PTHREADRWLOCKWRLOCK(3) BSD Library Functions Manual PTHREADRWLOCKWRLOCK(3)

NAME
     pthreadrwlockwrlock, pthreadrwlocktrywrlock -- acquire a read/write
     lock for writing

SYNOPSIS
     ##include <>

     int
     pthreadrwlockwrlock(pthreadrwlockt *lock);

     int
     pthreadrwlocktrywrlock(pthreadrwlockt *lock);

DESCRIPTION
     The pthreadrwlockwrlock() function blocks until a write lock can be
     acquired against lock.  The pthreadrwlocktrywrlock() 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 pthreadrwlockwrlock() and pthreadrwlocktrywrlock()
     functions will return zero.  Otherwise an error number will be returned
     to indicate the error.

SEE ALSO
     pthreadrwlocktrywrlock(3), pthreadrwlockunlock(3),
     pthreadrwlockwrlock(3)

STANDARDS
     The pthreadrwlockwrlock() and pthreadrwlocktrywrlock() functions are
     expected to conform to Version 2 of the Single UNIX Specification
     (``SUSv2'').

ERORS
     The pthreadrwlocktrywrlock() function will fail if:

     [EBUSY]            The calling thread is not able to acquire the lock
                        without blocking.

     The pthreadrwlockwrlock() and pthreadrwlocktrywrlock() 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).

HISTORY
     The pthreadrwlockwrlock() function first appeared in FreeBSD 3.0.

BSD                             August 4, 1998                             BSD