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[/] [openrisc/] [trunk/] [rtos/] [rtems/] [c/] [src/] [lib/] [libbsp/] [a29k/] [portsw/] [shmsupp/] [lock.c] - Blame information for rev 594

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Line No. Rev Author Line
1 30 unneback
/*  Shared Memory Lock Routines
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 *
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 *  This shared memory locked queue support routine need to be
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 *  able to lock the specified locked queue.  Interrupts are
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 *  disabled while the queue is locked to prevent preemption
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 *  and deadlock when two tasks poll for the same lock.
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 *  previous level.
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 *
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 *  COPYRIGHT (c) 1989-1999.
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 *  On-Line Applications Research Corporation (OAR).
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 *
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 *  The license and distribution terms for this file may be
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 *  found in the file LICENSE in this distribution or at
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 *  http://www.OARcorp.com/rtems/license.html.
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 *
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 *  $Id: lock.c,v 1.2 2001-09-27 11:59:40 chris Exp $
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 */
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#include <rtems.h>
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#include <bsp.h>
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#include <shm_driver.h>
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#ifndef lint
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static char _sccsid[] = "@(#)lock.c 04/08/96     1.1\n";
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#endif
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/*
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 *  Shm_Initialize_lock
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 *
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 *  Initialize the lock for the specified locked queue.
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 */
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void Shm_Initialize_lock(
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  Shm_Locked_queue_Control *lq_cb
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)
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{
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  lq_cb->lock = LQ_UNLOCKED;
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}
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/*  void _Shm_Lock( &lq_cb )
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 *
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 *  This shared memory locked queue support routine locks the
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 *  specified locked queue.  It disables interrupts to prevent
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 *  a deadlock condition.
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 */
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void Shm_Lock(
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  Shm_Locked_queue_Control *lq_cb
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)
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{
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  rtems_unsigned32 isr_level;
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  rtems_unsigned32 *lockptr = &lq_cb->lock;
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  rtems_unsigned32 lock_value;
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  lock_value = 0x80000000;
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  rtems_interrupt_disable( isr_level );
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    Shm_isrstat = isr_level;
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    while ( lock_value ) {
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      asm volatile( ""
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                         : "=r" (lockptr), "=r" (lock_value)
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                         : "0" (lockptr),  "1" (lock_value)
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                  );
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      /*
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       *  If not available, then may want to delay to reduce load on lock.
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       */
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      if ( lock_value )
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        delay( 10 );   /* approximately 10 microseconds */
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   }
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}
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/*
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 *  Shm_Unlock
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 *
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 *  Unlock the lock for the specified locked queue.
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 */
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void Shm_Unlock(
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  Shm_Locked_queue_Control *lq_cb
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)
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{
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  rtems_unsigned32 isr_level;
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  lq_cb->lock = SHM_UNLOCK_VALUE;
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  isr_level = Shm_isrstat;
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  rtems_interrupt_enable( isr_level );
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}
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