NetBSD-5.0.2/lib/libpthread/pthread_spin_unlock.3

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.\" $NetBSD: pthread_spin_unlock.3,v 1.8 2008/05/26 08:45:55 wiz Exp $
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.Dd May 26, 2008
.Dt PTHREAD_SPIN_UNLOCK 3
.Os
.Sh NAME
.Nm pthread_spin_unlock
.Nd release a spin lock
.Sh LIBRARY
.Lb libpthread
.Sh SYNOPSIS
.In pthread.h
.Ft int
.Fn pthread_spin_unlock "pthread_spinlock_t *lock"
.Sh DESCRIPTION
The
.Fn pthread_spin_unlock
function is used to release the read/write lock previously obtained by
.Fn pthread_spin_lock
or
.Fn pthread_spin_trylock .
.Sh RETURN VALUES
If successful, the
.Fn pthread_spin_unlock
function will return zero.
Otherwise an error number will be returned to indicate the error.
.Pp
The results are undefined if
.Fa lock
is not held by the calling thread.
.Sh ERRORS
The
.Fn pthread_spin_unlock
function may fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
The value specified by
.Fa lock
is invalid.
.El
.Sh SEE ALSO
.Xr pthread_spin_destroy 3 ,
.Xr pthread_spin_init 3 ,
.Xr pthread_spin_lock 3 ,
.Xr pthread_spin_trylock 3
.Sh STANDARDS
.Fn pthread_rwlock_unlock
conforms to
.St -p1003.1-2001 .
.Sh CAVEATS
Applications using spinlocks are vulnerable to the effects of priority
inversion.
Applications using real-time threads
.Pq Dv SCHED_FIFO , SCHED_RR
should not use these interfaces.
Outside carefully controlled environments, priority inversion with spinlocks
can lead to system deadlock.
Mutexes are preferable in nearly every possible use case.