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pthread_rwlock_trywrlock(3) [freebsd man page]

PTHREAD_RWLOCK_WRLOCK(3)				   BSD Library Functions Manual 				  PTHREAD_RWLOCK_WRLOCK(3)

pthread_rwlock_wrlock, pthread_rwlock_trywrlock -- acquire a read/write lock for writing LIBRARY
POSIX Threads Library (libpthread, -lpthread) 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 per- forms 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. BSD
August 4, 1998 BSD

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pthread_rwlock_wrlock(3C)												 pthread_rwlock_wrlock(3C)

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); 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 func- tion 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. 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. 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. See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ |MT-Level |MT-Safe | +-----------------------------+-----------------------------+ pthread_rwlock_init(3C), pthread_rwlock_unlock(3C), pthread_rwlockattr_init(3C), pthread_rwlock_rdlock(3C), attributes(5), standards(5) 23 Mar 2005 pthread_rwlock_wrlock(3C)
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