diff options
Diffstat (limited to 'nsprpub/pr/src/bthreads/btcvar.c')
| -rw-r--r-- | nsprpub/pr/src/bthreads/btcvar.c | 244 |
1 files changed, 244 insertions, 0 deletions
diff --git a/nsprpub/pr/src/bthreads/btcvar.c b/nsprpub/pr/src/bthreads/btcvar.c new file mode 100644 index 000000000..c74837907 --- /dev/null +++ b/nsprpub/pr/src/bthreads/btcvar.c @@ -0,0 +1,244 @@ +/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */ +/* This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ + +#include <kernel/OS.h> + +#include "primpl.h" + +/* +** Create a new condition variable. +** +** "lock" is the lock used to protect the condition variable. +** +** Condition variables are synchronization objects that threads can use +** to wait for some condition to occur. +** +** This may fail if memory is tight or if some operating system resource +** is low. In such cases, a NULL will be returned. +*/ +PR_IMPLEMENT(PRCondVar*) + PR_NewCondVar (PRLock *lock) +{ + PRCondVar *cv = PR_NEW( PRCondVar ); + PR_ASSERT( NULL != lock ); + if( NULL != cv ) + { + cv->lock = lock; + cv->sem = create_sem(0, "CVSem"); + cv->handshakeSem = create_sem(0, "CVHandshake"); + cv->signalSem = create_sem( 0, "CVSignal"); + cv->signalBenCount = 0; + cv->ns = cv->nw = 0; + PR_ASSERT( cv->sem >= B_NO_ERROR ); + PR_ASSERT( cv->handshakeSem >= B_NO_ERROR ); + PR_ASSERT( cv->signalSem >= B_NO_ERROR ); + } + return cv; +} /* PR_NewCondVar */ + +/* +** Destroy a condition variable. There must be no thread +** waiting on the condvar. The caller is responsible for guaranteeing +** that the condvar is no longer in use. +** +*/ +PR_IMPLEMENT(void) + PR_DestroyCondVar (PRCondVar *cvar) +{ + status_t result = delete_sem( cvar->sem ); + PR_ASSERT( result == B_NO_ERROR ); + + result = delete_sem( cvar->handshakeSem ); + PR_ASSERT( result == B_NO_ERROR ); + + result = delete_sem( cvar->signalSem ); + PR_ASSERT( result == B_NO_ERROR ); + + PR_DELETE( cvar ); +} + +/* +** The thread that waits on a condition is blocked in a "waiting on +** condition" state until another thread notifies the condition or a +** caller specified amount of time expires. The lock associated with +** the condition variable will be released, which must have be held +** prior to the call to wait. +** +** Logically a notified thread is moved from the "waiting on condition" +** state and made "ready." When scheduled, it will attempt to reacquire +** the lock that it held when wait was called. +** +** The timeout has two well known values, PR_INTERVAL_NO_TIMEOUT and +** PR_INTERVAL_NO_WAIT. The former value requires that a condition be +** notified (or the thread interrupted) before it will resume from the +** wait. If the timeout has a value of PR_INTERVAL_NO_WAIT, the effect +** is to release the lock, possibly causing a rescheduling within the +** runtime, then immediately attempting to reacquire the lock and resume. +** +** Any other value for timeout will cause the thread to be rescheduled +** either due to explicit notification or an expired interval. The latter +** must be determined by treating time as one part of the monitored data +** being protected by the lock and tested explicitly for an expired +** interval. +** +** Returns PR_FAILURE if the caller has not locked the lock associated +** with the condition variable or the thread was interrupted (PR_Interrupt()). +** The particular reason can be extracted with PR_GetError(). +*/ +PR_IMPLEMENT(PRStatus) + PR_WaitCondVar (PRCondVar *cvar, PRIntervalTime timeout) +{ + status_t err; + if( timeout == PR_INTERVAL_NO_WAIT ) + { + PR_Unlock( cvar->lock ); + PR_Lock( cvar->lock ); + return PR_SUCCESS; + } + + if( atomic_add( &cvar->signalBenCount, 1 ) > 0 ) + { + if (acquire_sem(cvar->signalSem) == B_INTERRUPTED) + { + atomic_add( &cvar->signalBenCount, -1 ); + return PR_FAILURE; + } + } + cvar->nw += 1; + if( atomic_add( &cvar->signalBenCount, -1 ) > 1 ) + { + release_sem_etc(cvar->signalSem, 1, B_DO_NOT_RESCHEDULE); + } + + PR_Unlock( cvar->lock ); + if( timeout==PR_INTERVAL_NO_TIMEOUT ) + { + err = acquire_sem(cvar->sem); + } + else + { + err = acquire_sem_etc(cvar->sem, 1, B_RELATIVE_TIMEOUT, PR_IntervalToMicroseconds(timeout) ); + } + + if( atomic_add( &cvar->signalBenCount, 1 ) > 0 ) + { + while (acquire_sem(cvar->signalSem) == B_INTERRUPTED); + } + + if (cvar->ns > 0) + { + release_sem_etc(cvar->handshakeSem, 1, B_DO_NOT_RESCHEDULE); + cvar->ns -= 1; + } + cvar->nw -= 1; + if( atomic_add( &cvar->signalBenCount, -1 ) > 1 ) + { + release_sem_etc(cvar->signalSem, 1, B_DO_NOT_RESCHEDULE); + } + + PR_Lock( cvar->lock ); + if(err!=B_NO_ERROR) + { + return PR_FAILURE; + } + return PR_SUCCESS; +} + +/* +** Notify ONE thread that is currently waiting on 'cvar'. Which thread is +** dependent on the implementation of the runtime. Common sense would dictate +** that all threads waiting on a single condition have identical semantics, +** therefore which one gets notified is not significant. +** +** The calling thead must hold the lock that protects the condition, as +** well as the invariants that are tightly bound to the condition, when +** notify is called. +** +** Returns PR_FAILURE if the caller has not locked the lock associated +** with the condition variable. +*/ +PR_IMPLEMENT(PRStatus) + PR_NotifyCondVar (PRCondVar *cvar) +{ + status_t err ; + if( atomic_add( &cvar->signalBenCount, 1 ) > 0 ) + { + if (acquire_sem(cvar->signalSem) == B_INTERRUPTED) + { + atomic_add( &cvar->signalBenCount, -1 ); + return PR_FAILURE; + } + } + if (cvar->nw > cvar->ns) + { + cvar->ns += 1; + release_sem_etc(cvar->sem, 1, B_DO_NOT_RESCHEDULE); + if( atomic_add( &cvar->signalBenCount, -1 ) > 1 ) + { + release_sem_etc(cvar->signalSem, 1, B_DO_NOT_RESCHEDULE); + } + + while (acquire_sem(cvar->handshakeSem) == B_INTERRUPTED) + { + err = B_INTERRUPTED; + } + } + else + { + if( atomic_add( &cvar->signalBenCount, -1 ) > 1 ) + { + release_sem_etc(cvar->signalSem, 1, B_DO_NOT_RESCHEDULE); + } + } + return PR_SUCCESS; +} + +/* +** Notify all of the threads waiting on the condition variable. The order +** that the threads are notified is indeterminant. The lock that protects +** the condition must be held. +** +** Returns PR_FAILURE if the caller has not locked the lock associated +** with the condition variable. +*/ +PR_IMPLEMENT(PRStatus) + PR_NotifyAllCondVar (PRCondVar *cvar) +{ + int32 handshakes; + status_t err = B_OK; + + if( atomic_add( &cvar->signalBenCount, 1 ) > 0 ) + { + if (acquire_sem(cvar->signalSem) == B_INTERRUPTED) + { + atomic_add( &cvar->signalBenCount, -1 ); + return PR_FAILURE; + } + } + + if (cvar->nw > cvar->ns) + { + handshakes = cvar->nw - cvar->ns; + cvar->ns = cvar->nw; + release_sem_etc(cvar->sem, handshakes, B_DO_NOT_RESCHEDULE); + if( atomic_add( &cvar->signalBenCount, -1 ) > 1 ) + { + release_sem_etc(cvar->signalSem, 1, B_DO_NOT_RESCHEDULE); + } + + while (acquire_sem_etc(cvar->handshakeSem, handshakes, 0, 0) == B_INTERRUPTED) + { + err = B_INTERRUPTED; + } + } + else + { + if( atomic_add( &cvar->signalBenCount, -1 ) > 1 ) + { + release_sem_etc(cvar->signalSem, 1, B_DO_NOT_RESCHEDULE); + } + } + return PR_SUCCESS; +} |