[uClinux-dev] [PATCH] coldfire context switch speedup

[Philippe De Muyter]

Hi Greg,

It is useless to preserve THREAD_SR in `resume'.  The real user's sr
is actually in the stack.  We also don't need to disable interrupts :
we'll never be in an invalid state, the sp switch is atomic.

Signed-off-by: Philippe De Muyter <phdm at macqel.be>

diff -r f8b279fd0eab arch/m68knommu/platform/5307/entry.S
--- a/arch/m68knommu/platform/5307/entry.S	Mon Mar 19 20:20:56 2007 -0700
+++ b/arch/m68knommu/platform/5307/entry.S	Thu Mar 22 13:43:39 2007 +0100
@@ -235,16 +235,12 @@ 2:
  * Beware - when entering resume, prev (the current task) is
  * in a0, next (the new task) is in a1,so don't change these
  * registers until their contents are no longer needed.
+ * This is always called in supervisor mode, so don't bother to save
+ * and restore sr; user's process sr is actually in the stack.
  */
 ENTRY(resume)
 	movel	%a0, %d1			/* get prev thread in d1 */
 
-	movew	%sr,%d0				/* save thread status reg */
-	movew	%d0,%a0@(TASK_THREAD+THREAD_SR)
-
-	oril	#0x700,%d0			/* disable interrupts */
-	move	%d0,%sr
-
 	movel	sw_usp,%d0			/* save usp */
 	movel	%d0,%a0@(TASK_THREAD+THREAD_USP)
 
@@ -255,7 +251,4 @@ ENTRY(resume)
 
 	movel	%a1@(TASK_THREAD+THREAD_USP),%a0 /* restore thread user stack */
 	movel	%a0, sw_usp
-
-	movew	%a1@(TASK_THREAD+THREAD_SR),%d0	/* restore thread status reg */
-	movew	%d0, %sr
 	rts