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2001-05-14 Till Straumann <strauman@slac.stanford.edu>

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* src/threaddispatch.c, src/threadhandler.c: Per PR211 fix
	saving/restoring floating point context.  The fpsave and fprestore
	routines are only used in a executing context which _is_ fp and hence
	has the FPU enabled. The current behavior required the FPU always to
	be on which is very dangerous if lazy context switching is used.
	[Joel Note: Some ports explicitly enabled the FPU in the FP save and
	restore routines to avoid this.]

	The patch also makes sure (on powerpc only) that the FPU is disabled
	for integer tasks. Note that this is crucial if deferred fp context
	switching is used. Otherwise, fp context corruption may go undetected!
	Also note that even tasks which merely push/pop FP registers to/from
	the stack without modifying them still MUST be FP tasks - otherwise
	(if lazy FP context switching is used), FP register corruption (of
	other, FP, tasks may occur)!

	Furthermore, (on PPC) by default, lazy FP context save/restore
	is _disabled_.
This commit is contained in:
Joel Sherrill
2002-05-14 17:45:36 +00:00
parent 06549dcf3f
commit 48f8968356
6 changed files with 94 additions and 22 deletions
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21
c/src/exec/score/ChangeLog
View File

@@ -1,3 +1,24 @@
2001-05-14 Till Straumann <strauman@slac.stanford.edu>
* src/threaddispatch.c, src/threadhandler.c: Per PR211 fix
saving/restoring floating point context. The fpsave and fprestore
routines are only used in a executing context which _is_ fp and hence
has the FPU enabled. The current behavior required the FPU always to
be on which is very dangerous if lazy context switching is used.
[Joel Note: Some ports explicitly enabled the FPU in the FP save and
restore routines to avoid this.]
The patch also makes sure (on powerpc only) that the FPU is disabled
for integer tasks. Note that this is crucial if deferred fp context
switching is used. Otherwise, fp context corruption may go undetected!
Also note that even tasks which merely push/pop FP registers to/from
the stack without modifying them still MUST be FP tasks - otherwise
(if lazy FP context switching is used), FP register corruption (of
other, FP, tasks may occur)!
Furthermore, (on PPC) by default, lazy FP context save/restore
is _disabled_.
2001-04-26 Joel Sherrill <joel@OARcorp.com>
* src/objectcomparenamestring.c: Fix typos.

26
c/src/exec/score/src/threaddispatch.c
View File

@@ -93,24 +93,28 @@ void _Thread_Dispatch( void )
*/
#if ( CPU_HARDWARE_FP == TRUE ) || ( CPU_SOFTWARE_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 ( CPU_USE_DEFERRED_FP_SWITCH != TRUE )
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 );
#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 );

11
c/src/exec/score/src/threadhandler.c
View File

@@ -78,6 +78,17 @@ void _Thread_Handler( void )
doneConstructors = 1;
#endif
#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 );
_Thread_Allocated_fp = executing;
}
#endif
#endif
/*
* Take care that 'begin' extensions get to complete before
* 'switch' extensions can run. This means must keep dispatch