source: rtems/c/src/lib/libbsp/i960/cvme961/shmsupp/lock.c @ ac7d5ef0

4.104.114.84.95
Last change on this file since ac7d5ef0 was ac7d5ef0, checked in by Joel Sherrill <joel.sherrill@…>, on May 11, 1995 at 5:39:37 PM

Initial revision

  • 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 "cpu.h"
22#include "bsp.h"
23#include "shm.h"
24
25/*
26 *  Shm_Initialize_lock
27 *
28 *  Initialize the lock for the specified locked queue.
29 */
30
31void Shm_Initialize_lock(
32  Shm_Locked_queue_Control *lq_cb
33)
34{
35  lq_cb->lock = LQ_UNLOCKED;
36}
37
38/*  void _Shm_Lock( &lq_cb )
39 *
40 *  This shared memory locked queue support routine locks the
41 *  specified locked queue.  It disables interrupts to prevent
42 *  a deadlock condition.
43 */
44
45void Shm_Lock(
46  Shm_Locked_queue_Control *lq_cb
47)
48{
49  rtems_unsigned32 isr_level, oldlock;
50
51  rtems_interrupt_disable( isr_level );
52    Shm_isrstat = isr_level;
53    while ( 1 ) {
54      atomic_modify( SHM_LOCK_VALUE, &lq_cb->lock, oldlock );
55      if ( !(oldlock & SHM_LOCK_VALUE) )
56        return;
57      delay( 28 );        /* delay 28 microseconds */
58    }
59}
60
61/*
62 *  Shm_Unlock
63 *
64 *  Unlock the lock for the specified locked queue.
65 */
66
67void Shm_Unlock(
68  Shm_Locked_queue_Control *lq_cb
69)
70{
71  rtems_unsigned32 isr_level;
72
73  lq_cb->lock = SHM_UNLOCK_VALUE;
74  isr_level = Shm_isrstat;
75  rtems_interrupt_enable( isr_level );
76}
77
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