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authorPeter Zijlstra <peterz@infradead.org>2014-06-24 14:48:19 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-07-28 08:06:03 -0700
commit89d30c2107c85ce3ae1a267f1065aa0fb1e5b310 (patch)
treeb0eb6f8f502331c262fce31d34a3e7af41fada9b
parent025d494281c58dcee04fe3ee2b7fa300e150c95c (diff)
x86, tsc: Fix cpufreq lockup
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@hotmail.com> Tested-by: Mauro <registosites@hotmail.com> Fixes: 20d1c86a5776 ("sched/clock, x86: Rewrite cyc2ns() to avoid the need to disable IRQs") Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net> Cc: Viresh Kumar <viresh.kumar@linaro.org> Cc: Bin Gao <bin.gao@intel.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mika Westerberg <mika.westerberg@linux.intel.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Stefani Seibold <stefani@seibold.net> Cc: linux-kernel@vger.kernel.org Signed-off-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--arch/x86/kernel/tsc.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index cfbe99f88830..e0d1d7a8354e 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -921,9 +921,9 @@ static int time_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
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;
}