Commit-ID: 3896c329df8092661dac80f55a8c3f60136fd61a Gitweb: http://git.kernel.org/tip/3896c329df8092661dac80f55a8c3f60136fd61a Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx> AuthorDate: Tue, 24 Jun 2014 14:48:19 +0200 Committer: Ingo Molnar <mingo@xxxxxxxxxx> CommitDate: Wed, 2 Jul 2014 08:33:47 +0200 x86, tsc: Fix cpufreq lockup 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: <stable@xxxxxxxxxxxxxxx> 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> --- arch/x86/kernel/tsc.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 57e5ce1..ea03031 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -920,9 +920,9 @@ 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; } -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html