On 17-06-2014 13:15, Peter Zijlstra wrote: > On Mon, Jun 16, 2014 at 10:43:38PM +0530, Viresh Kumar wrote: >> Cc'ing Mauro/Rafael/Srivatsa.. >> >> On Thu, Dec 12, 2013 at 7:38 PM, Peter Zijlstra <pet...@infradead.org> wrote: >>> Use a ring-buffer like multi-version object structure which allows >>> always having a coherent object; we use this to avoid having to >>> disable IRQs while reading sched_clock() and avoids a problem when >>> getting an NMI while changing the cyc2ns data. >>> >>> MAINLINE PRE POST >>> >>> sched_clock_stable: 1 1 1 >>> (cold) sched_clock: 329841 331312 257223 >>> (cold) local_clock: 301773 310296 309889 >>> (warm) sched_clock: 38375 38247 25280 >>> (warm) local_clock: 100371 102713 85268 >>> (warm) rdtsc: 27340 27289 24247 >>> sched_clock_stable: 0 0 0 >>> (cold) sched_clock: 382634 372706 301224 >>> (cold) local_clock: 396890 399275 399870 >>> (warm) sched_clock: 38194 38124 25630 >>> (warm) local_clock: 143452 148698 129629 >>> (warm) rdtsc: 27345 27365 24307 >>> >>> Signed-off-by: Peter Zijlstra <pet...@infradead.org> >>> --- >>> arch/x86/include/asm/timer.h | 23 +++ >>> arch/x86/kernel/cpu/perf_event.c | 14 +- >>> arch/x86/kernel/tsc.c | 229 >>> ++++++++++++++++++++++++++++++++++----- >>> 3 files changed, 236 insertions(+), 30 deletions(-) >> >> Hi Peter, >> >> We have been following a bug around cpufreq changes in 3.14 >> (https://bugzilla.kernel.org/show_bug.cgi?id=77201) and our tests >> narrowed it down to this patch after which things aren't working >> as expected. > >> Mauro (registosi...@hotmail.com) have reported that since 3.14 >> after doing hot-unplug/hotplug of CPU1, cpufreq POSTCHANGE notifications >> for every second frequency change hangs his machine .. > > Ah, just a freeze?
If you mean no output whatsoever and frozen to the point of needing a hard shutdown/reboot, yes. >> Last working tag was: 3.13.8 and it started failing from 3.14 and fails >> for latest 3.15 as well.. >> >> model name : AMD Turion(tm) 64 X2 Mobile Technology TL-64 >> CPUFreq driver: powernow-k8 .. >> CPUs: Only two CPUs, sharing clock line > > What's specific to this particular CPU? That is a very good question, for which I don't have an answer, as far as I know it is just like any other AMD mobile Turion X2 cpu. >> Can you give any pointers, so that he can get it fixed ? > > So what you can try is force a cyc2ns read before the write in > set_cyc2ns_scale(). I think its possible that if we do not do the read, > the write will wait for a 'free' slot indefinitely. For that I'll need some help/pointers.
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