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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] CONFIG_NO_HZ + CONFIG_CPU_IDLE freeze the system (Was Re: [PATCH] acpi : remove power from acpi_processor_cx structure)
On 09/07/2012 07:22 PM, John Stultz wrote: > On 09/07/2012 07:20 AM, Daniel Lezcano wrote: >> On 09/06/2012 11:18 PM, Rafael J. Wysocki wrote: >>> On Thursday, September 06, 2012, Daniel Lezcano wrote: >>>> On 09/06/2012 10:04 PM, Rafael J. Wysocki wrote: >>>>> On Thursday, September 06, 2012, Daniel Lezcano wrote: >>>>>> On 09/06/2012 09:54 AM, Daniel Lezcano wrote: >>>>>> I fall into this issue because NETCONSOLE is set, disabling it >>>>>> allowed >>>>>> me to go further. >>>>>> >>>>>> Unfortunately I am facing to some random freeze on the system which >>>>>> seems to be related to CONFIG_NO_HZ=y and CONFIG_CPU_IDLE=y. >>>>>> >>>>>> Disabling one of them, make the freezes to disappear. >>>>>> >>>>>> Is it a known issue ? >>>>> Well, there are systems having problems with this configuration, >>>>> but they >>>>> should be exceptional. What system is that? >>>> It is a laptop T61p with a Core 2 Duo T9500. Nothing exceptional I >>>> believe. Maybe someone got the same issue ? >>> Is it a regression for you? >> Yes, I think so. The issue appears between v3.5 and v3.6-rc1. >> >> It is not easy to reproduce but after taking some time to dig, it seems >> to appear with this commit: >> >> 1e75fa8be9fb61e1af46b5b3b176347a4c958ca1 is the first bad commit >> commit 1e75fa8be9fb61e1af46b5b3b176347a4c958ca1 >> Author: John Stultz <john.stultz@xxxxxxxxxx> >> Date: Fri Jul 13 01:21:53 2012 -0400 >> >> time: Condense timekeeper.xtime into xtime_sec >> >> The timekeeper struct has a xtime_nsec, which keeps the >> sub-nanosecond remainder. This ends up being somewhat >> duplicative of the timekeeper.xtime.tv_nsec value, and we >> have to do extra work to keep them apart, copying the full >> nsec portion out and back in over and over. >> >> This patch simplifies some of the logic by taking the timekeeper >> xtime value and splitting it into timekeeper.xtime_sec and >> reuses the timekeeper.xtime_nsec for the sub-second portion >> (stored in higher res shifted nanoseconds). >> >> This simplifies some of the accumulation logic. And will >> allow for more accurate timekeeping once the vsyscall code >> is updated to use the shifted nanosecond remainder. >> >> Signed-off-by: John Stultz <john.stultz@xxxxxxxxxx> >> Reviewed-by: Ingo Molnar <mingo@xxxxxxxxxx> >> Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> >> Cc: Richard Cochran <richardcochran@xxxxxxxxx> >> Cc: Prarit Bhargava <prarit@xxxxxxxxxx> >> Link: >> http://lkml.kernel.org/r/1342156917-25092-5-git-send-email-john.stultz@xxxxxxxxxx >> >> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> >> >> :040000 040000 4d6541ac1f6075d7adee1eef494b31a0cbda0934 >> dc5708bc738af695f092bf822809b13a1da104b6 M kernel >> >> How to reproduce: with a laptop T61p, with a Core 2 Duo. I boot the >> kernel in busybox and wait some minutes before writing something in the >> console. At this moment, nothing appears to the console but the >> characters are echo'ed several seconds later (could be 1, 5, or 10 secs >> or more). >> >> That happens when CONFIG_CPU_IDLE and CONFIG_NO_HZ are set. Disabling >> one of them, the issue does not appear. > > Thanks for bisecting this down and the heads up! > > Right off I can't see what might be causing this. Bunch of questions: > > Is this a 32 or 64 bit kernel? It is a 32 bit kernel. > By your description above, it sounds like the system is still > functioning, but there's just a high latency for key-input. Is that right? Yes that's correct but not only. During this freeze time, I can't ping the host. When the output is echo'ed, the ping works again. But if I ping the host indefinitely, it does not freeze and the console is echo'ed without problem. > Are other things on the system happening slowly? I have a very minimal system but at the first glance when it is not frozen > Does generating interrupts by hitting/holding down the ctrl key make the > system respond faster? no. > Is there any dmesg output near when it occurs? no. > If you don't wait that minute after boot before typing anything, does it > still trigger later? (or is it tied to early boot?) That depends, that could happen immediately or later. It is more or less random. > On a whim, does the patch below avoid the problem? Nope, same issue :/ Thanks -- Daniel > > thanks > -john > > diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c > index 34e5eac..2fa0e52 100644 > --- a/kernel/time/timekeeping.c > +++ b/kernel/time/timekeeping.c > @@ -1179,6 +1179,7 @@ static void update_wall_time(void) > timekeeping_adjust(tk, offset); > > > +#if 0 > /* > * Store only full nanoseconds into xtime_nsec after rounding > * it up and add the remainder to the error difference. > @@ -1192,6 +1193,7 @@ static void update_wall_time(void) > tk->xtime_nsec -= remainder; > tk->xtime_nsec += 1ULL << tk->shift; > tk->ntp_error += remainder << tk->ntp_error_shift; > +#endif > > /* > * Finally, make sure that after the rounding > -- <http://www.linaro.org/> Linaro.org â Open source software for ARM SoCs Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook | <http://twitter.com/#!/linaroorg> Twitter | <http://www.linaro.org/linaro-blog/> Blog _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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