This is a note to let you know that I've just added the patch titled
x86, tsc: Fix cpufreq lockup
to the 3.14-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-3.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 3896c329df8092661dac80f55a8c3f60136fd61a Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <[email protected]>
Date: Tue, 24 Jun 2014 14:48:19 +0200
Subject: x86, tsc: Fix cpufreq lockup
From: Peter Zijlstra <[email protected]>
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 <[email protected]>
Tested-by: Mauro <[email protected]>
Fixes: 20d1c86a5776 ("sched/clock, x86: Rewrite cyc2ns() to avoid the need to
disable IRQs")
Cc: "Rafael J. Wysocki" <[email protected]>
Cc: Viresh Kumar <[email protected]>
Cc: Bin Gao <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Mika Westerberg <[email protected]>
Cc: Paul Gortmaker <[email protected]>
Cc: Stefani Seibold <[email protected]>
Cc: [email protected]
Signed-off-by: Peter Zijlstra <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
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
@@ -921,9 +921,9 @@ 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 [email protected] are
queue-3.14/perf-do-not-allow-optimized-switch-for-non-cloned-events.patch
queue-3.14/x86-tsc-fix-cpufreq-lockup.patch
queue-3.14/perf-x86-intel-ignore-condchgd-bit-to-avoid-false-nmi-handling.patch
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