diff options
Diffstat (limited to 'pthread_cond_signal.c')
-rw-r--r-- | pthread_cond_signal.c | 125 |
1 files changed, 1 insertions, 124 deletions
diff --git a/pthread_cond_signal.c b/pthread_cond_signal.c index 220a5dd..2b4f6d4 100644 --- a/pthread_cond_signal.c +++ b/pthread_cond_signal.c @@ -36,130 +36,7 @@ * * ------------------------------------------------------------- * 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; - * } - * ------------------------------------------------------------- - * + * See the comments at the top of pthread_cond_wait.c. */ #include "pthread.h" |