/* Shared Memory Lock Routines
|
/* Shared Memory Lock Routines
|
*
|
*
|
* This shared memory locked queue support routine need to be
|
* This shared memory locked queue support routine need to be
|
* able to lock the specified locked queue. Interrupts are
|
* able to lock the specified locked queue. Interrupts are
|
* disabled while the queue is locked to prevent preemption
|
* disabled while the queue is locked to prevent preemption
|
* and deadlock when two tasks poll for the same lock.
|
* and deadlock when two tasks poll for the same lock.
|
* previous level.
|
* previous level.
|
*
|
*
|
* COPYRIGHT (c) 1989-1999.
|
* COPYRIGHT (c) 1989-1999.
|
* On-Line Applications Research Corporation (OAR).
|
* On-Line Applications Research Corporation (OAR).
|
*
|
*
|
* The license and distribution terms for this file may be
|
* The license and distribution terms for this file may be
|
* found in the file LICENSE in this distribution or at
|
* found in the file LICENSE in this distribution or at
|
* http://www.OARcorp.com/rtems/license.html.
|
* http://www.OARcorp.com/rtems/license.html.
|
*
|
*
|
* $Id: lock.c,v 1.2 2001-09-27 12:00:27 chris Exp $
|
* $Id: lock.c,v 1.2 2001-09-27 12:00:27 chris Exp $
|
*/
|
*/
|
|
|
#include <rtems.h>
|
#include <rtems.h>
|
#include <bsp.h>
|
#include <bsp.h>
|
#include <shm_driver.h>
|
#include <shm_driver.h>
|
|
|
/*
|
/*
|
* Shm_Initialize_lock
|
* Shm_Initialize_lock
|
*
|
*
|
* Initialize the lock for the specified locked queue.
|
* Initialize the lock for the specified locked queue.
|
*/
|
*/
|
|
|
void Shm_Initialize_lock(
|
void Shm_Initialize_lock(
|
Shm_Locked_queue_Control *lq_cb
|
Shm_Locked_queue_Control *lq_cb
|
)
|
)
|
{
|
{
|
lq_cb->lock = LQ_UNLOCKED;
|
lq_cb->lock = LQ_UNLOCKED;
|
}
|
}
|
|
|
/* void _Shm_Lock( &lq_cb )
|
/* void _Shm_Lock( &lq_cb )
|
*
|
*
|
* This shared memory locked queue support routine locks the
|
* This shared memory locked queue support routine locks the
|
* specified locked queue. It disables interrupts to prevent
|
* specified locked queue. It disables interrupts to prevent
|
* a deadlock condition.
|
* a deadlock condition.
|
*/
|
*/
|
|
|
void Shm_Lock(
|
void Shm_Lock(
|
Shm_Locked_queue_Control *lq_cb
|
Shm_Locked_queue_Control *lq_cb
|
)
|
)
|
{
|
{
|
rtems_unsigned32 isr_level;
|
rtems_unsigned32 isr_level;
|
rtems_unsigned32 *lockptr = (rtems_unsigned32 *) &lq_cb->lock;
|
rtems_unsigned32 *lockptr = (rtems_unsigned32 *) &lq_cb->lock;
|
rtems_unsigned32 lock_value;
|
rtems_unsigned32 lock_value;
|
|
|
lock_value = 0x80000000;
|
lock_value = 0x80000000;
|
rtems_interrupt_disable( isr_level );
|
rtems_interrupt_disable( isr_level );
|
|
|
Shm_isrstat = isr_level;
|
Shm_isrstat = isr_level;
|
while ( lock_value ) {
|
while ( lock_value ) {
|
asm volatile( ""
|
asm volatile( ""
|
: "=r" (lockptr), "=r" (lock_value)
|
: "=r" (lockptr), "=r" (lock_value)
|
: "0" (lockptr), "1" (lock_value)
|
: "0" (lockptr), "1" (lock_value)
|
);
|
);
|
/*
|
/*
|
* If not available, then may want to delay to reduce load on lock.
|
* If not available, then may want to delay to reduce load on lock.
|
*/
|
*/
|
|
|
if ( lock_value )
|
if ( lock_value )
|
delay( 10 ); /* approximately 10 microseconds */
|
delay( 10 ); /* approximately 10 microseconds */
|
}
|
}
|
}
|
}
|
|
|
/*
|
/*
|
* Shm_Unlock
|
* Shm_Unlock
|
*
|
*
|
* Unlock the lock for the specified locked queue.
|
* Unlock the lock for the specified locked queue.
|
*/
|
*/
|
|
|
void Shm_Unlock(
|
void Shm_Unlock(
|
Shm_Locked_queue_Control *lq_cb
|
Shm_Locked_queue_Control *lq_cb
|
)
|
)
|
{
|
{
|
rtems_unsigned32 isr_level;
|
rtems_unsigned32 isr_level;
|
|
|
lq_cb->lock = SHM_UNLOCK_VALUE;
|
lq_cb->lock = SHM_UNLOCK_VALUE;
|
isr_level = Shm_isrstat;
|
isr_level = Shm_isrstat;
|
rtems_interrupt_enable( isr_level );
|
rtems_interrupt_enable( isr_level );
|
}
|
}
|
|
|
|
|