1 | /** |
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2 | * @file |
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3 | * |
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4 | * @brief Changes the Priority of a Thread |
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5 | * |
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6 | * @ingroup ScoreThread |
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7 | */ |
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8 | |
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9 | /* |
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10 | * COPYRIGHT (c) 1989-2011. |
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11 | * On-Line Applications Research Corporation (OAR). |
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12 | * |
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13 | * The license and distribution terms for this file may be |
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14 | * found in the file LICENSE in this distribution or at |
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15 | * http://www.rtems.com/license/LICENSE. |
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16 | */ |
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17 | |
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18 | #if HAVE_CONFIG_H |
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19 | #include "config.h" |
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20 | #endif |
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21 | |
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22 | #include <rtems/score/thread.h> |
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23 | #include <rtems/score/isr.h> |
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24 | #include <rtems/score/schedulerimpl.h> |
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25 | #include <rtems/score/threadq.h> |
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26 | |
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27 | void _Thread_Change_priority( |
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28 | Thread_Control *the_thread, |
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29 | Priority_Control new_priority, |
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30 | bool prepend_it |
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31 | ) |
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32 | { |
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33 | ISR_Level level; |
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34 | States_Control state, original_state; |
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35 | |
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36 | /* |
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37 | * Save original state |
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38 | */ |
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39 | original_state = the_thread->current_state; |
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40 | |
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41 | /* |
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42 | * Set a transient state for the thread so it is pulled off the Ready chains. |
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43 | * This will prevent it from being scheduled no matter what happens in an |
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44 | * ISR. |
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45 | */ |
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46 | _Thread_Set_transient( the_thread ); |
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47 | |
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48 | /* |
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49 | * Do not bother recomputing all the priority related information if |
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50 | * we are not REALLY changing priority. |
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51 | */ |
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52 | if ( the_thread->current_priority != new_priority ) |
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53 | _Thread_Set_priority( the_thread, new_priority ); |
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54 | |
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55 | _ISR_Disable( level ); |
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56 | |
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57 | /* |
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58 | * If the thread has more than STATES_TRANSIENT set, then it is blocked, |
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59 | * If it is blocked on a thread queue, then we need to requeue it. |
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60 | */ |
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61 | state = the_thread->current_state; |
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62 | if ( state != STATES_TRANSIENT ) { |
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63 | /* Only clear the transient state if it wasn't set already */ |
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64 | if ( ! _States_Is_transient( original_state ) ) |
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65 | the_thread->current_state = _States_Clear( STATES_TRANSIENT, state ); |
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66 | _ISR_Enable( level ); |
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67 | if ( _States_Is_waiting_on_thread_queue( state ) ) { |
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68 | _Thread_queue_Requeue( the_thread->Wait.queue, the_thread ); |
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69 | } |
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70 | return; |
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71 | } |
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72 | |
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73 | /* Only clear the transient state if it wasn't set already */ |
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74 | if ( ! _States_Is_transient( original_state ) ) { |
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75 | /* |
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76 | * Interrupts are STILL disabled. |
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77 | * We now know the thread will be in the READY state when we remove |
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78 | * the TRANSIENT state. So we have to place it on the appropriate |
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79 | * Ready Queue with interrupts off. |
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80 | */ |
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81 | the_thread->current_state = _States_Clear( STATES_TRANSIENT, state ); |
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82 | |
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83 | if ( prepend_it ) |
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84 | _Scheduler_Enqueue_first( the_thread ); |
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85 | else |
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86 | _Scheduler_Enqueue( the_thread ); |
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87 | } |
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88 | |
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89 | _ISR_Flash( level ); |
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90 | |
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91 | /* |
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92 | * We altered the set of thread priorities. So let's figure out |
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93 | * who is the heir and if we need to switch to them. |
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94 | */ |
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95 | _Scheduler_Schedule(); |
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96 | |
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97 | if ( !_Thread_Is_executing_also_the_heir() && |
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98 | _Thread_Executing->is_preemptible ) |
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99 | _Thread_Dispatch_necessary = true; |
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100 | _ISR_Enable( level ); |
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101 | } |
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