[afe99c2] | 1 | /* Shared Memory Lock Routines |
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| 2 | * |
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| 3 | * This shared memory locked queue support routine need to be |
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| 4 | * able to lock the specified locked queue. Interrupts are |
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| 5 | * disabled while the queue is locked to prevent preemption |
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| 6 | * and deadlock when two tasks poll for the same lock. |
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| 7 | * previous level. |
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| 8 | * |
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[08311cc3] | 9 | * COPYRIGHT (c) 1989-1999. |
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[afe99c2] | 10 | * On-Line Applications Research Corporation (OAR). |
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| 11 | * |
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[98e4ebf5] | 12 | * The license and distribution terms for this file may be |
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| 13 | * found in the file LICENSE in this distribution or at |
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[03f2154e] | 14 | * http://www.OARcorp.com/rtems/license.html. |
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[afe99c2] | 15 | * |
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| 16 | * $Id$ |
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| 17 | */ |
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| 18 | |
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| 19 | #include <rtems.h> |
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| 20 | #include <bsp.h> |
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[48bfd992] | 21 | #include <shm_driver.h> |
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[afe99c2] | 22 | |
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| 23 | /* |
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| 24 | * Shm_Initialize_lock |
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| 25 | * |
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| 26 | * Initialize the lock for the specified locked queue. |
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| 27 | */ |
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| 28 | |
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| 29 | void Shm_Initialize_lock( |
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| 30 | Shm_Locked_queue_Control *lq_cb |
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| 31 | ) |
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| 32 | { |
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| 33 | lq_cb->lock = LQ_UNLOCKED; |
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| 34 | } |
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| 35 | |
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| 36 | /* void _Shm_Lock( &lq_cb ) |
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| 37 | * |
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| 38 | * This shared memory locked queue support routine locks the |
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| 39 | * specified locked queue. It disables interrupts to prevent |
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| 40 | * a deadlock condition. |
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| 41 | */ |
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| 42 | |
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| 43 | void Shm_Lock( |
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| 44 | Shm_Locked_queue_Control *lq_cb |
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| 45 | ) |
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| 46 | { |
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| 47 | rtems_unsigned32 isr_level; |
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| 48 | rtems_unsigned32 *lockptr = (rtems_unsigned32 *)&lq_cb->lock; |
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| 49 | |
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| 50 | rtems_interrupt_disable( isr_level ); |
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| 51 | Shm_isrstat = isr_level; |
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| 52 | asm volatile( "lockit:" : : ); |
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| 53 | asm volatile( "tas %0@" : "=a" (lockptr) : "0" (lockptr) ); |
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| 54 | asm volatile( "bne lockit" : : ); |
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| 55 | /* should delay */ |
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| 56 | } |
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| 57 | |
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| 58 | /* |
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| 59 | * Shm_Unlock |
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| 60 | * |
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| 61 | * Unlock the lock for the specified locked queue. |
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| 62 | */ |
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| 63 | |
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| 64 | void Shm_Unlock( |
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| 65 | Shm_Locked_queue_Control *lq_cb |
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| 66 | ) |
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| 67 | { |
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| 68 | rtems_unsigned32 isr_level; |
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| 69 | |
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| 70 | lq_cb->lock = SHM_UNLOCK_VALUE; |
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| 71 | isr_level = Shm_isrstat; |
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| 72 | rtems_interrupt_enable( isr_level ); |
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| 73 | } |
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| 74 | |
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