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/*
* Mutex Handler
*
* DESCRIPTION:
*
* This package is the implementation of the Mutex Handler.
* This handler provides synchronization and mutual exclusion capabilities.
*
* COPYRIGHT (c) 1989-2006.
* On-Line Applications Research Corporation (OAR).
*
* The license and distribution terms for this file may be
* found in the file LICENSE in this distribution or at
* http://www.rtems.com/license/LICENSE.
*
* $Id$
*/
#if HAVE_CONFIG_H
#include "config.h"
#endif
#include <rtems/system.h>
#include <rtems/score/isr.h>
#include <rtems/score/coremutex.h>
#include <rtems/score/states.h>
#include <rtems/score/thread.h>
#include <rtems/score/threadq.h>
/*
* _CORE_mutex_Surrender
*
* DESCRIPTION:
*
* This routine frees a unit to the mutex. If a task was blocked waiting for
* a unit from this mutex, then that task will be readied and the unit
* given to that task. Otherwise, the unit will be returned to the mutex.
*
* Input parameters:
* the_mutex - the mutex to be flushed
* id - id of parent mutex
* api_mutex_mp_support - api dependent MP support actions
*
* Output parameters:
* CORE_MUTEX_STATUS_SUCCESSFUL - if successful
* core error code - if unsuccessful
*/
CORE_mutex_Status _CORE_mutex_Surrender(
CORE_mutex_Control *the_mutex,
#if defined(RTEMS_MULTIPROCESSING)
Objects_Id id,
CORE_mutex_API_mp_support_callout api_mutex_mp_support
#else
Objects_Id id __attribute__((unused)),
CORE_mutex_API_mp_support_callout api_mutex_mp_support __attribute__((unused))
#endif
)
{
Thread_Control *the_thread;
Thread_Control *holder;
#ifdef __RTEMS_STRICT_ORDER_MUTEX__
Chain_Node *first_node;
#endif
holder = the_mutex->holder;
/*
* The following code allows a thread (or ISR) other than the thread
* which acquired the mutex to release that mutex. This is only
* allowed when the mutex in quetion is FIFO or simple Priority
* discipline. But Priority Ceiling or Priority Inheritance mutexes
* must be released by the thread which acquired them.
*/
if ( the_mutex->Attributes.only_owner_release ) {
if ( !_Thread_Is_executing( holder ) )
return CORE_MUTEX_STATUS_NOT_OWNER_OF_RESOURCE;
}
/* XXX already unlocked -- not right status */
if ( !the_mutex->nest_count )
return CORE_MUTEX_STATUS_SUCCESSFUL;
the_mutex->nest_count--;
if ( the_mutex->nest_count != 0 ) {
/*
* All error checking is on the locking side, so if the lock was
* allowed to acquired multiple times, then we should just deal with
* that. The RTEMS_DEBUG is just a validation.
*/
#if defined(RTEMS_DEBUG)
switch ( the_mutex->Attributes.lock_nesting_behavior ) {
case CORE_MUTEX_NESTING_ACQUIRES:
return CORE_MUTEX_STATUS_SUCCESSFUL;
case CORE_MUTEX_NESTING_IS_ERROR:
/* should never occur */
return CORE_MUTEX_STATUS_NESTING_NOT_ALLOWED;
case CORE_MUTEX_NESTING_BLOCKS:
/* Currently no API exercises this behavior. */
break;
}
#else
/* must be CORE_MUTEX_NESTING_ACQUIRES or we wouldn't be here */
return CORE_MUTEX_STATUS_SUCCESSFUL;
#endif
}
/*
* Formally release the mutex before possibly transferring it to a
* blocked thread.
*/
if ( _CORE_mutex_Is_inherit_priority( &the_mutex->Attributes ) ||
_CORE_mutex_Is_priority_ceiling( &the_mutex->Attributes ) ){
#ifdef __RTEMS_STRICT_ORDER_MUTEX__
/*Check whether the holder release the mutex in LIFO order
if not return error code*/
if(holder->lock_mutex.first != &the_mutex->queue.lock_queue){
the_mutex->nest_count++;
return CORE_MUTEX_RELEASE_NOT_ORDER;
}
first_node = _Chain_Get_first_unprotected(&holder->lock_mutex);
#endif
holder->resource_count--;
}
the_mutex->holder = NULL;
the_mutex->holder_id = 0;
/*
* Whether or not someone is waiting for the mutex, an
* inherited priority must be lowered if this is the last
* mutex (i.e. resource) this task has.
*/
if ( _CORE_mutex_Is_inherit_priority( &the_mutex->Attributes ) ||
_CORE_mutex_Is_priority_ceiling( &the_mutex->Attributes ) ) {
#ifdef __RTEMS_STRICT_ORDER_MUTEX__
if(the_mutex->queue.priority_before != holder->current_priority)
_Thread_Change_priority(holder,the_mutex->queue.priority_before,true);
#endif
if ( holder->resource_count == 0 &&
holder->real_priority != holder->current_priority ) {
_Thread_Change_priority( holder, holder->real_priority, true );
}
}
/*
* Now we check if another thread was waiting for this mutex. If so,
* transfer the mutex to that thread.
*/
if ( ( the_thread = _Thread_queue_Dequeue( &the_mutex->Wait_queue ) ) ) {
#if defined(RTEMS_MULTIPROCESSING)
if ( !_Objects_Is_local_id( the_thread->Object.id ) ) {
the_mutex->holder = NULL;
the_mutex->holder_id = the_thread->Object.id;
the_mutex->nest_count = 1;
( *api_mutex_mp_support)( the_thread, id );
} else
#endif
{
the_mutex->holder = the_thread;
the_mutex->holder_id = the_thread->Object.id;
the_mutex->nest_count = 1;
switch ( the_mutex->Attributes.discipline ) {
case CORE_MUTEX_DISCIPLINES_FIFO:
case CORE_MUTEX_DISCIPLINES_PRIORITY:
break;
case CORE_MUTEX_DISCIPLINES_PRIORITY_INHERIT:
#ifdef __RTEMS_STRICT_ORDER_MUTEX__
_Chain_Prepend_unprotected(&the_thread->lock_mutex,&the_mutex->queue.lock_queue);
the_mutex->queue.priority_before = the_thread->current_priority;
#endif
the_thread->resource_count++;
break;
case CORE_MUTEX_DISCIPLINES_PRIORITY_CEILING:
#ifdef __RTEMS_STRICT_ORDER_MUTEX__
_Chain_Prepend_unprotected(&the_thread->lock_mutex,&the_mutex->queue.lock_queue);
the_mutex->queue.priority_before = the_thread->current_priority;
#endif
the_thread->resource_count++;
if (the_mutex->Attributes.priority_ceiling <
the_thread->current_priority){
_Thread_Change_priority(
the_thread,
the_mutex->Attributes.priority_ceiling,
false
);
}
break;
}
}
} else
the_mutex->lock = CORE_MUTEX_UNLOCKED;
return CORE_MUTEX_STATUS_SUCCESSFUL;
}
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