path: root/static/openbsd/man3/pthread_mutex_init.3

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.\" $FreeBSD: pthread_mutex_init.3,v 1.6 1999/08/28 00:03:07 peter Exp $
.\" $FreeBSD: pthread_mutex_destroy.3,v 1.5 1999/08/28 00:03:07 peter Exp $
.\" $FreeBSD: pthread_mutex_lock.3,v 1.5 1999/08/28 00:03:07 peter Exp $
.\" $FreeBSD: pthread_mutex_unlock.3,v 1.5 1999/08/28 00:03:08 peter Exp $
.\"
.Dd $Mdocdate: July 25 2025 $
.Dt PTHREAD_MUTEX_INIT 3
.Os
.Sh NAME
.Nm pthread_mutex_init ,
.Nm pthread_mutex_destroy ,
.Nm pthread_mutex_lock ,
.Nm pthread_mutex_timedlock ,
.Nm pthread_mutex_trylock ,
.Nm pthread_mutex_unlock
.Nd operations on mutex variables
.Sh SYNOPSIS
.Lb libpthread
.In pthread.h
.Ft int
.Fo pthread_mutex_init
.Fa "pthread_mutex_t *mutex"
.Fa "const pthread_mutexattr_t *attr"
.Fc
.Ft int
.Fo pthread_mutex_destroy
.Fa "pthread_mutex_t *mutex"
.Fc
.Ft int
.Fo pthread_mutex_lock
.Fa "pthread_mutex_t *mutex"
.Fc
.Ft int
.Fo pthread_mutex_timedlock
.Fa "pthread_mutex_t *mutex"
.Fa "const struct timespec *abstime"
.Fc
.Ft int
.Fo pthread_mutex_trylock
.Fa "pthread_mutex_t *mutex"
.Fc
.Ft int
.Fo pthread_mutex_unlock
.Fa "pthread_mutex_t *mutex"
.Fc
.Sh DESCRIPTION
The
.Fn pthread_mutex_init
function creates a new mutex, with attributes specified with
.Fa attr .
If
.Fa attr
is
.Dv NULL
the default attributes are used, otherwise
.Fa attr
should be initialized by calling
.Xr pthread_mutexattr_init 3 .
.Pp
A mutex may also be initialized by assignment with the macro
PTHREAD_MUTEX_INITIALIZER.
.Pp
The
.Fn pthread_mutex_destroy
function frees the resources allocated for
.Fa mutex .
.Pp
The
.Fn pthread_mutex_lock
function locks
.Fa mutex .
If the mutex is currently locked by another thread,
the calling thread will block until the
mutex becomes available.
.Pp
If the mutex is currently locked by the calling thread,
then the behavior depends on the type of the mutex.
If
.Fa mutex
is of type
.Dv PTHREAD_MUTEX_NORMAL ,
then the calling thread will deadlock and never return from
.Fn pthread_mutex_lock .
If
.Fa mutex
is of type
.Dv PTHREAD_MUTEX_ERRORCHECK ,
then
.Er EDEADLK
is immediately returned.
If
.Fa mutex
is of type
.Dv PTHREAD_MUTEX_RECURSIVE ,
then the recursion count on the mutex is incremented.
.Pp
The
.Fn pthread_mutex_timedlock
function locks
.Fa mutex
like
.Fn pthread_mutex_lock
except that it will not block or deadlock past the system time
specified in
.Fa abstime .
.Pp
The
.Fn pthread_mutex_trylock
function locks
.Fa mutex
like
.Fn pthread_mutex_lock
except that if
.Fa mutex
is locked by another thread,
or is locked by the calling thread and is not of type
.Dv PTHREAD_MUTEX_RECURSIVE ,
then it will immediately return
.Er EBUSY .
.Pp
The
.Fn pthread_mutex_unlock
function unlocks the previously locked
.Fa mutex .
.Sh RETURN VALUES
These functions return zero for success and positive error numbers
for failure.
.Sh ERRORS
.Fn pthread_mutex_init
fails if:
.Bl -tag -width Er
.It Bq Er EINVAL
The value specified by
.Fa attr
is invalid.
.It Bq Er ENOMEM
The process cannot allocate enough memory to create another mutex.
.El
.Pp
The other functions fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
The value specified by
.Fa mutex
is invalid.
.El
.Pp
.Fn pthread_mutex_destroy
fails if:
.Bl -tag -width Er
.It Bq Er EBUSY
.Fa mutex
is locked or referenced by another thread.
.El
.Pp
.Fn pthread_mutex_lock ,
.Fn pthread_mutex_timedlock ,
and
.Fn pthread_mutex_trylock
fail if:
.Bl -tag -width Er
.It Bq Er EAGAIN
The mutex is of type
.Dv PTHREAD_MUTEX_RECURSIVE
and the maximum recursion count has been reached.
.El
.Pp
.Fn pthread_mutex_lock
and
.Fn pthread_mutex_timedlock
fail if:
.Bl -tag -width Er
.It Bq Er EDEADLK
The mutex is of type
.Dv PTHREAD_MUTEX_ERRORCHECK
and is already locked by the calling thread.
.El
.Pp
.Fn pthread_mutex_timedlock
fails if:
.Bl -tag -width Er
.It Bq Er ETIMEDOUT
The mutex could not be locked and the specified time was reached.
.El
.Pp
.Fn pthread_mutex_trylock
fails if:
.Bl -tag -width Er
.It Bq Er EBUSY
The mutex could not be locked because it was already locked.
.El
.Pp
.Fn pthread_mutex_unlock
fails if:
.Bl -tag -width Er
.It Bq Er EPERM
The current thread does not hold a lock on
.Fa mutex .
.El
.Sh SEE ALSO
.Xr pthread_mutexattr_init 3 ,
.Xr pthreads 3
.Sh STANDARDS
These functions conform to
.St -p1003.1-2024 .
Raising an error for invalid arguments is an extension.