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