forked from Imagelibrary/rtems
85 lines
2.0 KiB
C
85 lines
2.0 KiB
C
/* Shared Memory Lock Routines
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*
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* This shared memory locked queue support routine need to be
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* able to lock the specified locked queue. Interrupts are
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* disabled while the queue is locked to prevent preemption
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* and deadlock when two tasks poll for the same lock.
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* previous level.
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*
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* COPYRIGHT (c) 1989-1999.
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* On-Line Applications Research Corporation (OAR).
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*
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* The license and distribution terms for this file may be
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* found in the file LICENSE in this distribution or at
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* http://www.rtems.org/license/LICENSE.
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*/
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#include <rtems.h>
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#include <bsp.h>
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#include <shm_driver.h>
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/*
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* Shm_Initialize_lock
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*
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* Initialize the lock for the specified locked queue.
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*/
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void Shm_Initialize_lock(
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Shm_Locked_queue_Control *lq_cb
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)
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{
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lq_cb->lock = LQ_UNLOCKED;
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}
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/* void _Shm_Lock( &lq_cb )
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*
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* This shared memory locked queue support routine locks the
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* specified locked queue. It disables interrupts to prevent
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* a deadlock condition.
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*/
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void Shm_Lock(
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Shm_Locked_queue_Control *lq_cb
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)
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{
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uint32_t isr_level;
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uint32_t *lockptr = (uint32_t*) &lq_cb->lock;
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uint32_t lock_value;
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lock_value = 0x80000000;
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rtems_interrupt_disable( isr_level );
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Shm_isrstat = isr_level;
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while ( lock_value ) {
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__asm__ volatile( ""
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: "=r" (lockptr), "=r" (lock_value)
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: "0" (lockptr), "1" (lock_value)
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);
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/*
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* If not available, then may want to delay to reduce load on lock.
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*
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* NOTE: BSP must initialize the counter facility. Delay value is BSP
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* dependent.
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*/
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if ( lock_value )
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rtems_counter_delay_nanoseconds( 100 );
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}
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}
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/*
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* Shm_Unlock
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*
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* Unlock the lock for the specified locked queue.
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*/
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void Shm_Unlock(
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Shm_Locked_queue_Control *lq_cb
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)
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{
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uint32_t isr_level;
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lq_cb->lock = SHM_UNLOCK_VALUE;
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isr_level = Shm_isrstat;
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rtems_interrupt_enable( isr_level );
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}
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