diff options
| author | Peter Zijlstra <peterz@infradead.org> | 2014-06-24 14:48:19 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-07-28 08:08:27 -0700 |
| commit | 6cb66ebf030b998799ba491e88ef95eca2895bd7 (patch) | |
| tree | f92ce646c612ad1682481dcccd8426428ff6605e | |
| parent | f7eb924e4e591ead2e07dc9f2fabfaa5c4a6c31c (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.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 57e5ce126d5..ea030319b32 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; } |