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/**
* @file
*
* @brief Surrender the Mutex
* @ingroup ScoreMutex
*/
/*
* 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.org/license/LICENSE.
*/
#if HAVE_CONFIG_H
#include "config.h"
#endif
#include <rtems/system.h>
#include <rtems/score/isr.h>
#include <rtems/score/coremuteximpl.h>
#include <rtems/score/thread.h>
Status_Control _CORE_mutex_Surrender(
CORE_mutex_Control *the_mutex,
Thread_queue_Context *queue_context
)
{
Thread_Control *the_thread;
Thread_Control *holder;
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 ) ) {
_ISR_lock_ISR_enable( &queue_context->Lock_context );
return STATUS_NOT_OWNER;
}
}
_CORE_mutex_Acquire_critical( the_mutex, queue_context );
/* XXX already unlocked -- not right status */
if ( !the_mutex->nest_count ) {
_CORE_mutex_Release( the_mutex, queue_context );
return 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:
_CORE_mutex_Release( the_mutex, queue_context );
return STATUS_SUCCESSFUL;
#if defined(RTEMS_POSIX_API)
case CORE_MUTEX_NESTING_IS_ERROR:
/* should never occur */
_CORE_mutex_Release( the_mutex, queue_context );
return STATUS_NESTING_NOT_ALLOWED;
#endif
case CORE_MUTEX_NESTING_BLOCKS:
/* Currently no API exercises this behavior. */
break;
}
#else
_CORE_mutex_Release( the_mutex, queue_context );
/* must be CORE_MUTEX_NESTING_ACQUIRES or we wouldn't be here */
return 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 ) ) {
holder->resource_count--;
}
the_mutex->holder = NULL;
/*
* Now we check if another thread was waiting for this mutex. If so,
* transfer the mutex to that thread.
*/
if (
( the_thread = _Thread_queue_First_locked(
&the_mutex->Wait_queue,
the_mutex->operations
)
)
) {
bool unblock;
the_mutex->holder = the_thread;
the_mutex->nest_count = 1;
/*
* We must extract the thread now since this will restore its default
* thread lock. This is necessary to avoid a deadlock in the
* _Thread_Change_priority() below due to a recursive thread queue lock
* acquire.
*/
unblock = _Thread_queue_Extract_locked(
&the_mutex->Wait_queue.Queue,
the_mutex->operations,
the_thread,
queue_context
);
#if defined(RTEMS_MULTIPROCESSING)
if ( _Objects_Is_local_id( the_thread->Object.id ) )
#endif
{
switch ( the_mutex->Attributes.discipline ) {
case CORE_MUTEX_DISCIPLINES_FIFO:
case CORE_MUTEX_DISCIPLINES_PRIORITY:
break;
case CORE_MUTEX_DISCIPLINES_PRIORITY_INHERIT:
the_thread->resource_count++;
_Thread_queue_Boost_priority( &the_mutex->Wait_queue.Queue, the_thread );
break;
case CORE_MUTEX_DISCIPLINES_PRIORITY_CEILING:
the_thread->resource_count++;
_Thread_Raise_priority(
the_thread,
the_mutex->Attributes.priority_ceiling
);
break;
}
}
_Thread_queue_Unblock_critical(
unblock,
&the_mutex->Wait_queue.Queue,
the_thread,
&queue_context->Lock_context
);
} else {
_CORE_mutex_Release( the_mutex, queue_context );
}
/*
* 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 ( !_Thread_Owns_resources( holder ) ) {
/*
* Ensure that the holder resource count is visible to all other processors
* and that we read the latest priority restore hint.
*/
_Atomic_Fence( ATOMIC_ORDER_ACQ_REL );
if ( holder->priority_restore_hint ) {
Per_CPU_Control *cpu_self;
cpu_self = _Thread_Dispatch_disable();
_Thread_Restore_priority( holder );
_Thread_Dispatch_enable( cpu_self );
}
}
return STATUS_SUCCESSFUL;
}
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