source: rtems/c/src/lib/libbsp/i960/rxgen960/shmsupp/lock.c @ 48bfd992

4.104.114.84.95
Last change on this file since 48bfd992 was 48bfd992, checked in by Joel Sherrill <joel.sherrill@…>, on Nov 30, 1999 at 7:58:02 PM

Renamed shm.h to shm_driver.h to avoid conflicts with POSIX shm.h.

Renamed file shmsupp/intr.c in some BSPs to shmsupp/cause_intr.c to
avoid conflict with rtems/src/intr.c (Classic API Interrupt Manager).

  • Property mode set to 100644
File size: 1.6 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) 1989-1997.
10 *  On-Line Applications Research Corporation (OAR).
11 *  Copyright assigned to U.S. Government, 1994.
12 *
13 *  The license and distribution terms for this file may in
14 *  the file LICENSE in this distribution or at
15 *  http://www.OARcorp.com/rtems/license.html.
16 *
17 *  $Id$
18 */
19
20#include <rtems.h>
21#include <bsp.h>
22#include <shm_driver.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, oldlock;
49
50  rtems_interrupt_disable( isr_level );
51    Shm_isrstat = isr_level;
52    while ( 1 ) {
53      atomic_modify( SHM_LOCK_VALUE, &lq_cb->lock, oldlock );
54      if ( !(oldlock & SHM_LOCK_VALUE) )
55        return;
56      delay( 28 );        /* delay 28 microseconds */
57    }
58}
59
60/*
61 *  Shm_Unlock
62 *
63 *  Unlock the lock for the specified locked queue.
64 */
65
66void Shm_Unlock(
67  Shm_Locked_queue_Control *lq_cb
68)
69{
70  rtems_unsigned32 isr_level;
71
72  lq_cb->lock = SHM_UNLOCK_VALUE;
73  isr_level = Shm_isrstat;
74  rtems_interrupt_enable( isr_level );
75}
76
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