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/*
* Thread Handler
*
*
* COPYRIGHT (c) 1989-1999.
* On-Line Applications Research Corporation (OAR).
*
* 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();
}
}
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