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authorPeter Zijlstra <[email protected]>2014-06-24 14:48:19 +0200
committerIngo Molnar <[email protected]>2014-07-02 08:33:47 +0200
commit3896c329df8092661dac80f55a8c3f60136fd61a (patch)
tree02b53e8b429cd1a794a85cabc37d5181fe4d0e9c
parent16874b2cb867d3eb63ed838f2847143e11556708 (diff)
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 <[email protected]> Tested-by: Mauro <[email protected]> Fixes: 20d1c86a5776 ("sched/clock, x86: Rewrite cyc2ns() to avoid the need to disable IRQs") Cc: <[email protected]> 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]>
-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 57e5ce126d5a..ea030319b321 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;
}