From 6fdcb26a89c847ce31c001015a447cec6c0d21bb Mon Sep 17 00:00:00 2001
From: Robert Richter <robert.richter@amd.com>
Date: Mon, 2 Apr 2012 20:19:15 +0200
Subject: [PATCH] --- yaml --- r: 304891 b: refs/heads/master c:
 7caaf4d8241feecafb87919402b0a6dbb1b71d9e h: refs/heads/master i:   304889:
 555852818b99acac422a677b5a3ce35e06bdceef   304887:
 26fe21c61939cf74c4fe1473b605693240684d0f v: v3

---
 [refs]                                         |  2 +-
 trunk/arch/x86/kernel/cpu/perf_event_amd_ibs.c | 15 +++++++++++++--
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/[refs] b/[refs]
index d422b426a400..76c5495863da 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: fc006cf7cc7471e1bdf34e40111971e03622af6c
+refs/heads/master: 7caaf4d8241feecafb87919402b0a6dbb1b71d9e
diff --git a/trunk/arch/x86/kernel/cpu/perf_event_amd_ibs.c b/trunk/arch/x86/kernel/cpu/perf_event_amd_ibs.c
index 3e32908292a7..cb51a3e55870 100644
--- a/trunk/arch/x86/kernel/cpu/perf_event_amd_ibs.c
+++ b/trunk/arch/x86/kernel/cpu/perf_event_amd_ibs.c
@@ -85,8 +85,19 @@ perf_event_set_period(struct hw_perf_event *hwc, u64 min, u64 max, u64 *hw_perio
 		overflow = 1;
 	}
 
-	if (left > max)
-		left = max;
+	/*
+	 * If the hw period that triggers the sw overflow is too short
+	 * we might hit the irq handler. This biases the results.
+	 * Thus we shorten the next-to-last period and set the last
+	 * period to the max period.
+	 */
+	if (left > max) {
+		left -= max;
+		if (left > max)
+			left = max;
+		else if (left < min)
+			left = min;
+	}
 
 	*hw_period = (u64)left;