1 | /* |
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2 | * COPYRIGHT (c) 1989-2009. |
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3 | * On-Line Applications Research Corporation (OAR). |
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4 | * |
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5 | * The license and distribution terms for this file may be |
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6 | * found in the file LICENSE in this distribution or at |
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7 | * http://www.rtems.com/license/LICENSE. |
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8 | */ |
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9 | |
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10 | #if HAVE_CONFIG_H |
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11 | #include "config.h" |
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12 | #endif |
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13 | |
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14 | #include <rtems/system.h> |
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15 | #include <rtems/score/schedulerpriority.h> |
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16 | |
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17 | void _Scheduler_priority_Tick( void ) |
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18 | { |
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19 | Thread_Control *executing; |
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20 | |
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21 | executing = _Thread_Executing; |
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22 | |
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23 | #ifdef __RTEMS_USE_TICKS_FOR_STATISTICS__ |
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24 | /* |
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25 | * Increment the number of ticks this thread has been executing |
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26 | */ |
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27 | executing->cpu_time_used++; |
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28 | #endif |
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29 | |
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30 | /* |
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31 | * If the thread is not preemptible or is not ready, then |
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32 | * just return. |
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33 | */ |
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34 | |
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35 | if ( !executing->is_preemptible ) |
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36 | return; |
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37 | |
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38 | if ( !_States_Is_ready( executing->current_state ) ) |
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39 | return; |
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40 | |
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41 | /* |
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42 | * The cpu budget algorithm determines what happens next. |
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43 | */ |
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44 | |
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45 | switch ( executing->budget_algorithm ) { |
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46 | case THREAD_CPU_BUDGET_ALGORITHM_NONE: |
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47 | break; |
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48 | |
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49 | case THREAD_CPU_BUDGET_ALGORITHM_RESET_TIMESLICE: |
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50 | #if defined(RTEMS_SCORE_THREAD_ENABLE_EXHAUST_TIMESLICE) |
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51 | case THREAD_CPU_BUDGET_ALGORITHM_EXHAUST_TIMESLICE: |
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52 | #endif |
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53 | if ( (int)(--executing->cpu_time_budget) <= 0 ) { |
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54 | |
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55 | /* |
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56 | * A yield performs the ready chain mechanics needed when |
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57 | * resetting a timeslice. If no other thread's are ready |
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58 | * at the priority of the currently executing thread, then the |
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59 | * executing thread's timeslice is reset. Otherwise, the |
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60 | * currently executing thread is placed at the rear of the |
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61 | * FIFO for this priority and a new heir is selected. |
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62 | */ |
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63 | _Scheduler_Yield(); |
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64 | executing->cpu_time_budget = _Thread_Ticks_per_timeslice; |
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65 | } |
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66 | break; |
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67 | |
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68 | #if defined(RTEMS_SCORE_THREAD_ENABLE_SCHEDULER_CALLOUT) |
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69 | case THREAD_CPU_BUDGET_ALGORITHM_CALLOUT: |
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70 | if ( --executing->cpu_time_budget == 0 ) |
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71 | (*executing->budget_callout)( executing ); |
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72 | break; |
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73 | #endif |
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74 | } |
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75 | } |
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