summaryrefslogtreecommitdiff
path: root/pthreads/src/pthread_cond_wait.c
diff options
context:
space:
mode:
Diffstat (limited to 'pthreads/src/pthread_cond_wait.c')
-rw-r--r--pthreads/src/pthread_cond_wait.c567
1 files changed, 567 insertions, 0 deletions
diff --git a/pthreads/src/pthread_cond_wait.c b/pthreads/src/pthread_cond_wait.c
new file mode 100644
index 0000000..359219a
--- /dev/null
+++ b/pthreads/src/pthread_cond_wait.c
@@ -0,0 +1,567 @@
+/*
+ * pthread_cond_wait.c
+ *
+ * Description:
+ * This translation unit implements condition variables and their primitives.
+ *
+ *
+ * --------------------------------------------------------------------------
+ *
+ * Pthreads-win32 - POSIX Threads Library for Win32
+ * Copyright(C) 1998 John E. Bossom
+ * Copyright(C) 1999,2005 Pthreads-win32 contributors
+ *
+ * Contact Email: rpj@callisto.canberra.edu.au
+ *
+ * The current list of contributors is contained
+ * in the file CONTRIBUTORS included with the source
+ * code distribution. The list can also be seen at the
+ * following World Wide Web location:
+ * http://sources.redhat.com/pthreads-win32/contributors.html
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library in the file COPYING.LIB;
+ * if not, write to the Free Software Foundation, Inc.,
+ * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
+ *
+ * -------------------------------------------------------------
+ * Algorithm:
+ * The algorithm used in this implementation is that developed by
+ * Alexander Terekhov in colaboration with Louis Thomas. The bulk
+ * of the discussion is recorded in the file README.CV, which contains
+ * several generations of both colaborators original algorithms. The final
+ * algorithm used here is the one referred to as
+ *
+ * Algorithm 8a / IMPL_SEM,UNBLOCK_STRATEGY == UNBLOCK_ALL
+ *
+ * presented below in pseudo-code as it appeared:
+ *
+ *
+ * given:
+ * semBlockLock - bin.semaphore
+ * semBlockQueue - semaphore
+ * mtxExternal - mutex or CS
+ * mtxUnblockLock - mutex or CS
+ * nWaitersGone - int
+ * nWaitersBlocked - int
+ * nWaitersToUnblock - int
+ *
+ * wait( timeout ) {
+ *
+ * [auto: register int result ] // error checking omitted
+ * [auto: register int nSignalsWasLeft ]
+ * [auto: register int nWaitersWasGone ]
+ *
+ * sem_wait( semBlockLock );
+ * nWaitersBlocked++;
+ * sem_post( semBlockLock );
+ *
+ * unlock( mtxExternal );
+ * bTimedOut = sem_wait( semBlockQueue,timeout );
+ *
+ * lock( mtxUnblockLock );
+ * if ( 0 != (nSignalsWasLeft = nWaitersToUnblock) ) {
+ * if ( bTimeout ) { // timeout (or canceled)
+ * if ( 0 != nWaitersBlocked ) {
+ * nWaitersBlocked--;
+ * }
+ * else {
+ * nWaitersGone++; // count spurious wakeups.
+ * }
+ * }
+ * if ( 0 == --nWaitersToUnblock ) {
+ * if ( 0 != nWaitersBlocked ) {
+ * sem_post( semBlockLock ); // open the gate.
+ * nSignalsWasLeft = 0; // do not open the gate
+ * // below again.
+ * }
+ * else if ( 0 != (nWaitersWasGone = nWaitersGone) ) {
+ * nWaitersGone = 0;
+ * }
+ * }
+ * }
+ * else if ( INT_MAX/2 == ++nWaitersGone ) { // timeout/canceled or
+ * // spurious semaphore :-)
+ * sem_wait( semBlockLock );
+ * nWaitersBlocked -= nWaitersGone; // something is going on here
+ * // - test of timeouts? :-)
+ * sem_post( semBlockLock );
+ * nWaitersGone = 0;
+ * }
+ * unlock( mtxUnblockLock );
+ *
+ * if ( 1 == nSignalsWasLeft ) {
+ * if ( 0 != nWaitersWasGone ) {
+ * // sem_adjust( semBlockQueue,-nWaitersWasGone );
+ * while ( nWaitersWasGone-- ) {
+ * sem_wait( semBlockQueue ); // better now than spurious later
+ * }
+ * } sem_post( semBlockLock ); // open the gate
+ * }
+ *
+ * lock( mtxExternal );
+ *
+ * return ( bTimedOut ) ? ETIMEOUT : 0;
+ * }
+ *
+ * signal(bAll) {
+ *
+ * [auto: register int result ]
+ * [auto: register int nSignalsToIssue]
+ *
+ * lock( mtxUnblockLock );
+ *
+ * if ( 0 != nWaitersToUnblock ) { // the gate is closed!!!
+ * if ( 0 == nWaitersBlocked ) { // NO-OP
+ * return unlock( mtxUnblockLock );
+ * }
+ * if (bAll) {
+ * nWaitersToUnblock += nSignalsToIssue=nWaitersBlocked;
+ * nWaitersBlocked = 0;
+ * }
+ * else {
+ * nSignalsToIssue = 1;
+ * nWaitersToUnblock++;
+ * nWaitersBlocked--;
+ * }
+ * }
+ * else if ( nWaitersBlocked > nWaitersGone ) { // HARMLESS RACE CONDITION!
+ * sem_wait( semBlockLock ); // close the gate
+ * if ( 0 != nWaitersGone ) {
+ * nWaitersBlocked -= nWaitersGone;
+ * nWaitersGone = 0;
+ * }
+ * if (bAll) {
+ * nSignalsToIssue = nWaitersToUnblock = nWaitersBlocked;
+ * nWaitersBlocked = 0;
+ * }
+ * else {
+ * nSignalsToIssue = nWaitersToUnblock = 1;
+ * nWaitersBlocked--;
+ * }
+ * }
+ * else { // NO-OP
+ * return unlock( mtxUnblockLock );
+ * }
+ *
+ * unlock( mtxUnblockLock );
+ * sem_post( semBlockQueue,nSignalsToIssue );
+ * return result;
+ * }
+ * -------------------------------------------------------------
+ *
+ * Algorithm 9 / IMPL_SEM,UNBLOCK_STRATEGY == UNBLOCK_ALL
+ *
+ * presented below in pseudo-code; basically 8a...
+ * ...BUT W/O "spurious wakes" prevention:
+ *
+ *
+ * given:
+ * semBlockLock - bin.semaphore
+ * semBlockQueue - semaphore
+ * mtxExternal - mutex or CS
+ * mtxUnblockLock - mutex or CS
+ * nWaitersGone - int
+ * nWaitersBlocked - int
+ * nWaitersToUnblock - int
+ *
+ * wait( timeout ) {
+ *
+ * [auto: register int result ] // error checking omitted
+ * [auto: register int nSignalsWasLeft ]
+ *
+ * sem_wait( semBlockLock );
+ * ++nWaitersBlocked;
+ * sem_post( semBlockLock );
+ *
+ * unlock( mtxExternal );
+ * bTimedOut = sem_wait( semBlockQueue,timeout );
+ *
+ * lock( mtxUnblockLock );
+ * if ( 0 != (nSignalsWasLeft = nWaitersToUnblock) ) {
+ * --nWaitersToUnblock;
+ * }
+ * else if ( INT_MAX/2 == ++nWaitersGone ) { // timeout/canceled or
+ * // spurious semaphore :-)
+ * sem_wait( semBlockLock );
+ * nWaitersBlocked -= nWaitersGone; // something is going on here
+ * // - test of timeouts? :-)
+ * sem_post( semBlockLock );
+ * nWaitersGone = 0;
+ * }
+ * unlock( mtxUnblockLock );
+ *
+ * if ( 1 == nSignalsWasLeft ) {
+ * sem_post( semBlockLock ); // open the gate
+ * }
+ *
+ * lock( mtxExternal );
+ *
+ * return ( bTimedOut ) ? ETIMEOUT : 0;
+ * }
+ *
+ * signal(bAll) {
+ *
+ * [auto: register int result ]
+ * [auto: register int nSignalsToIssue]
+ *
+ * lock( mtxUnblockLock );
+ *
+ * if ( 0 != nWaitersToUnblock ) { // the gate is closed!!!
+ * if ( 0 == nWaitersBlocked ) { // NO-OP
+ * return unlock( mtxUnblockLock );
+ * }
+ * if (bAll) {
+ * nWaitersToUnblock += nSignalsToIssue=nWaitersBlocked;
+ * nWaitersBlocked = 0;
+ * }
+ * else {
+ * nSignalsToIssue = 1;
+ * ++nWaitersToUnblock;
+ * --nWaitersBlocked;
+ * }
+ * }
+ * else if ( nWaitersBlocked > nWaitersGone ) { // HARMLESS RACE CONDITION!
+ * sem_wait( semBlockLock ); // close the gate
+ * if ( 0 != nWaitersGone ) {
+ * nWaitersBlocked -= nWaitersGone;
+ * nWaitersGone = 0;
+ * }
+ * if (bAll) {
+ * nSignalsToIssue = nWaitersToUnblock = nWaitersBlocked;
+ * nWaitersBlocked = 0;
+ * }
+ * else {
+ * nSignalsToIssue = nWaitersToUnblock = 1;
+ * --nWaitersBlocked;
+ * }
+ * }
+ * else { // NO-OP
+ * return unlock( mtxUnblockLock );
+ * }
+ *
+ * unlock( mtxUnblockLock );
+ * sem_post( semBlockQueue,nSignalsToIssue );
+ * return result;
+ * }
+ * -------------------------------------------------------------
+ *
+ */
+
+#include "pthread.h"
+#include "implement.h"
+
+/*
+ * Arguments for cond_wait_cleanup, since we can only pass a
+ * single void * to it.
+ */
+typedef struct
+{
+ pthread_mutex_t *mutexPtr;
+ pthread_cond_t cv;
+ int *resultPtr;
+} ptw32_cond_wait_cleanup_args_t;
+
+static void PTW32_CDECL
+ptw32_cond_wait_cleanup (void *args)
+{
+ ptw32_cond_wait_cleanup_args_t *cleanup_args =
+ (ptw32_cond_wait_cleanup_args_t *) args;
+ pthread_cond_t cv = cleanup_args->cv;
+ int *resultPtr = cleanup_args->resultPtr;
+ int nSignalsWasLeft;
+ int result;
+
+ /*
+ * Whether we got here as a result of signal/broadcast or because of
+ * timeout on wait or thread cancellation we indicate that we are no
+ * longer waiting. The waiter is responsible for adjusting waiters
+ * (to)unblock(ed) counts (protected by unblock lock).
+ */
+ if ((result = pthread_mutex_lock (&(cv->mtxUnblockLock))) != 0)
+ {
+ *resultPtr = result;
+ return;
+ }
+
+ if (0 != (nSignalsWasLeft = cv->nWaitersToUnblock))
+ {
+ --(cv->nWaitersToUnblock);
+ }
+ else if (INT_MAX / 2 == ++(cv->nWaitersGone))
+ {
+ /* Use the non-cancellable version of sem_wait() */
+ if (ptw32_semwait (&(cv->semBlockLock)) != 0)
+ {
+ *resultPtr = errno;
+ /*
+ * This is a fatal error for this CV,
+ * so we deliberately don't unlock
+ * cv->mtxUnblockLock before returning.
+ */
+ return;
+ }
+ cv->nWaitersBlocked -= cv->nWaitersGone;
+ if (sem_post (&(cv->semBlockLock)) != 0)
+ {
+ *resultPtr = errno;
+ /*
+ * This is a fatal error for this CV,
+ * so we deliberately don't unlock
+ * cv->mtxUnblockLock before returning.
+ */
+ return;
+ }
+ cv->nWaitersGone = 0;
+ }
+
+ if ((result = pthread_mutex_unlock (&(cv->mtxUnblockLock))) != 0)
+ {
+ *resultPtr = result;
+ return;
+ }
+
+ if (1 == nSignalsWasLeft)
+ {
+ if (sem_post (&(cv->semBlockLock)) != 0)
+ {
+ *resultPtr = errno;
+ return;
+ }
+ }
+
+ /*
+ * XSH: Upon successful return, the mutex has been locked and is owned
+ * by the calling thread.
+ */
+ if ((result = pthread_mutex_lock (cleanup_args->mutexPtr)) != 0)
+ {
+ *resultPtr = result;
+ }
+} /* ptw32_cond_wait_cleanup */
+
+static INLINE int
+ptw32_cond_timedwait (pthread_cond_t * cond,
+ pthread_mutex_t * mutex, const struct timespec *abstime)
+{
+ int result = 0;
+ pthread_cond_t cv;
+ ptw32_cond_wait_cleanup_args_t cleanup_args;
+
+ if (cond == NULL || *cond == NULL)
+ {
+ return EINVAL;
+ }
+
+ /*
+ * We do a quick check to see if we need to do more work
+ * to initialise a static condition variable. We check
+ * again inside the guarded section of ptw32_cond_check_need_init()
+ * to avoid race conditions.
+ */
+ if (*cond == PTHREAD_COND_INITIALIZER)
+ {
+ result = ptw32_cond_check_need_init (cond);
+ }
+
+ if (result != 0 && result != EBUSY)
+ {
+ return result;
+ }
+
+ cv = *cond;
+
+ /* Thread can be cancelled in sem_wait() but this is OK */
+ if (sem_wait (&(cv->semBlockLock)) != 0)
+ {
+ return errno;
+ }
+
+ ++(cv->nWaitersBlocked);
+
+ if (sem_post (&(cv->semBlockLock)) != 0)
+ {
+ return errno;
+ }
+
+ /*
+ * Setup this waiter cleanup handler
+ */
+ cleanup_args.mutexPtr = mutex;
+ cleanup_args.cv = cv;
+ cleanup_args.resultPtr = &result;
+
+#if defined(_MSC_VER) && _MSC_VER < 1400
+#pragma inline_depth(0)
+#endif
+ pthread_cleanup_push (ptw32_cond_wait_cleanup, (void *) &cleanup_args);
+
+ /*
+ * Now we can release 'mutex' and...
+ */
+ if ((result = pthread_mutex_unlock (mutex)) == 0)
+ {
+
+ /*
+ * ...wait to be awakened by
+ * pthread_cond_signal, or
+ * pthread_cond_broadcast, or
+ * timeout, or
+ * thread cancellation
+ *
+ * Note:
+ *
+ * sem_timedwait is a cancellation point,
+ * hence providing the mechanism for making
+ * pthread_cond_wait a cancellation point.
+ * We use the cleanup mechanism to ensure we
+ * re-lock the mutex and adjust (to)unblock(ed) waiters
+ * counts if we are cancelled, timed out or signalled.
+ */
+ if (sem_timedwait (&(cv->semBlockQueue), abstime) != 0)
+ {
+ result = errno;
+ }
+ }
+
+ /*
+ * Always cleanup
+ */
+ pthread_cleanup_pop (1);
+#if defined(_MSC_VER) && _MSC_VER < 1400
+#pragma inline_depth()
+#endif
+
+ /*
+ * "result" can be modified by the cleanup handler.
+ */
+ return result;
+
+} /* ptw32_cond_timedwait */
+
+
+int
+pthread_cond_wait (pthread_cond_t * cond, pthread_mutex_t * mutex)
+ /*
+ * ------------------------------------------------------
+ * DOCPUBLIC
+ * This function waits on a condition variable until
+ * awakened by a signal or broadcast.
+ *
+ * Caller MUST be holding the mutex lock; the
+ * lock is released and the caller is blocked waiting
+ * on 'cond'. When 'cond' is signaled, the mutex
+ * is re-acquired before returning to the caller.
+ *
+ * PARAMETERS
+ * cond
+ * pointer to an instance of pthread_cond_t
+ *
+ * mutex
+ * pointer to an instance of pthread_mutex_t
+ *
+ *
+ * DESCRIPTION
+ * This function waits on a condition variable until
+ * awakened by a signal or broadcast.
+ *
+ * NOTES:
+ *
+ * 1) The function must be called with 'mutex' LOCKED
+ * by the calling thread, or undefined behaviour
+ * will result.
+ *
+ * 2) This routine atomically releases 'mutex' and causes
+ * the calling thread to block on the condition variable.
+ * The blocked thread may be awakened by
+ * pthread_cond_signal or
+ * pthread_cond_broadcast.
+ *
+ * Upon successful completion, the 'mutex' has been locked and
+ * is owned by the calling thread.
+ *
+ *
+ * RESULTS
+ * 0 caught condition; mutex released,
+ * EINVAL 'cond' or 'mutex' is invalid,
+ * EINVAL different mutexes for concurrent waits,
+ * EINVAL mutex is not held by the calling thread,
+ *
+ * ------------------------------------------------------
+ */
+{
+ /*
+ * The NULL abstime arg means INFINITE waiting.
+ */
+ return (ptw32_cond_timedwait (cond, mutex, NULL));
+
+} /* pthread_cond_wait */
+
+
+int
+pthread_cond_timedwait (pthread_cond_t * cond,
+ pthread_mutex_t * mutex,
+ const struct timespec *abstime)
+ /*
+ * ------------------------------------------------------
+ * DOCPUBLIC
+ * This function waits on a condition variable either until
+ * awakened by a signal or broadcast; or until the time
+ * specified by abstime passes.
+ *
+ * PARAMETERS
+ * cond
+ * pointer to an instance of pthread_cond_t
+ *
+ * mutex
+ * pointer to an instance of pthread_mutex_t
+ *
+ * abstime
+ * pointer to an instance of (const struct timespec)
+ *
+ *
+ * DESCRIPTION
+ * This function waits on a condition variable either until
+ * awakened by a signal or broadcast; or until the time
+ * specified by abstime passes.
+ *
+ * NOTES:
+ * 1) The function must be called with 'mutex' LOCKED
+ * by the calling thread, or undefined behaviour
+ * will result.
+ *
+ * 2) This routine atomically releases 'mutex' and causes
+ * the calling thread to block on the condition variable.
+ * The blocked thread may be awakened by
+ * pthread_cond_signal or
+ * pthread_cond_broadcast.
+ *
+ *
+ * RESULTS
+ * 0 caught condition; mutex released,
+ * EINVAL 'cond', 'mutex', or abstime is invalid,
+ * EINVAL different mutexes for concurrent waits,
+ * EINVAL mutex is not held by the calling thread,
+ * ETIMEDOUT abstime ellapsed before cond was signaled.
+ *
+ * ------------------------------------------------------
+ */
+{
+ if (abstime == NULL)
+ {
+ return EINVAL;
+ }
+
+ return (ptw32_cond_timedwait (cond, mutex, abstime));
+
+} /* pthread_cond_timedwait */
generated by cgit v1.2.3 (git 2.39.1) at 2024-04-23 14:10:49 +0000