diff options
Diffstat (limited to 'c/src/lib/libbsp/i386/force386/shmsupp/lock.c')
-rw-r--r-- | c/src/lib/libbsp/i386/force386/shmsupp/lock.c | 83 |
1 files changed, 83 insertions, 0 deletions
diff --git a/c/src/lib/libbsp/i386/force386/shmsupp/lock.c b/c/src/lib/libbsp/i386/force386/shmsupp/lock.c new file mode 100644 index 0000000000..7e1b7874d1 --- /dev/null +++ b/c/src/lib/libbsp/i386/force386/shmsupp/lock.c @@ -0,0 +1,83 @@ +/* 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> + +/* + * 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. + */ + +void Shm_Lock( + Shm_Locked_queue_Control *lq_cb +) +{ + rtems_unsigned32 isr_level; + volatile rtems_unsigned32 *lockptr = &lq_cb->lock; + rtems_unsigned32 lock_value; + + lock_value = SHM_LOCK_VALUE; + rtems_interrupt_disable( isr_level ); + + Shm_isrstat = isr_level; + while ( 1 ) { + asm volatile( "lock ; xchg (%0),%1" + : "=r" (lockptr), "=r" (lock_value) + : "0" (lockptr), "1" (lock_value) + ); + if ( lock_value == SHM_UNLOCK_VALUE ) + break; + delay( 10 ); /* approximately 10 microseconds */ + } +} + +/* + * Shm_Unlock + * + * Unlock the lock for the specified locked queue. + */ + +void Shm_Unlock( + Shm_Locked_queue_Control *lq_cb +) +{ + rtems_unsigned32 isr_level; + + lq_cb->lock = SHM_UNLOCK_VALUE; + isr_level = Shm_isrstat; + rtems_interrupt_enable( isr_level ); +} + |