pthreads/pthread_rwlock_wrlock.3

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  27 .Dd August 4, 1998
  28 .Dt PTHREAD_RWLOCK_WRLOCK 3
  29 .Os
  30 .Sh NAME
  31 .Nm pthread_rwlock_wrlock ,
  32 .Nm pthread_rwlock_trywrlock
  33 .Nd acquire a read/write lock for writing
  34 .Sh SYNOPSIS
  35 .In pthread.h
  36 .Ft int
  37 .Fn pthread_rwlock_wrlock "pthread_rwlock_t *lock"
  38 .Ft int
  39 .Fn pthread_rwlock_trywrlock "pthread_rwlock_t *lock"
  40 .Sh DESCRIPTION
  41 The
  42 .Fn pthread_rwlock_wrlock
  43 function blocks until a write lock can be acquired against
  44 .Fa lock .
  45 The
  46 .Fn pthread_rwlock_trywrlock
  47 function performs the same action, but does not block if the lock
  48 cannot be immediately obtained.
  49 .Pp
  50 The results are undefined if the calling thread already holds the
  51 lock at the time the call is made.
  52 .Sh IMPLEMENTATION NOTES
  53 To prevent writer starvation, writers are favored over readers.
  54 .Sh RETURN VALUES
  55 If successful, the
  56 .Fn pthread_rwlock_wrlock
  57 and
  58 .Fn pthread_rwlock_trywrlock
  59 functions will return zero.  Otherwise an error number will be returned
  60 to indicate the error.
  61 .Sh SEE ALSO
  62 .Xr pthread_rwlock_trywrlock 3 ,
  63 .Xr pthread_rwlock_unlock 3 ,
  64 .Xr pthread_rwlock_wrlock 3
  65 .Sh STANDARDS
  66 The
  67 .Fn pthread_rwlock_wrlock
  68 and
  69 .Fn pthread_rwlock_trywrlock
  70 functions are expected to conform to
  71 .St -susv2 .
  72 .Sh ERRORS
  73 The
  74 .Fn pthread_rwlock_trywrlock
  75 function will fail if:
  76 .Bl -tag -width Er
  77 .It Bq Er EBUSY
  78 The calling thread is not able to acquire the lock without blocking.
  79 .El
  80 .Pp
  81 The
  82 .Fn pthread_rwlock_wrlock
  83 and
  84 .Fn pthread_rwlock_trywrlock
  85 functions may fail if:
  86 .Bl -tag -width Er
  87 .It Bq Er EDEADLK
  88 The calling thread already owns the read/write lock (for reading
  89 or writing).
  90 .It Bq Er EINVAL
  91 The value specified by
  92 .Fa lock
  93 is invalid.
  94 .It Bq Er ENOMEM
  95 Insufficient memory exists to initialize the lock (applies to
  96 statically initialized locks only).
  97 .El
  98 .Sh HISTORY
  99 The
 100 .Fn pthread_rwlock_wrlock
 101 function first appeared in
 102 .Fx 3.0 .