---

yaml
---
r: 252646
b: refs/heads/master
c: d819437
h: refs/heads/master
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 3d2606f42984613d324ad3047cf503bcddc3880a
+refs/heads/master: d819437156fd99da61d4e1402b2dbfc5cc472265

trunk/arch/powerpc/oprofile/op_model_power4.c

@@ -261,6 +261,28 @@ static int get_kernel(unsigned long pc, unsigned long mmcra)
 	return is_kernel;
 }
 
+static bool pmc_overflow(unsigned long val)
+{
+	if ((int)val < 0)
+		return true;
+
+	/*
+	 * Events on POWER7 can roll back if a speculative event doesn't
+	 * eventually complete. Unfortunately in some rare cases they will
+	 * raise a performance monitor exception. We need to catch this to
+	 * ensure we reset the PMC. In all cases the PMC will be 256 or less
+	 * cycles from overflow.
+	 *
+	 * We only do this if the first pass fails to find any overflowing
+	 * PMCs because a user might set a period of less than 256 and we
+	 * don't want to mistakenly reset them.
+	 */
+	if (__is_processor(PV_POWER7) && ((0x80000000 - val) <= 256))
+		return true;
+
+	return false;
+}
+
 static void power4_handle_interrupt(struct pt_regs *regs,
 				    struct op_counter_config *ctr)
 {
@@ -281,7 +303,7 @@ static void power4_handle_interrupt(struct pt_regs *regs,
 
 	for (i = 0; i < cur_cpu_spec->num_pmcs; ++i) {
 		val = classic_ctr_read(i);
-		if (val < 0) {
+		if (pmc_overflow(val)) {
 			if (oprofile_running && ctr[i].enabled) {
 				oprofile_add_ext_sample(pc, regs, i, is_kernel);
 				classic_ctr_write(i, reset_value[i]);