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

NAME
     pptthhrreeaaddrrwwlloocckkwwrrlloocckk, pptthhrreeaaddrrwwlloocckkttrryywwrrlloocckk - acquire a read/write
     lock for writing

SYNOPSIS
     ##iinncclluuddee <>

     int
     pptthhrreeaaddrrwwlloocckkwwrrlloocckk(pthreadrwlockt *lock);

     int
     pptthhrreeaaddrrwwlloocckkttrryywwrrlloocckk(pthreadrwlockt *lock);

DESCRIPTION
     The pptthhrreeaaddrrwwlloocckkwwrrlloocckk() function blocks until a write lock can be
     acquired against lock.  The pptthhrreeaaddrrwwlloocckkttrryywwrrlloocckk() 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.

IIMMPPLLEEMMEENNTTAATTIIOONN NNOOTTEESS
     To prevent writer starvation, writers are favored over readers.

RETURN VALUES
     If successful, the pptthhrreeaaddrrwwlloocckkwwrrlloocckk() and pptthhrreeaaddrrwwlloocckkttrryywwrrlloocckk()
     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 pptthhrreeaaddrrwwlloocckkwwrrlloocckk() and pptthhrreeaaddrrwwlloocckkttrryywwrrlloocckk() functions are
     expected to conform to Version 2 of the Single UNIX Specification
     (``SUSv2'').

EERRRROORRSS
     The pptthhrreeaaddrrwwlloocckkttrryywwrrlloocckk() function will fail if:

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

     The pptthhrreeaaddrrwwlloocckkwwrrlloocckk() and pptthhrreeaaddrrwwlloocckkttrryywwrrlloocckk() 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 pptthhrreeaaddrrwwlloocckkwwrrlloocckk() function first appeared in FreeBSD 3.0.

BSD                             August 4, 1998                             BSD