| Message ID | 504A2D73.3010702@linaro.org (mailing list archive) |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
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@linaro.org> >> 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@linaro.org> >> Reviewed-by: Ingo Molnar <mingo@kernel.org> >> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> >> Cc: Richard Cochran <richardcochran@gmail.com> >> Cc: Prarit Bhargava <prarit@redhat.com> >> Link: >> http://lkml.kernel.org/r/1342156917-25092-5-git-send-email-john.stultz@linaro.org >> >> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> >> >> :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 >
On 09/07/2012 02:35 PM, Daniel Lezcano wrote: > 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@linaro.org> >>> 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@linaro.org> >>> Reviewed-by: Ingo Molnar <mingo@kernel.org> >>> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> >>> Cc: Richard Cochran <richardcochran@gmail.com> >>> Cc: Prarit Bhargava <prarit@redhat.com> >>> Link: >>> http://lkml.kernel.org/r/1342156917-25092-5-git-send-email-john.stultz@linaro.org >>> >>> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> >>> >>> :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. Thanks for your answers! Has this has been seen on 3.6-rc4+ kernels? There were a few casting fixes that landed in 3.6-rc4 that would affect 32bit systems. In the meantime, I'll try to reproduce on my T61. If you could send me your .config, I'd appreciate it. thanks! -john -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 09/10/2012 07:14 PM, John Stultz wrote: > On 09/07/2012 02:35 PM, Daniel Lezcano wrote: >> 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@linaro.org> >>>> 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@linaro.org> >>>> Reviewed-by: Ingo Molnar <mingo@kernel.org> >>>> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> >>>> Cc: Richard Cochran <richardcochran@gmail.com> >>>> Cc: Prarit Bhargava <prarit@redhat.com> >>>> Link: >>>> http://lkml.kernel.org/r/1342156917-25092-5-git-send-email-john.stultz@linaro.org >>>> >>>> >>>> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> >>>> >>>> :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. > > Thanks for your answers! Has this has been seen on 3.6-rc4+ kernels? > There were a few casting fixes that landed in 3.6-rc4 that would > affect 32bit systems. Ok, I have to check that. Unfortunately not before Wednesday. > > In the meantime, I'll try to reproduce on my T61. If you could send me > your .config, I'd appreciate it. http://pastebin.com/qSxqfdDK The header of the config file shows for a v3.5-rc7 because it is the result of the git-bisect. If you keep this config file for the latest kernel that should reproduce the problem. Let me know if you were able to reproduce the problem. Thanks -- Daniel
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