source: rtems/c/src/lib/libbsp/no_cpu/no_bsp/shmsupp/lock.c @ b547e84

Last change on this file since b547e84 was b547e84, checked in by Joel Sherrill <joel.sherrill@…>, on Sep 4, 2003 at 6:44:56 PM

2003-09-04 Joel Sherrill <joel@…>

  • clock/ckinit.c, console/console.c, include/bsp.h, shmsupp/addrconv.c, shmsupp/getcfg.c, shmsupp/lock.c, shmsupp/mpisr.c, startup/bspclean.c, startup/bspstart.c, startup/linkcmds, startup/main.c, startup/setvec.c, timer/timer.c, timer/timerisr.c: URL for license changed.
  • Property mode set to 100644
File size: 1.9 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) 1989-1999.
10 *  On-Line Applications Research Corporation (OAR).
11 *
12 *  The license and distribution terms for this file may be
13 *  found in the file LICENSE in this distribution or at
14 *  http://www.rtems.com/license/LICENSE.
15 *
16 *  $Id$
17 */
18
19#include <rtems.h>
20#include <bsp.h>
21#include <shm_driver.h>
22
23/*
24 *  Shm_Initialize_lock
25 *
26 *  Initialize the lock for the specified locked queue.
27 */
28
29void Shm_Initialize_lock(
30  Shm_Locked_queue_Control *lq_cb
31)
32{
33  lq_cb->lock = LQ_UNLOCKED;
34}
35
36/*  void _Shm_Lock( &lq_cb )
37 *
38 *  This shared memory locked queue support routine locks the
39 *  specified locked queue.  It disables interrupts to prevent
40 *  a deadlock condition.
41 */
42
43void Shm_Lock(
44  Shm_Locked_queue_Control *lq_cb
45)
46{
47  rtems_unsigned32 isr_level;
48  rtems_unsigned32 *lockptr = (rtems_unsigned32 *) &lq_cb->lock;
49  rtems_unsigned32 lock_value;
50
51  lock_value = 0x80000000;
52  rtems_interrupt_disable( isr_level );
53
54    Shm_isrstat = isr_level;
55    while ( lock_value ) {
56      asm volatile( ""
57                         : "=r" (lockptr), "=r" (lock_value)
58                         : "0" (lockptr),  "1" (lock_value)
59                  );
60      /*
61       *  If not available, then may want to delay to reduce load on lock.
62       */
63
64      if ( lock_value )
65        rtems_bsp_delay( 10 );   /* approximately 10 microseconds */
66   }
67}
68
69/*
70 *  Shm_Unlock
71 *
72 *  Unlock the lock for the specified locked queue.
73 */
74
75void Shm_Unlock(
76  Shm_Locked_queue_Control *lq_cb
77)
78{
79  rtems_unsigned32 isr_level;
80
81  lq_cb->lock = SHM_UNLOCK_VALUE;
82  isr_level = Shm_isrstat;
83  rtems_interrupt_enable( isr_level );
84}
85
Note: See TracBrowser for help on using the repository browser.