From 701dd96f598bd58a41884795ba5bf0b5da337d78 Mon Sep 17 00:00:00 2001 From: Sebastian Huber Date: Thu, 12 Jun 2014 14:37:57 +0200 Subject: score: PR2181: Add _Thread_Yield() The _Scheduler_Yield() was called by the executing thread with thread dispatching disabled and interrupts enabled. The rtems_task_suspend() is explicitly allowed in ISRs: http://rtems.org/onlinedocs/doc-current/share/rtems/html/c_user/Interrupt-Manager-Directives-Allowed-from-an-ISR.html#Interrupt-Manager-Directives-Allowed-from-an-ISR Unlike the other scheduler operations the locking was performed inside the operation. This lead to the following race condition. Suppose a ISR suspends the executing thread right before the yield scheduler operation. Now the executing thread is not longer in the set of ready threads. The typical scheduler operations did not check the thread state and will now extract the thread again and enqueue it. This corrupted data structures. Add _Thread_Yield() and do the scheduler yield operation with interrupts disabled. This has a negligible effect on the interrupt latency. --- cpukit/score/src/schedulerpriorityyield.c | 23 +++++++++-------------- 1 file changed, 9 insertions(+), 14 deletions(-) (limited to 'cpukit/score/src/schedulerpriorityyield.c') diff --git a/cpukit/score/src/schedulerpriorityyield.c b/cpukit/score/src/schedulerpriorityyield.c index f2aeada660..60bab3983e 100644 --- a/cpukit/score/src/schedulerpriorityyield.c +++ b/cpukit/score/src/schedulerpriorityyield.c @@ -19,7 +19,6 @@ #endif #include -#include #include void _Scheduler_priority_Yield( @@ -29,23 +28,19 @@ void _Scheduler_priority_Yield( { Scheduler_priority_Node *node = _Scheduler_priority_Node_get( the_thread ); Chain_Control *ready_chain = node->Ready_queue.ready_chain; - ISR_Level level; (void) scheduler; - _ISR_Disable( level ); - if ( !_Chain_Has_only_one_node( ready_chain ) ) { - _Chain_Extract_unprotected( &the_thread->Object.Node ); - _Chain_Append_unprotected( ready_chain, &the_thread->Object.Node ); + if ( !_Chain_Has_only_one_node( ready_chain ) ) { + _Chain_Extract_unprotected( &the_thread->Object.Node ); + _Chain_Append_unprotected( ready_chain, &the_thread->Object.Node ); - _ISR_Flash( level ); - - if ( _Thread_Is_heir( the_thread ) ) - _Thread_Heir = (Thread_Control *) _Chain_First( ready_chain ); - _Thread_Dispatch_necessary = true; + if ( _Thread_Is_heir( the_thread ) ) { + _Thread_Heir = (Thread_Control *) _Chain_First( ready_chain ); } - else if ( !_Thread_Is_heir( the_thread ) ) - _Thread_Dispatch_necessary = true; - _ISR_Enable( level ); + _Thread_Dispatch_necessary = true; + } else if ( !_Thread_Is_heir( the_thread ) ) { + _Thread_Dispatch_necessary = true; + } } -- cgit v1.2.3