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/* Shared Memory Lock Routines
*
* This shared memory locked queue support routine need to be
* able to lock the specified locked queue. Interrupts are
* disabled while the queue is locked to prevent preemption
* and deadlock when two tasks poll for the same lock.
* previous level.
*
* COPYRIGHT (c) 1989-1999.
* 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.
*/
#include <rtems.h>
#include <bsp.h>
#include <shm_driver.h>
/*
* Shm_Initialize_lock
*
* Initialize the lock for the specified locked queue.
*/
void Shm_Initialize_lock(
Shm_Locked_queue_Control *lq_cb
)
{
lq_cb->lock = LQ_UNLOCKED;
}
/* void _Shm_Lock( &lq_cb )
*
* This shared memory locked queue support routine locks the
* specified locked queue. It disables interrupts to prevent
* a deadlock condition.
*/
__asm__ (
".text\n"
".align 4\n"
"LEON3_Atomic_Swap:\n"
" retl\n"
" swapa [%o1] 1, %o0\n"
);
void Shm_Lock(
Shm_Locked_queue_Control *lq_cb
)
{
uint32_t isr_level;
uint32_t *lockptr = (uint32_t *) &lq_cb->lock;
uint32_t lock_value;
lock_value = SHM_LOCK_VALUE;
rtems_interrupt_disable( isr_level );
Shm_isrstat = isr_level;
while ( lock_value ) {
lock_value = LEON3_Atomic_Swap(lock_value, lockptr);
/* __asm__ volatile( "" */
/* : "=r" (lockptr), "=r" (lock_value) */
/* : "0" (lockptr), "1" (lock_value) */
/* ); */
/*
* If not available, then may want to delay to reduce load on lock.
*/
/* if ( lock_value ) */
/* rtems_bsp_delay( 10 ); /\* approximately 10 microseconds *\/ */
}
}
/*
* Shm_Unlock
*
* Unlock the lock for the specified locked queue.
*/
void Shm_Unlock(
Shm_Locked_queue_Control *lq_cb
)
{
uint32_t isr_level;
lq_cb->lock = SHM_UNLOCK_VALUE;
isr_level = Shm_isrstat;
rtems_interrupt_enable( isr_level );
}
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