Tribblix: manual page: pthread_rwlock

PTHREAD_RWLOCK_WRLOCK(3C) Standard C Library Functions

NAME

pthread_rwlock_wrlock, pthread_rwlock_trywrlock - lock or attempt to
lock read-write lock object for writing

SYNOPSIS

cc -mt [ flag... ] file... -lpthread [ library... ]
#include <pthread.h>

int pthread_rwlock_wrlock(pthread_rwlock_t *rwlock);

int pthread_rwlock_trywrlock(pthread_rwlock_t *rwlock);

DESCRIPTION

The pthread_rwlock_wrlock() function applies a write lock to the
read-write lock 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 until it can acquire the
lock.

The pthread_rwlock_trywrlock() function applies a write lock like the
pthread_rwlock_wrlock() function, with the exception that the
function fails if any thread currently holds rwlock (for reading or
writing).

Writers are favored over readers of the same priority to avoid writer
starvation. See pthread_rwlock_rdlock(3C).

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
for writing, upon return from the signal handler the thread resumes
waiting for the read-write lock for writing as if it was not
interrupted.

RETURN VALUES

If successful, the pthread_rwlock_wrlock() function returns 0.
Otherwise, an error number is returned to indicate the error.

The pthread_rwlock_trywrlock() function returns 0 if the lock for
writing on the read-write lock object referenced by rwlock is
acquired. Otherwise an error number is returned to indicate the
error.

ERRORS

The pthread_rwlock_wrlock() function will fail if:

EDEADLK
The current thread already owns the read-write lock for
writing or reading.

The pthread_rwlock_trywrlock() function will fail if:

EBUSY
The read-write lock could not be acquired for writing
because it was already locked for reading or writing.