This is a note to let you know that I've just added the patch titled
x86, tsc: Fix cpufreq lockup
to the 3.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-tsc-fix-cpufreq-lockup.patch
and it can be found in the queue-3.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 3896c329df8092661dac80f55a8c3f60136fd61a Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Date: Tue, 24 Jun 2014 14:48:19 +0200
Subject: x86, tsc: Fix cpufreq lockup
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
commit 3896c329df8092661dac80f55a8c3f60136fd61a upstream.
Mauro reported that his AMD X2 using the powernow-k8 cpufreq driver
locked up when doing cpu hotplug.
Because we called set_cyc2ns_scale() from the time_cpufreq_notifier()
unconditionally, it gets called multiple times for each freq change,
instead of only the once, when the tsc_khz value actually changes.
Because it gets called more than once, we run out of cyc2ns data slots
and stall, waiting for a free one, but because we're half way offline,
there's no consumers to free slots.
By placing the call inside the condition that actually changes tsc_khz
we avoid superfluous calls and avoid the problem.
Reported-by: Mauro <registosites@xxxxxxxxxxx>
Tested-by: Mauro <registosites@xxxxxxxxxxx>
Fixes: 20d1c86a5776 ("sched/clock, x86: Rewrite cyc2ns() to avoid the need to disable IRQs")
Cc: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx>
Cc: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
Cc: Bin Gao <bin.gao@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
Cc: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
Cc: Stefani Seibold <stefani@xxxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kernel/tsc.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -920,9 +920,9 @@ static int time_cpufreq_notifier(struct
tsc_khz = cpufreq_scale(tsc_khz_ref, ref_freq, freq->new);
if (!(freq->flags & CPUFREQ_CONST_LOOPS))
mark_tsc_unstable("cpufreq changes");
- }
- set_cyc2ns_scale(tsc_khz, freq->cpu);
+ set_cyc2ns_scale(tsc_khz, freq->cpu);
+ }
return 0;
}
Patches currently in stable-queue which might be from peterz@xxxxxxxxxxxxx are
queue-3.15/perf-do-not-allow-optimized-switch-for-non-cloned-events.patch
queue-3.15/x86-tsc-fix-cpufreq-lockup.patch
queue-3.15/perf-x86-intel-ignore-condchgd-bit-to-avoid-false-nmi-handling.patch
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