diff options
Diffstat (limited to 'linuxthreads/condvar.c')
| -rw-r--r-- | linuxthreads/condvar.c | 341 |
1 files changed, 341 insertions, 0 deletions
diff --git a/linuxthreads/condvar.c b/linuxthreads/condvar.c new file mode 100644 index 0000000..6ab95b8 --- /dev/null +++ b/linuxthreads/condvar.c @@ -0,0 +1,341 @@ +/* Linuxthreads - a simple clone()-based implementation of Posix */ +/* threads for Linux. */ +/* Copyright (C) 1996 Xavier Leroy (Xavier.Leroy@inria.fr) */ +/* and Pavel Krauz (krauz@fsid.cvut.cz). */ +/* */ +/* 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. */ + +/* Condition variables */ + +#include <errno.h> +#include <sched.h> +#include <stddef.h> +#include <sys/time.h> +#include "pthread.h" +#include "internals.h" +#include "spinlock.h" +#include "queue.h" +#include "restart.h" +#include <shlib-compat.h> + +int __pthread_cond_init(pthread_cond_t *cond, + const pthread_condattr_t *cond_attr) +{ + __pthread_init_lock(&cond->__c_lock); + cond->__c_waiting = NULL; + return 0; +} +versioned_symbol (libpthread, __pthread_cond_init, pthread_cond_init, + GLIBC_2_3_2); +#if SHLIB_COMPAT(libpthread, GLIBC_2_0, GLIBC_2_3_2) +strong_alias (__pthread_cond_init, __old_pthread_cond_init) +compat_symbol (libpthread, __old_pthread_cond_init, pthread_cond_init, + GLIBC_2_0); +#endif + +int __pthread_cond_destroy(pthread_cond_t *cond) +{ + if (cond->__c_waiting != NULL) return EBUSY; + return 0; +} +versioned_symbol (libpthread, __pthread_cond_destroy, pthread_cond_destroy, + GLIBC_2_3_2); +#if SHLIB_COMPAT(libpthread, GLIBC_2_0, GLIBC_2_3_2) +strong_alias (__pthread_cond_destroy, __old_pthread_cond_destroy) +compat_symbol (libpthread, __old_pthread_cond_destroy, pthread_cond_destroy, + GLIBC_2_0); +#endif + +/* Function called by pthread_cancel to remove the thread from + waiting on a condition variable queue. */ + +static int cond_extricate_func(void *obj, pthread_descr th) +{ + volatile pthread_descr self = thread_self(); + pthread_cond_t *cond = obj; + int did_remove = 0; + + __pthread_lock(&cond->__c_lock, self); + did_remove = remove_from_queue(&cond->__c_waiting, th); + __pthread_unlock(&cond->__c_lock); + + return did_remove; +} + +int __pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex) +{ + volatile pthread_descr self = thread_self(); + pthread_extricate_if extr; + int already_canceled = 0; + int spurious_wakeup_count; + + /* Check whether the mutex is locked and owned by this thread. */ + if (mutex->__m_kind != PTHREAD_MUTEX_TIMED_NP + && mutex->__m_kind != PTHREAD_MUTEX_ADAPTIVE_NP + && mutex->__m_owner != self) + return EINVAL; + + /* Set up extrication interface */ + extr.pu_object = cond; + extr.pu_extricate_func = cond_extricate_func; + + /* Register extrication interface */ + THREAD_SETMEM(self, p_condvar_avail, 0); + __pthread_set_own_extricate_if(self, &extr); + + /* Atomically enqueue thread for waiting, but only if it is not + canceled. If the thread is canceled, then it will fall through the + suspend call below, and then call pthread_exit without + having to worry about whether it is still on the condition variable queue. + This depends on pthread_cancel setting p_canceled before calling the + extricate function. */ + + __pthread_lock(&cond->__c_lock, self); + if (!(THREAD_GETMEM(self, p_canceled) + && THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE)) + enqueue(&cond->__c_waiting, self); + else + already_canceled = 1; + __pthread_unlock(&cond->__c_lock); + + if (already_canceled) { + __pthread_set_own_extricate_if(self, 0); + __pthread_do_exit(PTHREAD_CANCELED, CURRENT_STACK_FRAME); + } + + pthread_mutex_unlock(mutex); + + spurious_wakeup_count = 0; + while (1) + { + suspend(self); + if (THREAD_GETMEM(self, p_condvar_avail) == 0 + && (THREAD_GETMEM(self, p_woken_by_cancel) == 0 + || THREAD_GETMEM(self, p_cancelstate) != PTHREAD_CANCEL_ENABLE)) + { + /* Count resumes that don't belong to us. */ + spurious_wakeup_count++; + continue; + } + break; + } + + __pthread_set_own_extricate_if(self, 0); + + /* Check for cancellation again, to provide correct cancellation + point behavior */ + + if (THREAD_GETMEM(self, p_woken_by_cancel) + && THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE) { + THREAD_SETMEM(self, p_woken_by_cancel, 0); + pthread_mutex_lock(mutex); + __pthread_do_exit(PTHREAD_CANCELED, CURRENT_STACK_FRAME); + } + + /* Put back any resumes we caught that don't belong to us. */ + while (spurious_wakeup_count--) + restart(self); + + pthread_mutex_lock(mutex); + return 0; +} +versioned_symbol (libpthread, __pthread_cond_wait, pthread_cond_wait, + GLIBC_2_3_2); +#if SHLIB_COMPAT(libpthread, GLIBC_2_0, GLIBC_2_3_2) +strong_alias (__pthread_cond_wait, __old_pthread_cond_wait) +compat_symbol (libpthread, __old_pthread_cond_wait, pthread_cond_wait, + GLIBC_2_0); +#endif + +static int +pthread_cond_timedwait_relative(pthread_cond_t *cond, + pthread_mutex_t *mutex, + const struct timespec * abstime) +{ + volatile pthread_descr self = thread_self(); + int already_canceled = 0; + pthread_extricate_if extr; + int spurious_wakeup_count; + + /* Check whether the mutex is locked and owned by this thread. */ + if (mutex->__m_kind != PTHREAD_MUTEX_TIMED_NP + && mutex->__m_kind != PTHREAD_MUTEX_ADAPTIVE_NP + && mutex->__m_owner != self) + return EINVAL; + + /* Set up extrication interface */ + extr.pu_object = cond; + extr.pu_extricate_func = cond_extricate_func; + + /* Register extrication interface */ + THREAD_SETMEM(self, p_condvar_avail, 0); + __pthread_set_own_extricate_if(self, &extr); + + /* Enqueue to wait on the condition and check for cancellation. */ + __pthread_lock(&cond->__c_lock, self); + if (!(THREAD_GETMEM(self, p_canceled) + && THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE)) + enqueue(&cond->__c_waiting, self); + else + already_canceled = 1; + __pthread_unlock(&cond->__c_lock); + + if (already_canceled) { + __pthread_set_own_extricate_if(self, 0); + __pthread_do_exit(PTHREAD_CANCELED, CURRENT_STACK_FRAME); + } + + pthread_mutex_unlock(mutex); + + spurious_wakeup_count = 0; + while (1) + { + if (!timedsuspend(self, abstime)) { + int was_on_queue; + + /* __pthread_lock will queue back any spurious restarts that + may happen to it. */ + + __pthread_lock(&cond->__c_lock, self); + was_on_queue = remove_from_queue(&cond->__c_waiting, self); + __pthread_unlock(&cond->__c_lock); + + if (was_on_queue) { + __pthread_set_own_extricate_if(self, 0); + pthread_mutex_lock(mutex); + return ETIMEDOUT; + } + + /* Eat the outstanding restart() from the signaller */ + suspend(self); + } + + if (THREAD_GETMEM(self, p_condvar_avail) == 0 + && (THREAD_GETMEM(self, p_woken_by_cancel) == 0 + || THREAD_GETMEM(self, p_cancelstate) != PTHREAD_CANCEL_ENABLE)) + { + /* Count resumes that don't belong to us. */ + spurious_wakeup_count++; + continue; + } + break; + } + + __pthread_set_own_extricate_if(self, 0); + + /* The remaining logic is the same as in other cancellable waits, + such as pthread_join sem_wait or pthread_cond wait. */ + + if (THREAD_GETMEM(self, p_woken_by_cancel) + && THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE) { + THREAD_SETMEM(self, p_woken_by_cancel, 0); + pthread_mutex_lock(mutex); + __pthread_do_exit(PTHREAD_CANCELED, CURRENT_STACK_FRAME); + } + + /* Put back any resumes we caught that don't belong to us. */ + while (spurious_wakeup_count--) + restart(self); + + pthread_mutex_lock(mutex); + return 0; +} + +int __pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex, + const struct timespec * abstime) +{ + /* Indirect call through pointer! */ + return pthread_cond_timedwait_relative(cond, mutex, abstime); +} +versioned_symbol (libpthread, __pthread_cond_timedwait, pthread_cond_timedwait, + GLIBC_2_3_2); +#if SHLIB_COMPAT(libpthread, GLIBC_2_0, GLIBC_2_3_2) +strong_alias (__pthread_cond_timedwait, __old_pthread_cond_timedwait) +compat_symbol (libpthread, __old_pthread_cond_timedwait, + pthread_cond_timedwait, GLIBC_2_0); +#endif + +int __pthread_cond_signal(pthread_cond_t *cond) +{ + pthread_descr th; + + __pthread_lock(&cond->__c_lock, NULL); + th = dequeue(&cond->__c_waiting); + __pthread_unlock(&cond->__c_lock); + if (th != NULL) { + th->p_condvar_avail = 1; + WRITE_MEMORY_BARRIER(); + restart(th); + } + return 0; +} +versioned_symbol (libpthread, __pthread_cond_signal, pthread_cond_signal, + GLIBC_2_3_2); +#if SHLIB_COMPAT(libpthread, GLIBC_2_0, GLIBC_2_3_2) +strong_alias (__pthread_cond_signal, __old_pthread_cond_signal) +compat_symbol (libpthread, __old_pthread_cond_signal, pthread_cond_signal, + GLIBC_2_0); +#endif + +int __pthread_cond_broadcast(pthread_cond_t *cond) +{ + pthread_descr tosignal, th; + + __pthread_lock(&cond->__c_lock, NULL); + /* Copy the current state of the waiting queue and empty it */ + tosignal = cond->__c_waiting; + cond->__c_waiting = NULL; + __pthread_unlock(&cond->__c_lock); + /* Now signal each process in the queue */ + while ((th = dequeue(&tosignal)) != NULL) { + th->p_condvar_avail = 1; + WRITE_MEMORY_BARRIER(); + restart(th); + } + return 0; +} +versioned_symbol (libpthread, __pthread_cond_broadcast, pthread_cond_broadcast, + GLIBC_2_3_2); +#if SHLIB_COMPAT(libpthread, GLIBC_2_0, GLIBC_2_3_2) +strong_alias (__pthread_cond_broadcast, __old_pthread_cond_broadcast) +compat_symbol (libpthread, __old_pthread_cond_broadcast, + pthread_cond_broadcast, GLIBC_2_0); +#endif + +int __pthread_condattr_init(pthread_condattr_t *attr) +{ + return 0; +} +strong_alias (__pthread_condattr_init, pthread_condattr_init) + +int __pthread_condattr_destroy(pthread_condattr_t *attr) +{ + return 0; +} +strong_alias (__pthread_condattr_destroy, pthread_condattr_destroy) + +int pthread_condattr_getpshared (const pthread_condattr_t *attr, int *pshared) +{ + *pshared = PTHREAD_PROCESS_PRIVATE; + return 0; +} + +int pthread_condattr_setpshared (pthread_condattr_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; +} |