NAME
pthread_rwlock_wrlock(), pthread_rwlock_trywrlock() — lock or attempt to lock a read-write lock for writing
SYNOPSIS
#include <pthread.h>
int pthread_rwlock_wrlock(
pthread_rwlock_t *rwlock
);
int pthread_rwlock_trywrlock(
pthread_rwlock_t *rwlock
);
PARAMETERS
- rwlock
Pointer to the read-write lock to be locked for writing.
DESCRIPTION
The
pthread_rwlock_wrlock()
function applies a write lock to the read-write lock object referenced by
rwlock.
The calling thread acquires the write lock if no other thread (reader or
writer) holds the read-write lock
rwlock.
Otherwise, the thread blocks (that is, it does not return from the
pthread_rwlock_wrlock()
call) until it can acquire the lock.
Results are undefined if the calling thread holds the read-write lock
(whether a read or a write lock) at the time the call is made.
The function
pthread_rwlock_trywrlock()
applies a write lock as in the
pthread_rwlock_wrlock()
function with the exception that the function fails if any thread currently
holds
rwlock
(for reading or writing).
Results are undefined if any of these functions are called with an
uninitialized read-write lock.
If a signal is delivered to a thread waiting for a read-write lock, upon
return from the signal handler, the thread shall resume waiting for the
read-write lock as if it was not interrupted.
RETURN VALUE
Upon successful completion,
pthread_rwlock_wrlock()
and
pthread_rwlock_trywrlock()
return zero. Otherwise, an error number is returned to indicate the error
(the
errno
variable is not set).
ERRORS
If any of the following occur, the
pthread_rwlock_trywrlock()
function returns the corresponding error number:
- [EBUSY]
The read-write lock
rwlock
could not be acquired for writing because it was already
locked for reading or writing.
For each of the following conditions, if the condition is detected, the
pthread_rwlock_wrlock()
and
pthread_rwlock_trywrlock()
functions return the corresponding error number:
- [EINVAL]
The value specified by
rwlock
does not refer to an initialized read-write lock.
- [EDEADLK]
The current thread already owns the read-write lock for reading or writing.
AUTHOR
pthread_rwlock_wrlock()
and
pthread_rwlock_trywrlock()
were developed by X/Open.
STANDARDS CONFORMANCE
pthread_rwlock_wrlock(): X/Open.
pthread_rwlock_trywrlock(): X/Open.
Printable version
