pthread_mutexattr_setprotocol(PTHREAD)
pthread_mutexattr_setprotocol, pthread_mutexattr_getprotocol --
set, get protocol attribute of mutex attribute object
Synopsis
cc [options] -Kthread file
#include <pthread.h>
int pthread_mutexattr_setprotocol(pthread_mutexattr_t *attr,
int protocol);
int pthread_mutexattr_getprotocol(const pthread_mutexattr_t *attr),
int *protocol);
Description
pthread_mutexattr_setprotocol and
pthread_mutexattr_setprotocol, respectively, set
and get the protocol attribute of a mutex attribute object
pointed to by attr.
The attr parameter is a pointer to a mutex
attribute object previously created by
pthread_mutexattr_init.
*protocol defines the protocol to be followed in
utilizing mutexes.
Valid values for protocol are defined
in the header <pthread.h>, and may
be one of the following:
PTHREAD_PRIO_NONE-
When a thread owns a mutex with the
PTHREAD_PRIO_NONE protocol attribute,
its priority and scheduling are not affected by its
mutex ownership.
PTHREAD_PRIO_INHERIT-
When a thread is blocking higher priority threads because
of owning one or more mutexes with the
PTHREAD_PRIO_INHERIT protocol attribute,
it executes at the higher of its priority or
the priority of the highest priority thread waiting on any
of the mutexes owned by this thread and initialized
with this protocol.
PTHREAD_PRIO_PROTECT-
When a thread owns one or more mutexes initialized with
the PTHREAD_PRIO_PROTECT protocol,
it executes at the higher of its priority or the highest
of the priority ceilings of all the mutexes owned by
this thread and initialized with this attribute,
regardless of whether other threads are blocked on
any of these mutexes or not.
While a thread is holding a mutex which has been
initialized with the
PRIO_INHERIT or PRIO_PROTECT
protocol attributes, it will not be subject to
being moved to the tail of the scheduling queue
at its priority in the event that its original
priority is changed,
such as by a call to
sched_setparam.
Likewise, when a thread unlocks a mutex
that has been initialized with the
PRIO_INHERIT or PRIO_PROTECT
protocol attributes, it will not be subject to
being moved to the tail of the scheduling queue at its
priority in the event that its original priority is
changed.
If a thread simultaneously owns several mutexes initialized
with different protocols,
it will execute at the highest of the
priorities that it would have obtained
by each of these protocols.
When a thread makes a call to pthread_mutex_lock,
if the symbol _POSIX_THREAD_PRIO_INHERIT is
defined and the mutex was initialized with the protocol
attribute having the value PTHREAD_PRIO_INHERIT,
when the calling thread is blocked because the mutex is
owned by another thread, that owner thread will inherit
the priority level of the calling thread as long as it
continues to own the mutex.
The implementation updates its execution priority
to the maximum of its assigned priority and all its
inherited priorities.
Furthermore, if this owner thread itself becomes blocked
on another mutex, the same priority inheritance effect
will be propagated to this other owner thread,
in a recursive manner.
Return values
pthread_mutexattr_setprotocol
and pthread_mutexattr_getprotocol
return zero on success.
Otherwise, an error number is returned.
Diagnostics
pthread_mutexattr_setprotocol
and pthread_mutexattr_getprotocol
return the following value if the corresponding condition
is detected:
EINVAL-
The value specified by attr or protocol is invalid.
ENOSYS-
Neither of the options _POSIX_THREAD_PRIO_PROTECT
and _POSIX_THREAD_PRIO_INHERIT
is defined and the implementation does not
support the function.
ENOTSUP-
The value specified by protocol is an
unsupported value.
EPERM-
The caller does not have the privilege to perform the
operation.
Standards Compliance
The Single UNIX Specification, Version 2; The Open Group.
References
Intro(PTHREAD),
pthread_create(PTHREAD),
pthread_cond_init(PTHREAD),
pthread_mutex_init(PTHREAD),
pthread(F)
© 2005 The SCO Group, Inc. All rights reserved.
SCO OpenServer Release 6.0.0 - 01 June 2005