1 | /* SPDX-License-Identifier: BSD-2-Clause */ |
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2 | |
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3 | /* Shared Memory Lock Routines |
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4 | * |
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5 | * This shared memory locked queue support routine need to be |
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6 | * able to lock the specified locked queue. Interrupts are |
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7 | * disabled while the queue is locked to prevent preemption |
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8 | * and deadlock when two tasks poll for the same lock. |
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9 | * previous level. |
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10 | * |
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11 | * COPYRIGHT (c) 1989-1999. |
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12 | * On-Line Applications Research Corporation (OAR). |
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13 | * |
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14 | * Redistribution and use in source and binary forms, with or without |
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15 | * modification, are permitted provided that the following conditions |
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16 | * are met: |
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17 | * 1. Redistributions of source code must retain the above copyright |
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18 | * notice, this list of conditions and the following disclaimer. |
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19 | * 2. Redistributions in binary form must reproduce the above copyright |
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20 | * notice, this list of conditions and the following disclaimer in the |
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21 | * documentation and/or other materials provided with the distribution. |
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22 | * |
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23 | * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" |
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24 | * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
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25 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
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26 | * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE |
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27 | * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |
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28 | * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF |
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29 | * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
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30 | * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN |
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31 | * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) |
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32 | * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
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33 | * POSSIBILITY OF SUCH DAMAGE. |
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34 | */ |
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35 | |
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36 | #include <rtems.h> |
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37 | #include <bsp.h> |
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38 | #include <shm_driver.h> |
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39 | |
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40 | /* |
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41 | * Shm_Initialize_lock |
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42 | * |
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43 | * Initialize the lock for the specified locked queue. |
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44 | */ |
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45 | |
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46 | void Shm_Initialize_lock( |
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47 | Shm_Locked_queue_Control *lq_cb |
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48 | ) |
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49 | { |
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50 | lq_cb->lock = LQ_UNLOCKED; |
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51 | } |
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52 | |
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53 | /* void _Shm_Lock( &lq_cb ) |
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54 | * |
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55 | * This shared memory locked queue support routine locks the |
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56 | * specified locked queue. It disables interrupts to prevent |
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57 | * a deadlock condition. |
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58 | */ |
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59 | |
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60 | void Shm_Lock( |
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61 | Shm_Locked_queue_Control *lq_cb |
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62 | ) |
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63 | { |
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64 | uint32_t isr_level; |
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65 | uint32_t *lockptr = (uint32_t*) &lq_cb->lock; |
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66 | uint32_t lock_value; |
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67 | |
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68 | lock_value = 0x80000000; |
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69 | rtems_interrupt_disable( isr_level ); |
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70 | |
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71 | Shm_isrstat = isr_level; |
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72 | while ( lock_value ) { |
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73 | __asm__ volatile( "" |
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74 | : "=r" (lockptr), "=r" (lock_value) |
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75 | : "0" (lockptr), "1" (lock_value) |
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76 | ); |
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77 | /* |
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78 | * If not available, then may want to delay to reduce load on lock. |
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79 | * |
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80 | * NOTE: BSP must initialize the counter facility. Delay value is BSP |
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81 | * dependent. |
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82 | */ |
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83 | if ( lock_value ) |
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84 | rtems_counter_delay_nanoseconds( 100 ); |
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85 | } |
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86 | } |
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87 | |
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88 | /* |
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89 | * Shm_Unlock |
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90 | * |
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91 | * Unlock the lock for the specified locked queue. |
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92 | */ |
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93 | |
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94 | void Shm_Unlock( |
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95 | Shm_Locked_queue_Control *lq_cb |
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96 | ) |
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97 | { |
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98 | uint32_t isr_level; |
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99 | |
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100 | lq_cb->lock = SHM_UNLOCK_VALUE; |
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101 | isr_level = Shm_isrstat; |
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102 | rtems_interrupt_enable( isr_level ); |
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103 | } |
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