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/*
* Thread Handler
*
* COPYRIGHT (c) 1989-2009.
* On-Line Applications Research Corporation (OAR).
*
* The license and distribution terms for this file may be
* found in the file LICENSE in this distribution or at
* http://www.rtems.com/license/LICENSE.
*
* $Id$
*/
#if HAVE_CONFIG_H
#include "config.h"
#endif
#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>
#ifndef __RTEMS_USE_TICKS_FOR_STATISTICS__
#include <rtems/score/timestamp.h>
#endif
#if defined(RTEMS_SMP)
#include <rtems/score/smp.h>
#endif
/**
* _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();
*
* INTERRUPT LATENCY:
* dispatch thread
* no dispatch thread
*/
void _Thread_Dispatch( void )
{
Thread_Control *executing;
Thread_Control *heir;
ISR_Level level;
_Thread_Disable_dispatch();
#if defined(RTEMS_SMP)
/*
* If necessary, send dispatch request to other cores.
*/
_SMP_Request_other_cores_to_dispatch();
#endif
/*
* Now determine if we need to perform a dispatch on the current CPU.
*/
executing = _Thread_Executing;
_ISR_Disable( level );
while ( _Thread_Dispatch_necessary == true ) {
heir = _Thread_Heir;
_Thread_Dispatch_necessary = false;
_Thread_Executing = heir;
/*
* When the heir and executing are the same, then we are being
* requested to do the post switch dispatching. This is normally
* done to dispatch signals.
*/
if ( heir == executing )
goto post_switch;
/*
* Since heir and executing are not the same, we need to do a real
* context switch.
*/
#if __RTEMS_ADA__
executing->rtems_ada_self = rtems_ada_self;
rtems_ada_self = heir->rtems_ada_self;
#endif
if ( heir->budget_algorithm == THREAD_CPU_BUDGET_ALGORITHM_RESET_TIMESLICE )
heir->cpu_time_budget = _Thread_Ticks_per_timeslice;
_ISR_Enable( level );
#ifndef __RTEMS_USE_TICKS_FOR_STATISTICS__
{
Timestamp_Control uptime, ran;
_TOD_Get_uptime( &uptime );
_Timestamp_Subtract(
&_Thread_Time_of_last_context_switch,
&uptime,
&ran
);
_Timestamp_Add_to( &executing->cpu_time_used, &ran );
_Thread_Time_of_last_context_switch = uptime;
}
#else
{
TOD_Get_uptime( &_Thread_Time_of_last_context_switch );
heir->cpu_time_used++;
}
#endif
/*
* Switch libc's task specific data.
*/
if ( _Thread_libc_reent ) {
executing->libc_reent = *_Thread_libc_reent;
*_Thread_libc_reent = heir->libc_reent;
}
_User_extensions_Thread_switch( executing, heir );
/*
* 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 ) || ( CPU_SOFTWARE_FP == TRUE )
#if ( CPU_USE_DEFERRED_FP_SWITCH != TRUE )
if ( executing->fp_context != NULL )
_Context_Save_fp( &executing->fp_context );
#endif
#endif
_Context_Switch( &executing->Registers, &heir->Registers );
#if ( CPU_HARDWARE_FP == TRUE ) || ( CPU_SOFTWARE_FP == TRUE )
#if ( CPU_USE_DEFERRED_FP_SWITCH == TRUE )
if ( (executing->fp_context != NULL) &&
!_Thread_Is_allocated_fp( executing ) ) {
if ( _Thread_Allocated_fp != NULL )
_Context_Save_fp( &_Thread_Allocated_fp->fp_context );
_Context_Restore_fp( &executing->fp_context );
_Thread_Allocated_fp = executing;
}
#else
if ( executing->fp_context != NULL )
_Context_Restore_fp( &executing->fp_context );
#endif
#endif
executing = _Thread_Executing;
_ISR_Disable( level );
}
post_switch:
_ISR_Enable( level );
_Thread_Unnest_dispatch();
_API_extensions_Run_postswitch();
}
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