From 3c3441ad4ca1f1c0d3af979b1a97d25925bda5af Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date: Tue, 15 Feb 2011 22:26:07 +0100
Subject: [PATCH] --- yaml --- r: 233551 b: refs/heads/master c:
 4fe757dd48a9e95e1a071291f15dda5421dacb66 h: refs/heads/master i:   233549:
 95ed869b04719e272d6bd5be71f16f91677da152   233547:
 0e44b8b551f74b10d2d5f59f942a92c47fb8cc96   233543:
 25c92c1a6563f8f141d9436610a378a9b79d0b13   233535:
 678e63f57ca284d886eb4a2fc9e3bc7625f4e448 v: v3

---
 [refs]                    |  2 +-
 trunk/kernel/perf_event.c | 19 +++++++++++++++----
 2 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/[refs] b/[refs]
index eaaa816501b6..ae96d2da466e 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 7d44ec193d95416d1342cdd86392a1eeb7461186
+refs/heads/master: 4fe757dd48a9e95e1a071291f15dda5421dacb66
diff --git a/trunk/kernel/perf_event.c b/trunk/kernel/perf_event.c
index 999835b6112b..656222fcf767 100644
--- a/trunk/kernel/perf_event.c
+++ b/trunk/kernel/perf_event.c
@@ -782,6 +782,10 @@ void perf_event_disable(struct perf_event *event)
 	raw_spin_unlock_irq(&ctx->lock);
 }
 
+#define MAX_INTERRUPTS (~0ULL)
+
+static void perf_log_throttle(struct perf_event *event, int enable);
+
 static int
 event_sched_in(struct perf_event *event,
 		 struct perf_cpu_context *cpuctx,
@@ -794,6 +798,17 @@ event_sched_in(struct perf_event *event,
 
 	event->state = PERF_EVENT_STATE_ACTIVE;
 	event->oncpu = smp_processor_id();
+
+	/*
+	 * Unthrottle events, since we scheduled we might have missed several
+	 * ticks already, also for a heavily scheduling task there is little
+	 * guarantee it'll get a tick in a timely manner.
+	 */
+	if (unlikely(event->hw.interrupts == MAX_INTERRUPTS)) {
+		perf_log_throttle(event, 1);
+		event->hw.interrupts = 0;
+	}
+
 	/*
 	 * The new state must be visible before we turn it on in the hardware:
 	 */
@@ -1596,10 +1611,6 @@ void __perf_event_task_sched_in(struct task_struct *task)
 	}
 }
 
-#define MAX_INTERRUPTS (~0ULL)
-
-static void perf_log_throttle(struct perf_event *event, int enable);
-
 static u64 perf_calculate_period(struct perf_event *event, u64 nsec, u64 count)
 {
 	u64 frequency = event->attr.sample_freq;