PTHREAD_RWLOCK_TRYWRLOCK(3) Library Functions Manual PTHREAD_RWLOCK_TRYWRLOCK(3)

pthread_rwlock_trywrlock pthread_rwlock_wrlock — lock a read-write lock object for writing

#include <pthread.h>

int pthread_rwlock_trywrlock(pthread_rwlock_t *rwlock);
int pthread_rwlock_wrlock(pthread_rwlock_t *rwlock);

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

The pthread_rwlock_wrlock () function shall apply a write lock to the read-write lock referenced by rwlock. The calling thread shall acquire the write lock if no thread (reader or writer) holds the read-write lock rwlock. Otherwise, if another thread holds the read-write lock rwlock, the calling thread shall block until it can acquire the lock. If a deadlock condition occurs or the calling thread already owns the read-write lock for writing or reading, the call shall either deadlock or return [EDEADLK].

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.

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

If successful, the pthread_rwlock_wrlock () function shall return zero; otherwise, an error number shall be returned to indicate the error.

The pthread_rwlock_trywrlock () function shall fail if:

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

The pthread_rwlock_wrlock () function may fail if:

A deadlock condition was detected or the current thread already owns the read-write lock for writing or reading.

These functions shall not return an error code of [EINTR].

None.

Applications using these functions may be subject to priority inversion, as discussed in XBD V1_chap03(7).

If an implementation detects that the value specified by the rwlock argument to pthread_rwlock_trywrlock () or pthread_rwlock_wrlock () does not refer to an initialized read-write lock object, it is recommended that the function should fail and report an [EINVAL] error.

None.

pthread_rwlock_destroy(3), pthread_rwlock_rdlock(3), pthread_rwlock_timedrdlock(3), pthread_rwlock_timedwrlock(3), pthread_rwlock_unlock(3)

XBD V1_chap03(7), V1_chap04(7), <pthread.h>

First released in Issue 5.

The following changes are made for alignment with IEEE Std 1003.1j-2000:

  • The margin code in the SYNOPSIS is changed to THR to indicate that the functionality is now part of the Threads option (previously it was part of the Read-Write Locks option in IEEE Std 1003.1j-2000 and also part of the XSI extension).
  • The [EDEADLK] error is deleted as a pthread_rwlock_trywrlock () error.
  • The SEE ALSO section is updated.

IEEE Std 1003.1-2001 (“POSIX.1”)/Cor 2-2004, item XSH/TC2/D6/104 is applied, updating the ERRORS section so that the [EDEADLK] error includes detection of a deadlock condition.

The pthread_rwlock_trywrlock () and pthread_rwlock_wrlock () functions are moved from the Threads option to the Base.

The [EINVAL] error for an uninitialized read-write lock object is removed; this condition results in undefined behavior.

POSIX.1-2008, Technical Corrigendum 2, XSH/TC2-2008/0290 [720] and XSH/TC2-2008/0291 [722] are applied.

January 31, 2018 posix.fail