NAME
pthread_rwlock_wrlock,
pthread_rwlock_trywrlock —
acquire a read/write lock for
writing
SYNOPSIS
#include
<pthread.h>
int
pthread_rwlock_wrlock(pthread_rwlock_t
*lock);
int
pthread_rwlock_trywrlock(pthread_rwlock_t
*lock);
DESCRIPTION
The
pthread_rwlock_wrlock()
function blocks until a write lock can be acquired against
lock. The
pthread_rwlock_trywrlock()
function performs the same action, but does not block if the lock cannot be
immediately obtained.
The results are undefined if the calling thread already holds the lock at the time the call is made.
IMPLEMENTATION NOTES
To prevent writer starvation, writers are favored over readers.
RETURN VALUES
If successful, the pthread_rwlock_wrlock()
and pthread_rwlock_trywrlock() functions will return
zero. Otherwise an error number will be returned to indicate the error.
ERRORS
The pthread_rwlock_trywrlock() function
will fail if:
- [
EBUSY] - The calling thread is not able to acquire the lock without blocking.
The pthread_rwlock_wrlock() and
pthread_rwlock_trywrlock() functions may fail
if:
- [
EDEADLK] - The calling thread already owns the read/write lock (for reading or writing).
- [
EINVAL] - The value specified by lock is invalid.
- [
ENOMEM] - Insufficient memory exists to initialize the lock (applies to statically initialized locks only).
SEE ALSO
pthread_rwlock_init(3), pthread_rwlock_rdlock(3), pthread_rwlock_tryrdlock(3), pthread_rwlock_unlock(3)
STANDARDS
The pthread_rwlock_wrlock() and
pthread_rwlock_trywrlock() functions are expected to
conform to Version 2 of the Single UNIX
Specification (“SUSv2”).
HISTORY
The pthread_rwlock_wrlock() function first
appeared in FreeBSD 3.0.