[PATCH] PPC/PPC64: Fix FP state corruption on UP

[Paul Mackerras]

Unfortunately the patch Ben sent last week to fix a bug in the saving
and restoring of floating-point and altivec context across signal
handlers introduced another bug, which tends to corrupt the FP and
altivec contexts of other tasks.  This patch fixes the problem for
both ppc32 and ppc64.  Please apply.

Signed-off-by: Paul Mackerras <paulus@xxxxxxxxx>

diff -urN linux-2.5/arch/ppc/kernel/signal.c test/arch/ppc/kernel/signal.c
--- linux-2.5/arch/ppc/kernel/signal.c	2004-10-20 08:16:36.000000000 +1000
+++ test/arch/ppc/kernel/signal.c	2004-10-27 14:29:48.494955208 +1000
@@ -290,7 +290,7 @@
 
 	/* force the process to reload the FP registers from
 	   current->thread when it next does FP instructions */
-	regs->msr &= ~MSR_FP;
+	regs->msr &= ~(MSR_FP | MSR_FE0 | MSR_FE1);
 	if (__copy_from_user(current->thread.fpr, &sr->mc_fregs,
 			     sizeof(sr->mc_fregs)))
 		return 1;
@@ -330,9 +330,14 @@
 #endif /* CONFIG_SPE */
 
 #ifndef CONFIG_SMP
-	last_task_used_math = NULL;
-	last_task_used_altivec = NULL;
-	last_task_used_spe = NULL;
+	preempt_disable();
+	if (last_task_used_math == current)
+		last_task_used_math = NULL;
+	if (last_task_used_altivec == current)
+		last_task_used_altivec = NULL;
+	if (last_task_used_spe == current)
+		last_task_used_spe = NULL;
+	preempt_enable();
 #endif
 	return 0;
 }
diff -urN linux-2.5/arch/ppc64/kernel/signal.c test/arch/ppc64/kernel/signal.c
--- linux-2.5/arch/ppc64/kernel/signal.c	2004-10-20 08:16:36.000000000 +1000
+++ test/arch/ppc64/kernel/signal.c	2004-10-27 14:31:57.301942136 +1000
@@ -224,8 +224,12 @@
 #endif /* CONFIG_ALTIVEC */
 
 #ifndef CONFIG_SMP
-	last_task_used_math = NULL;
-	last_task_used_altivec = NULL;
+	preempt_disable();
+	if (last_task_used_math == current)
+		last_task_used_math = NULL;
+	if (last_task_used_altivec == current)
+		last_task_used_altivec = NULL;
+	preempt_enable();
 #endif
 	/* Force reload of FP/VEC */
 	regs->msr &= ~(MSR_FP | MSR_FE0 | MSR_FE1 | MSR_VEC);
diff -urN linux-2.5/arch/ppc64/kernel/signal32.c test/arch/ppc64/kernel/signal32.c
--- linux-2.5/arch/ppc64/kernel/signal32.c	2004-10-20 08:16:36.000000000 +1000
+++ test/arch/ppc64/kernel/signal32.c	2004-10-27 14:32:45.086999136 +1000
@@ -235,8 +235,12 @@
 #endif /* CONFIG_ALTIVEC */
 
 #ifndef CONFIG_SMP
-	last_task_used_math = NULL;
-	last_task_used_altivec = NULL;
+	preempt_disable();
+	if (last_task_used_math == current)
+		last_task_used_math = NULL;
+	if (last_task_used_altivec == current)
+		last_task_used_altivec = NULL;
+	preempt_enable();
 #endif
 	return 0;
 }
-
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