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[/] [openrisc/] [trunk/] [rtos/] [rtems/] [c/] [src/] [lib/] [libbsp/] [m68k/] [mvme147s/] [shmsupp/] [lock.c] - Rev 593
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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.OARcorp.com/rtems/license.html. * * $Id: lock.c,v 1.2 2001-09-27 12:00:17 chris Exp $ */ #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. */ void Shm_Lock( Shm_Locked_queue_Control *lq_cb ) { rtems_unsigned32 isr_level; rtems_unsigned32 *lockptr = (rtems_unsigned32 *)&lq_cb->lock; rtems_interrupt_disable( isr_level ); Shm_isrstat = isr_level; asm volatile( "lockit:" : : ); asm volatile( "tas %0@" : "=a" (lockptr) : "0" (lockptr) ); asm volatile( "bne lockit" : : ); /* should delay */ } /* * 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 ); }
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