pthread_mutexattr_setprotocol()

Set a mutex's scheduling protocol

Synopsis:

#include <pthread.h>

int pthread_mutexattr_setprotocol( 
            pthread_mutexattr * attr,
            int protocol );

Arguments:

attr
A pointer to the pthread_mutexattr_t object that you want to set the attribute in.
protocol
The new value of the scheduling protocol; one of:
  • PTHREAD_PRIO_INHERIT — when a thread is blocking higher-priority threads by locking one or more mutexes with this attribute, raise the thread's priority to that of the highest priority thread waiting on the PTHREAD_PRIO_INHERIT mutex.
  • PTHREAD_PRIO_PROTECT — execute the thread at the highest priority or priority ceilings of all the mutexes owned by the thread and initialized with PTHREAD_PRIO_PROTECT, whether other threads are blocked or not.

    In order to change the priority ceiling to a value above the maximum permitted for unprivileged processes, your process must have the PROCMGR_AID_PRIORITY ability enabled. For more information, see procmgr_ability() .

  • PTHREAD_PRIO_NONE — owning the mutex doesn't affect the priority and scheduling of the thread.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The pthread_mutexattr_setprotocol() function sets the mutex attribute attr's scheduling protocol to protocol. The structure pointed to by attr must have been previously created with pthread_mutexattr_init().

The protocol attribute defines the protocol for using mutexes. A thread holding a PTHREAD_PRIO_INHERIT mutex won't be moved to the tail of the scheduling queue if its original priority is changed (by a call to pthread_schedsetparam(), for example). This remains true if the thread unlocks the PTHREAD_PRIO_INHERIT mutex.

Returns:

EOK
Success.
ENOTSUP
The protocol argument is an unsupported or an invalid value.
EPERM
The calling process doesn't have the required permission; see procmgr_ability() .

Classification:

POSIX 1003.1 THR TPP|TPI

Safety:  
Cancellation point No
Interrupt handler No
Signal handler Yes
Thread Yes

Last modified: 2013-12-23

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