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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9 | * COPYRIGHT (c) 1989, 1990, 1991, 1992, 1993, 1994. |
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10 | * On-Line Applications Research Corporation (OAR). |
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11 | * All rights assigned to U.S. Government, 1994. |
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12 | * |
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13 | * This material may be reproduced by or for the U.S. Government pursuant |
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14 | * to the copyright license under the clause at DFARS 252.227-7013. This |
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15 | * notice must appear in all copies of this file and its derivatives. |
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16 | * |
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17 | * $Id$ |
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18 | */ |
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19 | |
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20 | #include <rtems.h> |
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21 | #include <bsp.h> |
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22 | #include <shm.h> |
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23 | |
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24 | /* |
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25 | * Shm_Initialize_lock |
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26 | * |
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27 | * Initialize the lock for the specified locked queue. |
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28 | */ |
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29 | |
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30 | void Shm_Initialize_lock( |
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31 | Shm_Locked_queue_Control *lq_cb |
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32 | ) |
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33 | { |
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34 | lq_cb->lock = LQ_UNLOCKED; |
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35 | } |
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36 | |
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37 | /* void _Shm_Lock( &lq_cb ) |
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38 | * |
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39 | * This shared memory locked queue support routine locks the |
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40 | * specified locked queue. It disables interrupts to prevent |
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41 | * a deadlock condition. |
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42 | */ |
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43 | |
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44 | void Shm_Lock( |
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45 | Shm_Locked_queue_Control *lq_cb |
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46 | ) |
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47 | { |
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48 | rtems_unsigned32 isr_level, oldlock; |
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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 | while ( 1 ) { |
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53 | atomic_modify( SHM_LOCK_VALUE, &lq_cb->lock, oldlock ); |
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54 | if ( !(oldlock & SHM_LOCK_VALUE) ) |
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55 | return; |
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56 | delay( 28 ); /* delay 28 microseconds */ |
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57 | } |
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58 | } |
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59 | |
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60 | /* |
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61 | * Shm_Unlock |
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62 | * |
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63 | * Unlock the lock for the specified locked queue. |
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64 | */ |
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65 | |
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66 | void Shm_Unlock( |
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67 | Shm_Locked_queue_Control *lq_cb |
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68 | ) |
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69 | { |
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70 | rtems_unsigned32 isr_level; |
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71 | |
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72 | lq_cb->lock = SHM_UNLOCK_VALUE; |
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73 | isr_level = Shm_isrstat; |
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74 | rtems_interrupt_enable( isr_level ); |
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75 | } |
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76 | |
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