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\" $FreeBSD: src/lib/libpthread/man/pthread_mutexattr.3,v 1.8 2002/09/16 19:29:29 mini Exp $
Dd June 12, 2016
Dt PTHREAD_MUTEXATTR 3
Os
Sh NAME
Nm pthread_mutexattr_init ,
Nm pthread_mutexattr_destroy ,
Nm pthread_mutexattr_setprioceiling ,
Nm pthread_mutexattr_getprioceiling ,
Nm pthread_mutexattr_setprotocol ,
Nm pthread_mutexattr_getprotocol ,
Nm pthread_mutexattr_settype ,
Nm pthread_mutexattr_gettype ,
Nm pthread_mutexattr_getpshared ,
Nm pthread_mutexattr_setpshared
Nd mutex attribute operations
Sh LIBRARY
Lb libpthread
Sh SYNOPSIS
In pthread.h
Ft int
Fn pthread_mutexattr_init "pthread_mutexattr_t *attr"
Ft int
Fn pthread_mutexattr_destroy "pthread_mutexattr_t *attr"
Ft int
Fn pthread_mutexattr_setprioceiling \
"pthread_mutexattr_t *attr" "int prioceiling"
Ft int
Fn pthread_mutexattr_getprioceiling \
"pthread_mutexattr_t *attr" "int *prioceiling"
Ft int
Fn pthread_mutexattr_setprotocol \
"pthread_mutexattr_t *attr" "int protocol"
Ft int
Fn pthread_mutexattr_getprotocol \
"pthread_mutexattr_t *attr" "int *protocol"
Ft int
Fn pthread_mutexattr_settype "pthread_mutexattr_t *attr" "int type"
Ft int
Fn pthread_mutexattr_gettype \
"pthread_mutexattr_t * restrict attr" "int * restrict type"
Ft int
Fn pthread_mutexattr_getpshared \
"const pthread_mutexattr_t * restrict attr" "int * restrict pshared"
Ft int
Fn pthread_mutexattr_setpshared \
"pthread_mutexattr_t * attr" "int pshared"
Sh DESCRIPTION
Mutex attributes are used to specify parameters to
Fn pthread_mutex_init .
Like with thread attributes,
one attribute object can be used in multiple calls to
Xr pthread_mutex_init 3 ,
with or without modifications between calls.
Pp
The
Fn pthread_mutexattr_init
function initializes
Fa attr
with all the default mutex attributes.
Pp
The
Fn pthread_mutexattr_destroy
function destroys
Fa attr .
Pp
The
Fn pthread_mutexattr_settype
functions set the mutex
Fa type
value of the attribute.
Valid mutex types are:
Bl -tag -width "XXX" -offset 2n
It Dv PTHREAD_MUTEX_NORMAL
This type of mutex does not check for usage errors.
It will deadlock if reentered, and result in undefined behavior if a
locked mutex is unlocked by another thread.
Attempts to unlock an already unlocked
Dv PTHREAD_MUTEX_NORMAL
mutex will result in undefined behavior.
It Dv PTHREAD_MUTEX_ERRORCHECK
These mutexes do check for usage errors.
If an attempt is made to relock a
Dv PTHREAD_MUTEX_ERRORCHECK
mutex without first dropping the lock, an error will be returned.
If a thread attempts to unlock a
Dv PTHREAD_MUTEX_ERRORCHECK
mutex that is locked by another thread, an error will be returned.
If a thread attempts to unlock a
Dv PTHREAD_MUTEX_ERRORCHECK
thread that is unlocked, an error will be returned.
It Dv PTHREAD_MUTEX_RECURSIVE
These mutexes allow recursive locking.
An attempt to relock a
Dv PTHREAD_MUTEX_RECURSIVE
mutex that is already locked by the same thread succeeds.
An equivalent number of
Xr pthread_mutex_unlock 3
calls are needed before the mutex will wake another thread waiting
on this lock.
If a thread attempts to unlock a
Dv PTHREAD_MUTEX_RECURSIVE
mutex that is locked by another thread, an error will be returned.
If a thread attempts to unlock a
Dv PTHREAD_MUTEX_RECURSIVE
thread that is unlocked, an error will be returned.
Pp
It is advised that
Dv PTHREAD_MUTEX_RECURSIVE
mutexes are not used with condition variables.
This is because of the implicit unlocking done by
Xr pthread_cond_wait 3
and
Xr pthread_cond_timedwait 3 .
It Dv PTHREAD_MUTEX_DEFAULT
Also this type of mutex will cause undefined behavior if reentered.
Unlocking a
Dv PTHREAD_MUTEX_DEFAULT
mutex locked by another thread will result in undefined behavior.
Attempts to unlock an already unlocked
Dv PTHREAD_MUTEX_DEFAULT
mutex will result in undefined behavior.
Pp
This is the default mutex type for
Fn pthread_mutexattr_init .
El
Pp
The
Fn pthread_mutexattr_gettype
functions copy the type value of the attribute to the location
pointed to by the second parameter.
Pp
The
Fn pthread_mutexattr_getpshared
function obtains the value of the process-shared attribute from
the attributes object referenced by
Fa attr .
Pp
The
Fn pthread_mutexattr_setpshared
function is used to set the process-shared attribute in an initialised
attributes object referenced by
Fa attr .
Pp
The
Fn pthread_mutexattr_getprotocol
and
Fn pthread_mutexattr_setprotocol
functions shall get and set the protocol attribute of a mutex attributes
object pointed to by
Fa attr
which was previously created by the function
Fn pthread_mutexattr_init .
Pp
The
Fn pthread_mutexattr_getprioceiling
and
Fn pthread_mutexattr_setprioceiling
functions, shall get and set the priority ceiling attribute of a mutex attributes
object pointed to by
Fa attr
which was previously created by the function
Fn pthread_mutexattr_init .
Sh RETURN VALUES
If successful, these functions return 0.
Otherwise, an error number is returned to indicate the error.
Sh ERRORS
The
Fn pthread_mutexattr_init
function shall fail if:
Bl -tag -width Er
It Bq Er ENOMEM
Insufficient memory exists to initialize the mutex attributes object.
El
Pp
The
Fn pthread_mutexattr_settype
function shall fail if:
Bl -tag -width Er
It Bq Er EINVAL
The value specified either by
Fa type
or
Fa attr
is invalid.
El
Pp
No error numbers are defined for the
Fn pthread_mutexattr_destroy
and
Fn pthread_mutexattr_gettype
functions.
Pp
Fn pthread_mutexattr_setprioceiling
may fail if:
Bl -tag -width Er
It Bq Er EINVAL
Invalid value for
Fa attr ,
or invalid value for
Fa prioceiling .
El
Pp
Fn pthread_mutexattr_getprioceiling
may fail if:
Bl -tag -width Er
It Bq Er EINVAL
Invalid value for
Fa attr .
El
Pp
Fn pthread_mutexattr_setprotocol
may fail if:
Bl -tag -width Er
It Bq Er EINVAL
Invalid value for
Fa attr ,
or invalid value for
Fa protocol .
El
Pp
Fn pthread_mutexattr_getprotocol
may fail if:
Bl -tag -width Er
It Bq Er EINVAL
Invalid value for
Fa attr .
El
Pp
Fn pthread_mutexattr_getpshared
and
Fn pthread_mutexattr_setpshared
may fail if:
Bl -tag -width Er
It Bq Er EINVAL
the value specified by
Fa attr
is invalid.
El
Sh SEE ALSO
Xr pthread_mutex_init 3
Sh STANDARDS
These functions conform to
St -p1003.1-2001 .
Sh BUGS
The
Fn pthread_mutexattr_getpshared
and
Fn pthread_mutexattr_setpshared
functions are hidden by default since only thread shared attributes
are supported.

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