {
oldstatus = sem->sem_status;
if ((oldstatus & 1) && (oldstatus != 1))
newstatus = oldstatus - 2;
else {
newstatus = (long) self;
self->p_nextwaiting = (pthread_descr) oldstatus;
}
}
while (! sem_compare_and_swap(sem, oldstatus, newstatus));
if (newstatus & 1)
/* We got the semaphore. */
return 0;
/* Wait for sem_post or cancellation */
suspend_with_cancellation(self);
/* This is a cancellation point */
if (self->p_canceled && self->p_cancelstate == PTHREAD_CANCEL_ENABLE) {
/* Remove ourselves from the waiting list if we're still on it */
/* First check if we're at the head of the list. */
do {
oldstatus = sem->sem_status;
if (oldstatus != (long) self) break;
newstatus = (long) self->p_nextwaiting;
}
while (! sem_compare_and_swap(sem, oldstatus, newstatus));
/* Now, check if we're somewhere in the list.
There's a race condition with sem_post here, but it does not matter:
the net result is that at the time pthread_exit is called,
self is no longer reachable from sem->sem_status. */
if (oldstatus != (long) self && (oldstatus & 1) == 0) {
for (th = &(((pthread_descr) oldstatus)->p_nextwaiting);
*th != NULL && *th != (pthread_descr) 1;
th = &((*th)->p_nextwaiting)) {
if (*th == self) {
*th = self->p_nextwaiting;
break;
}
}
}
pthread_exit(PTHREAD_CANCELED);
}
__pthread_lock((struct _pthread_fastlock *) &sem->sem_lock);
if (sem->sem_value > 0) {
sem->sem_value--;
__pthread_unlock((struct _pthread_fastlock *) &sem->sem_lock);
return 0;
}
self = thread_self();
enqueue(&sem->sem_waiting, self);
/* Wait for sem_post or cancellation */
__pthread_unlock((struct _pthread_fastlock *) &sem->sem_lock);
suspend_with_cancellation(self);
/* This is a cancellation point */
if (self->p_canceled && self->p_cancelstate == PTHREAD_CANCEL_ENABLE) {
/* Remove ourselves from the waiting list if we're still on it */
__pthread_lock((struct _pthread_fastlock *) &sem->sem_lock);
remove_from_queue(&sem->sem_waiting, self);
__pthread_unlock((struct _pthread_fastlock *) &sem->sem_lock);
pthread_exit(PTHREAD_CANCELED);
}
/* We got the semaphore */
return 0;
}
int sem_trywait(sem_t * sem)
{
long oldstatus, newstatus;
int retval;
do {
oldstatus = sem->sem_status;
if ((oldstatus & 1) == 0 || (oldstatus == 1)) {
errno = EAGAIN;
return -1;
}
newstatus = oldstatus - 2;
__pthread_lock((struct _pthread_fastlock *) &sem->sem_lock);
if (sem->sem_value == 0) {
errno = EAGAIN;
retval = -1;
} else {
sem->sem_value--;
retval = 0;
}
while (! sem_compare_and_swap(sem, oldstatus, newstatus));
return 0;
return retval;
}
int sem_post(sem_t * sem)
{
long oldstatus, newstatus;
pthread_descr self = thread_self();
pthread_descr th;
struct pthread_request request;
do {
oldstatus = sem->sem_status;
if ((oldstatus & 1) == 0)
newstatus = 3;
else {
if (oldstatus >= SEM_VALUE_MAX) {
if (self->p_in_sighandler == NULL) {
__pthread_lock((struct _pthread_fastlock *) &sem->sem_lock);
if (sem->sem_waiting == NULL) {
if (sem->sem_value >= SEM_VALUE_MAX) {
/* Overflow */
errno = ERANGE;
__pthread_unlock((struct _pthread_fastlock *) &sem->sem_lock);
return -1;
}
newstatus = oldstatus + 2;
sem->sem_value++;
__pthread_unlock((struct _pthread_fastlock *) &sem->sem_lock);
} else {
th = dequeue(&sem->sem_waiting);
__pthread_unlock((struct _pthread_fastlock *) &sem->sem_lock);
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;
__libc_write(__pthread_manager_request,
(char *) &request, sizeof(request));
}
while (! sem_compare_and_swap(sem, oldstatus, newstatus));
if ((oldstatus & 1) == 0)
sem_restart_list((pthread_descr) oldstatus);
return 0;
}
int sem_getvalue(sem_t * sem, int * sval)
{
long status = sem->sem_status;
if (status & 1)
*sval = (int)((unsigned long) status >> 1);
else
*sval = 0;
*sval = sem->sem_value;
return 0;
}
int sem_destroy(sem_t * sem)
{
if ((sem->sem_status & 1) == 0) {
if (sem->sem_waiting != NULL) {
errno = EBUSY;
return -1;
}
return 0;
}
/* Auxiliary function for restarting all threads on a waiting list,
in priority order. */
static void sem_restart_list(pthread_descr waiting)
{
pthread_descr th, towake, *p;
/* Sort list of waiting threads by decreasing priority (insertion sort) */
towake = NULL;
while (waiting != (pthread_descr) 1) {
th = waiting;
waiting = waiting->p_nextwaiting;
p = &towake;
while (*p != NULL && th->p_priority < (*p)->p_priority)
p = &((*p)->p_nextwaiting);
th->p_nextwaiting = *p;
*p = th;
}
/* Wake up threads in priority order */
while (towake != NULL) {
th = towake;
towake = towake->p_nextwaiting;
th->p_nextwaiting = NULL;
restart(th);
}
}