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Diffstat (limited to '')
-rw-r--r-- | cpukit/score/src/threaddispatch.c | 130 |
1 files changed, 130 insertions, 0 deletions
diff --git a/cpukit/score/src/threaddispatch.c b/cpukit/score/src/threaddispatch.c new file mode 100644 index 0000000000..8c391d0d58 --- /dev/null +++ b/cpukit/score/src/threaddispatch.c @@ -0,0 +1,130 @@ +/* + * Thread Handler + * + * + * COPYRIGHT (c) 1989-1998. + * On-Line Applications Research Corporation (OAR). + * Copyright assigned to U.S. Government, 1994. + * + * The license and distribution terms for this file may be + * found in found in the file LICENSE in this distribution or at + * http://www.OARcorp.com/rtems/license.html. + * + * $Id$ + */ + +#include <rtems/system.h> +#include <rtems/score/apiext.h> +#include <rtems/score/context.h> +#include <rtems/score/interr.h> +#include <rtems/score/isr.h> +#include <rtems/score/object.h> +#include <rtems/score/priority.h> +#include <rtems/score/states.h> +#include <rtems/score/sysstate.h> +#include <rtems/score/thread.h> +#include <rtems/score/threadq.h> +#include <rtems/score/userext.h> +#include <rtems/score/wkspace.h> + +/*PAGE + * + * _Thread_Dispatch + * + * This kernel routine determines if a dispatch is needed, and if so + * dispatches to the heir thread. Once the heir is running an attempt + * is made to dispatch any ASRs. + * + * ALTERNATE ENTRY POINTS: + * void _Thread_Enable_dispatch(); + * + * Input parameters: NONE + * + * Output parameters: NONE + * + * INTERRUPT LATENCY: + * dispatch thread + * no dispatch thread + */ + +#if ( CPU_INLINE_ENABLE_DISPATCH == FALSE ) +void _Thread_Enable_dispatch( void ) +{ + if ( --_Thread_Dispatch_disable_level ) + return; + _Thread_Dispatch(); +} +#endif + +void _Thread_Dispatch( void ) +{ + Thread_Control *executing; + Thread_Control *heir; + ISR_Level level; + + executing = _Thread_Executing; + _ISR_Disable( level ); + while ( _Context_Switch_necessary == TRUE ) { + heir = _Thread_Heir; + _Thread_Dispatch_disable_level = 1; + _Context_Switch_necessary = FALSE; + _Thread_Executing = heir; + executing->rtems_ada_self = rtems_ada_self; + rtems_ada_self = heir->rtems_ada_self; + _ISR_Enable( level ); + + heir->ticks_executed++; + + _User_extensions_Thread_switch( executing, heir ); + + if ( heir->budget_algorithm == THREAD_CPU_BUDGET_ALGORITHM_RESET_TIMESLICE ) + heir->cpu_time_budget = _Thread_Ticks_per_timeslice; + + /* + * If the CPU has hardware floating point, then we must address saving + * and restoring it as part of the context switch. + * + * The second conditional compilation section selects the algorithm used + * to context switch between floating point tasks. The deferred algorithm + * can be significantly better in a system with few floating point tasks + * because it reduces the total number of save and restore FP context + * operations. However, this algorithm can not be used on all CPUs due + * to unpredictable use of FP registers by some compilers for integer + * operations. + */ + +#if ( CPU_HARDWARE_FP == TRUE ) +#if ( CPU_USE_DEFERRED_FP_SWITCH == TRUE ) + if ( (heir->fp_context != NULL) && !_Thread_Is_allocated_fp( heir ) ) { + if ( _Thread_Allocated_fp != NULL ) + _Context_Save_fp( &_Thread_Allocated_fp->fp_context ); + _Context_Restore_fp( &heir->fp_context ); + _Thread_Allocated_fp = heir; + } +#else + if ( executing->fp_context != NULL ) + _Context_Save_fp( &executing->fp_context ); + + if ( heir->fp_context != NULL ) + _Context_Restore_fp( &heir->fp_context ); +#endif +#endif + + _Context_Switch( &executing->Registers, &heir->Registers ); + + executing = _Thread_Executing; + + _ISR_Disable( level ); + } + + _Thread_Dispatch_disable_level = 0; + + _ISR_Enable( level ); + + if ( _Thread_Do_post_task_switch_extension || + executing->do_post_task_switch_extension ) { + executing->do_post_task_switch_extension = FALSE; + _API_extensions_Run_postswitch(); + } + +} |