From 5c3d2509593476869e791111cd3d93cc1e840b3a Mon Sep 17 00:00:00 2001 From: Sebastian Huber Date: Fri, 4 Jul 2014 14:34:23 +0200 Subject: score: Implement scheduler helping protocol The following scheduler operations return a thread in need for help - unblock, - change priority, and - yield. A thread in need for help is a thread that encounters a scheduler state change from scheduled to ready or a thread that cannot be scheduled in an unblock operation. Such a thread can ask threads which depend on resources owned by this thread for help. Add a new ask for help scheduler operation. This operation is used by _Scheduler_Ask_for_help() to help threads in need for help returned by the operations mentioned above. This operation is also used by _Scheduler_Thread_change_resource_root() in case the root of a resource sub-tree changes. A use case is the ownership change of a resource. In case it is not possible to schedule a thread in need for help, then the corresponding scheduler node will be placed into the set of ready scheduler nodes of the scheduler instance. Once a state change from ready to scheduled happens for this scheduler node it may be used to schedule the thread in need for help. --- cpukit/score/include/rtems/score/scheduler.h | 47 ++++++++++++++++++++++++++++ 1 file changed, 47 insertions(+) (limited to 'cpukit/score/include/rtems/score/scheduler.h') diff --git a/cpukit/score/include/rtems/score/scheduler.h b/cpukit/score/include/rtems/score/scheduler.h index 993ae55b29..8da988fffd 100644 --- a/cpukit/score/include/rtems/score/scheduler.h +++ b/cpukit/score/include/rtems/score/scheduler.h @@ -90,6 +90,31 @@ typedef struct { bool ); +#if defined(RTEMS_SMP) + /** + * Ask for help operation. + * + * @param[in] scheduler The scheduler of the thread offering help. + * @param[in] offers_help The thread offering help. + * @param[in] needs_help The thread needing help. + * + * @retval needs_help It was not possible to schedule the thread needing + * help, so it is returned to continue the search for help. + * @retval next_needs_help It was possible to schedule the thread needing + * help, but this displaced another thread eligible to ask for help. So + * this thread is returned to start a new search for help. + * @retval NULL It was possible to schedule the thread needing help, and no + * other thread needs help as a result. + * + * @see _Scheduler_Ask_for_help(). + */ + Thread_Control *( *ask_for_help )( + const Scheduler_Control *scheduler, + Thread_Control *offers_help, + Thread_Control *needs_help + ); +#endif + /** @see _Scheduler_Node_initialize() */ void ( *node_initialize )( const Scheduler_Control *, Thread_Control * ); @@ -375,6 +400,28 @@ extern const Scheduler_Control _Scheduler_Table[]; extern const Scheduler_Assignment _Scheduler_Assignments[]; #endif +#if defined(RTEMS_SMP) + /** + * @brief Does nothing. + * + * @param[in] scheduler Unused. + * @param[in] offers_help Unused. + * @param[in] needs_help Unused. + * + * @retval NULL Always. + */ + Thread_Control *_Scheduler_default_Ask_for_help( + const Scheduler_Control *scheduler, + Thread_Control *offers_help, + Thread_Control *needs_help + ); + + #define SCHEDULER_OPERATION_DEFAULT_ASK_FOR_HELP \ + _Scheduler_default_Ask_for_help, +#else + #define SCHEDULER_OPERATION_DEFAULT_ASK_FOR_HELP +#endif + /** * @brief Does nothing. * -- cgit v1.2.3