NAME
pthread_mutex_unlock() — unlock a mutex.
SYNOPSIS
#include <pthread.h>
int pthread_mutex_unlock(
pthread_mutex_t *mutex
);
PARAMETERS
- mutex
Pointer to the mutex to be unlocked.
DESCRIPTION
The function
pthread_mutex_unlock()
is called by the owner of the mutex referenced by
mutex
to unlock the mutex.
The manner in that the mutex is released is dependent upon the mutex's
type
attribute.
For normal and default mutexes, undefined behavior will result if
pthread_mutex_unlock()
is called on an unlocked mutex or by a thread that is not the current owner.
For recursive and error-checking mutexes, an error is returned if
pthread_mutex_unlock()
is called on an unlocked mutex or by a thread which is not the current owner.
For recursive mutexes, the owner must call
pthread_mutex_unlock()
as many times as the mutex was locked before another thread can lock the mutex.
If there are threads blocked on the mutex referenced by
mutex
when
pthread_mutex_unlock()
releases the mutex, the scheduling policy is used to determine which thread
will acquire the mutex next.
RETURN VALUE
Upon successful completion,
pthread_mutex_unlock()
returns zero. Otherwise, an error number is returned to indicate the error
(the
errno
variable is not set).
ERRORS
For each of the following conditions, if the condition is detected, the
pthread_mutex_unlock()
function returns the corresponding error number:
- [EINVAL]
mutex
is not an initialized mutex.
- [EPERM]
The calling thread does not own
mutex.
On HP-UX, this error is not detected for
PTHREAD_MUTEX_FAST
or
PTHREAD_MUTEX_DEFAULT
mutexes.
- [EFAULT]
mutex
parameter points to an illegal address.
AUTHOR
pthread_mutex_unlock()
was derived from the IEEE POSIX P1003.1c standard and HP extensions.
STANDARDS CONFORMANCE
pthread_mutex_unlock(): POSIX 1003.1c.
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