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From: Stephane Eranian <eranian@google.com>
To: linux-kernel@vger.kernel.org
Cc: peterz@infradead.org, mingo@elte.hu, dave.hansen@linux.intel.com,
	ak@linux.intel.com, jolsa@redhat.com
Subject: [PATCH] perf: fix interrupt handler timing harness
Date: Fri, 5 Jul 2013 00:30:11 +0200	[thread overview]
Message-ID: <20130704223010.GA30625@quad> (raw)


This patch fixes a serious bug in:

commit 14c63f17b1fde5a575a28e96547a22b451c71fb5
Author: Dave Hansen <dave.hansen@linux.intel.com>
Date:   Fri Jun 21 08:51:36 2013 -0700

    perf: Drop sample rate when sampling is too slow
    

There was an misunderstanding on the API of the do_div()
macro. It returns the remainder of the division and this
was not what the function expected leading to disabling the
interrupt latency watchdog.

This patch also remove a duplicate assignment in
perf_sample_event_took().

Signed-off-by: Stephane Eranian <eranian@google.com>
---

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 1db3af9..1833bc5 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -182,7 +182,7 @@ void update_perf_cpu_limits(void)
 	u64 tmp = perf_sample_period_ns;
 
 	tmp *= sysctl_perf_cpu_time_max_percent;
-	tmp = do_div(tmp, 100);
+	do_div(tmp, 100);
 	atomic_set(&perf_sample_allowed_ns, tmp);
 }
 
@@ -232,7 +232,7 @@ DEFINE_PER_CPU(u64, running_sample_length);
 void perf_sample_event_took(u64 sample_len_ns)
 {
 	u64 avg_local_sample_len;
-	u64 local_samples_len = __get_cpu_var(running_sample_length);
+	u64 local_samples_len;
 
 	if (atomic_read(&perf_sample_allowed_ns) == 0)
 		return;

             reply	other threads:[~2013-07-04 22:30 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-07-04 22:30 Stephane Eranian [this message]
2013-07-05  6:54 ` Ingo Molnar
2013-07-05  9:54 ` [tip:perf/urgent] perf: Fix " tip-bot for Stephane Eranian
2013-07-08 14:34 ` [PATCH] perf: fix " Dave Hansen
2013-07-08 18:08   ` Stephane Eranian
2013-07-08 20:05     ` Dave Hansen
2013-07-08 20:20       ` Stephane Eranian
2013-07-08 20:34         ` Dave Hansen
2013-07-08 20:54           ` Andi Kleen
2013-07-08 20:56             ` Stephane Eranian

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