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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, 1990, 1991, 1992, 1993, 1994.
* On-Line Applications Research Corporation (OAR).
* All rights assigned to U.S. Government, 1994.
*
* This material may be reproduced by or for the U.S. Government pursuant
* to the copyright license under the clause at DFARS 252.227-7013. This
* notice must appear in all copies of this file and its derivatives.
*
* $Id$
*/
#include <rtems.h>
#include <bsp.h>
#include <shm.h>
#include <errno.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <sys/sem.h>
extern int semid;
/*
* 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_cb - Shm_Locked_queues ) / sizeof( Shm_Locked_queue_Control );
}
/* Shm_Lock( &lq_cb )
*
* This shared memory locked queue support routine locks the
* specified locked queue. It disables interrupts to prevent
* a deadlock condition.
*/
void Shm_Lock(
Shm_Locked_queue_Control *lq_cb
)
{
rtems_unsigned32 isr_level;
struct sembuf sb;
int status;
isr_level = 0;
sb.sem_num = lq_cb->lock;
sb.sem_op = -1;
sb.sem_flg = 0;
rtems_interrupt_disable( isr_level );
Shm_isrstat = isr_level;
while (1) {
status = semop(semid, &sb, 1);
if ( status == 0 )
break;
if ( status == -1 && errno == EINTR )
continue;
fprintf( stderr, "shm lock (%d %d)\n", status, errno );
exit( 0 );
}
}
/*
* Shm_Unlock
*
* Unlock the lock for the specified locked queue.
*/
void Shm_Unlock(
Shm_Locked_queue_Control *lq_cb
)
{
rtems_unsigned32 isr_level;
struct sembuf sb;
int status;
isr_level = 0;
sb.sem_num = lq_cb->lock;
sb.sem_op = 1;
sb.sem_flg = 0;
while (1) {
status = semop(semid, &sb, 1);
if ( status == 0 )
break;
if ( status == -1 && errno == EINTR )
continue;
fprintf( stderr, "shm lock (%d %d)\n", status, errno ); fflush( stderr );
exit( 0 );
}
isr_level = Shm_isrstat;
rtems_interrupt_enable( isr_level );
}
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