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Message-ID: <46079698.2070506@boichat.ch> Date: Mon, 26 Mar 2007 17:47:04 +0800 From: Nicolas Boichat <nicolas@...chat.ch> To: Ingo Molnar <mingo@...e.hu> CC: Linus Torvalds <torvalds@...ux-foundation.org>, Michal Piotrowski <michal.k.k.piotrowski@...il.com>, linux-kernel@...r.kernel.org Subject: Re: [BUG] Macbook pro timer bug (was: "Patch "CPU hotplug: call check_tsc_sync_source() with irqs off" breaks some drivers") Ingo Molnar wrote: > * Nicolas Boichat <nicolas@...chat.ch> wrote: > > >>> I found out which commit seems to cause these bugs: >>> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=d04f41e35343f1d788551fd3f753f51794f4afcf >>> >>> The latest GIT without this commit works fine, but doesn't with it. >>> >> Sorry about blaming this commit. The problems happen randomly (about 1 >> reboot over 2 is ok, at least with 2.6.21-rc4). I'll run more tests >> and post the results later. >> > > is this the 32-bit kernel? Yes it is. > If yes then does commit > 4edc5db83f574dfcc8be35b7b96760ded543b360 (included in -rc5) fix it? > I don't know precisely which commit you are talking about, but I upgraded to 2.6.21-rc5, and the problem became more obvious. >From what I experimented, I came to the conclusion that when the frequency of the first CPU is wrongly detected, the timers get wrong (i.e. tsc, hpet, with or without high-res timers). It is not a new bug, it happened in 2.6.20 too (I also found an old dmesg from 2.6.18-rc2 with the same frequency detection problem), except that for some reasons it didn't cause that many obvious bugs, so I didn't notice it at that time. (in case you don't remember my first message, I have a Macbook Pro first generation (Core Duo, so x86), see below for /proc/cpuinfo) This is the diff of two consecutive soft reboots, with the same kernel (CONFIG_HPET_TIMER unset, CONFIG_HIGH_RES_TIMERS set): --- dmesg-2.6.21-rc5-nohpet-error-notime 2007-03-26 16:42:00.000000000 +0800 +++ dmesg-2.6.21-rc5-nohpet-success-notime 2007-03-26 16:42:09.000000000 +0800 @@ -100,7 +100,7 @@ Enabling unmasked SIMD FPU exception support... done. Initializing CPU#0 PID hash table entries: 4096 (order: 12, 16384 bytes) -Detected 1952.283 MHz processor. +Detected 1830.920 MHz processor. Console: colour VGA+ 80x25 Dentry cache hash table entries: 131072 (order: 7, 524288 bytes) Inode-cache hash table entries: 65536 (order: 6, 262144 bytes) The "+" boot reports the correct CPU frequency (1.83Ghz). When you run something like this on both: # ntpdate swisstime.ethz.ch # ntpdate swisstime.ethz.ch # sleep 60 # ntpdate swisstime.ethz.ch You get, with the "+" boot, what you expect: 26 Mar 16:33:34 ntpdate[3385]: adjust time server 129.132.2.21 offset 0.120391 sec 26 Mar 16:32:52 ntpdate[3376]: adjust time server 129.132.2.21 offset 0.137979 sec -- pause of about 60 seconds 26 Mar 16:33:55 ntpdate[3386]: adjust time server 129.132.2.21 offset 0.125751 sec i.e. the clock is still correct 60 seconds after you adjust it. While, with the "-" boot, you get: 26 Mar 16:18:05 ntpdate[3444]: step time server 129.132.2.21 offset 3.829351 sec 26 Mar 16:18:08 ntpdate[3445]: adjust time server 129.132.2.21 offset 0.232023 sec -- pause 26 Mar 16:19:16 ntpdate[3447]: step time server 129.132.2.21 offset 4.320653 sec The clock has shifted of about 4.1 seconds in 60 seconds, i.e. an error of 6.8%, which is in the same range as the error between 1952 and 1833 Mhz (6.5%). I get the same results with both CONFIG_HPET_TIMER and CONFIG_HIGH_RES_TIMERS unset, some boots are ok, some aren't. I couldn't get a correct boot with these two options enabled, but it's probably because I didn't reboot enough times... I you want some detailed kernel logs, see http://www.boichat.ch/nicolas/linux/2nd/ . Please tell me if you need more informations, or if you prefer I file a bug in the bugzilla. Best regards, Nicolas --- /proc/cpuinfo on an incorrect boot: nunuche ~ # cat /proc/cpuinfo processor : 0 vendor_id : GenuineIntel cpu family : 6 model : 14 model name : Genuine Intel(R) CPU T2400 @ 1.83GHz stepping : 8 cpu MHz : 1952.216 cache size : 2048 KB physical id : 0 siblings : 2 core id : 0 cpu cores : 2 fdiv_bug : no hlt_bug : no f00f_bug : no coma_bug : no fpu : yes fpu_exception : yes cpuid level : 10 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx constant_tsc pni monitor vmx est tm2 xtpr bogomips : 4689.63 clflush size : 64 processor : 1 vendor_id : GenuineIntel cpu family : 6 model : 14 model name : Genuine Intel(R) CPU T2400 @ 1.83GHz stepping : 8 cpu MHz : 1952.216 cache size : 2048 KB physical id : 0 siblings : 2 core id : 1 cpu cores : 2 fdiv_bug : no hlt_bug : no f00f_bug : no coma_bug : no fpu : yes fpu_exception : yes cpuid level : 10 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx constant_tsc pni monitor vmx est tm2 xtpr bogomips : 3661.27 clflush size : 64 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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