From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Lezcano Subject: Re: CONFIG_NO_HZ + CONFIG_CPU_IDLE freeze the system (Was Re: [PATCH] acpi : remove power from acpi_processor_cx structure) Date: Mon, 10 Sep 2012 21:45:07 +0200 Message-ID: <504E4343.5070004@linaro.org> References: <1343164349-28550-1-git-send-email-daniel.lezcano@linaro.org> <201209062204.11288.rjw@sisk.pl> <50490920.9070204@linaro.org> <201209062318.42874.rjw@sisk.pl> <504A02BD.4000805@linaro.org> <504A2D73.3010702@linaro.org> <504A68A0.7010907@linaro.org> <504E1FE5.6090502@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <504E1FE5.6090502@linaro.org> Sender: linux-kernel-owner@vger.kernel.org To: John Stultz Cc: prarit@redhat.com, xen-devel@lists.xensource.com, linaro-dev@lists.linaro.org, Peter Zijlstra , linux-pm@vger.kernel.org, Frederic Weisbecker , richardcochran@gmail.com, Konrad Rzeszutek Wilk , Linux Kernel Mailing List , "Rafael J. Wysocki" , linux-acpi@vger.kernel.org, Thomas Gleixner , mingo@kernel.org, lenb@kernel.org List-Id: xen-devel@lists.xenproject.org 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=3Dy and CONFIG_CPU_IDLE=3D= 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 >>>> 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 >>>> Reviewed-by: Ingo Molnar >>>> Cc: Peter Zijlstra >>>> Cc: Richard Cochran >>>> Cc: Prarit Bhargava >>>> Link: >>>> http://lkml.kernel.org/r/1342156917-25092-5-git-send-email-john.st= ultz@linaro.org >>>> >>>> >>>> Signed-off-by: Thomas Gleixner >>>> >>>> :040000 040000 4d6541ac1f6075d7adee1eef494b31a0cbda0934 >>>> dc5708bc738af695f092bf822809b13a1da104b6 M kernel >>>> >>>> How to reproduce: with a laptop T61p, with a Core 2 Duo. I boot th= e >>>> kernel in busybox and wait some minutes before writing something i= n >>>> 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. Disabl= ing >>>> 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 question= s: >>> >>> 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 m= e > 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 --=20 Linaro.org =E2=94=82 Open source software for= ARM SoCs =46ollow Linaro: Facebook | Twitter | Blog