source: rtems/c/src/lib/libbsp/m68k/mvme147s/shmsupp/lock.c @ afe99c2

4.104.114.84.95
Last change on this file since afe99c2 was afe99c2, checked in by Joel Sherrill <joel.sherrill@…>, on Sep 18, 1996 at 2:17:54 PM

new file submitted by Dominique le Campion.

  • Property mode set to 100644
File size: 1.7 KB
Line 
1/*  Shared Memory Lock Routines
2 *
3 *  This shared memory locked queue support routine need to be
4 *  able to lock the specified locked queue.  Interrupts are
5 *  disabled while the queue is locked to prevent preemption
6 *  and deadlock when two tasks poll for the same lock.
7 *  previous level.
8 *
9 *  COPYRIGHT (c) 1989, 1990, 1991, 1992, 1993, 1994.
10 *  On-Line Applications Research Corporation (OAR).
11 *  All rights assigned to U.S. Government, 1994.
12 *
13 *  This material may be reproduced by or for the U.S. Government pursuant
14 *  to the copyright license under the clause at DFARS 252.227-7013.  This
15 *  notice must appear in all copies of this file and its derivatives.
16 *
17 *  $Id$
18 */
19
20#include <rtems.h>
21#include <bsp.h>
22#include <shm.h>
23
24/*
25 *  Shm_Initialize_lock
26 *
27 *  Initialize the lock for the specified locked queue.
28 */
29
30void Shm_Initialize_lock(
31  Shm_Locked_queue_Control *lq_cb
32)
33{
34  lq_cb->lock = LQ_UNLOCKED;
35}
36
37/*  void _Shm_Lock( &lq_cb )
38 *
39 *  This shared memory locked queue support routine locks the
40 *  specified locked queue.  It disables interrupts to prevent
41 *  a deadlock condition.
42 */
43
44void Shm_Lock(
45  Shm_Locked_queue_Control *lq_cb
46)
47{
48  rtems_unsigned32 isr_level;
49  rtems_unsigned32 *lockptr = (rtems_unsigned32 *)&lq_cb->lock;
50
51  rtems_interrupt_disable( isr_level );
52    Shm_isrstat = isr_level;
53    asm volatile( "lockit:"    : : );
54    asm volatile( "tas %0@"    : "=a" (lockptr) : "0" (lockptr) );
55    asm volatile( "bne lockit" : : );
56/* should delay */
57}
58
59/*
60 *  Shm_Unlock
61 *
62 *  Unlock the lock for the specified locked queue.
63 */
64
65void Shm_Unlock(
66  Shm_Locked_queue_Control *lq_cb
67)
68{
69  rtems_unsigned32 isr_level;
70
71  lq_cb->lock = SHM_UNLOCK_VALUE;
72  isr_level = Shm_isrstat;
73  rtems_interrupt_enable( isr_level );
74}
75
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