[PATCH] ppc64: fix hang on oprofile shutdown

We had a problem in our dummy perfmon handler where we wouldnt reset the
PMAO bit.  If the bit ended up set and oprofile shutdown and removed its
handler then we would end up in a hard loop taking perfmon exceptions.
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/ppc64/kernel/traps.c

@@ -522,12 +522,13 @@ void AltivecUnavailableException(struct pt_regs *regs)
 
 /* Ensure exceptions are disabled */
 #define MMCR0_PMXE      (1UL << (31 - 5))
+#define MMCR0_PMAO      (1UL << (31 - 24))
 
 static void dummy_perf(struct pt_regs *regs)
 {
 	unsigned int mmcr0 = mfspr(SPRN_MMCR0);
 
-	mmcr0 &= ~MMCR0_PMXE;
+	mmcr0 &= ~(MMCR0_PMXE|MMCR0_PMAO);
 	mtspr(SPRN_MMCR0, mmcr0);
 }