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Date: Sat, 26 Jul 2014 12:02:50 -0700 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, Mauro <registosites@...mail.com>, "Rafael J. Wysocki" <rjw@...ysocki.net>, Viresh Kumar <viresh.kumar@...aro.org>, Bin Gao <bin.gao@...el.com>, Linus Torvalds <torvalds@...ux-foundation.org>, Mika Westerberg <mika.westerberg@...ux.intel.com>, Paul Gortmaker <paul.gortmaker@...driver.com>, Stefani Seibold <stefani@...bold.net>, Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...nel.org> Subject: [PATCH 3.14 76/87] x86, tsc: Fix cpufreq lockup 3.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Peter Zijlstra <peterz@...radead.org> 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@...mail.com> Tested-by: Mauro <registosites@...mail.com> Fixes: 20d1c86a5776 ("sched/clock, x86: Rewrite cyc2ns() to avoid the need to disable IRQs") Cc: "Rafael J. Wysocki" <rjw@...ysocki.net> Cc: Viresh Kumar <viresh.kumar@...aro.org> Cc: Bin Gao <bin.gao@...el.com> Cc: Linus Torvalds <torvalds@...ux-foundation.org> Cc: Mika Westerberg <mika.westerberg@...ux.intel.com> Cc: Paul Gortmaker <paul.gortmaker@...driver.com> Cc: Stefani Seibold <stefani@...bold.net> Cc: linux-kernel@...r.kernel.org Signed-off-by: Peter Zijlstra <peterz@...radead.org> Signed-off-by: Ingo Molnar <mingo@...nel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- 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; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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