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Date: Fri, 26 Sep 2008 00:04:30 +0530 From: Tej <bewith.tej@...il.com> To: "Cyrill Gorcunov" <gorcunov@...il.com> Cc: "Jason Wessel" <jason.wessel@...driver.com>, linux-kernel@...r.kernel.org Subject: Re: Kernel PANIC with 2.6.27-rc6 On 9/25/08, Cyrill Gorcunov <gorcunov@...il.com> wrote: > [Cyrill Gorcunov - Thu, Sep 25, 2008 at 06:56:35PM +0400] > | [Tej - Thu, Sep 25, 2008 at 08:05:23PM +0530] > | | On 9/11/08, Jason Wessel <jason.wessel@...driver.com> wrote: > | | > Tej wrote: > | | >> observed a panic on 2.6.27-rc6 caused by enabling > | | >> "CONFIG_KGDB_TESTS_ON_BOOT" option > | | >> > | | >> panic logged using serial console and .config are attached. > | | >> > | | >> Linux version 2.6.27-rc6 (root@...er-desktop) (gcc version 4.2.3 > | | > (Ubuntu 4.2.3-8 > | | > [clip] > | | >> kgdb: Registered I/O driver kgdbts. > | | >> kgdbts:RUN plant and detach test > | | >> kgdbts:RUN sw breakpoint test > | | >> kgdbts:RUN bad memory access test > | | >> kgdbts:RUN singlestep test 1000 iterations > | | >> kgdbts:RUN singlestep [0/1000] > | | >> kgdbts:RUN singlestep [100/1000] > | | >> kgdbts: BP mismatch c0109c02 expected c02ad250 > | | > > | | > > | | > > | | > So if we break this down into what it means, the kgdb test got an > | | > exception and stopped somewhere other than where it placed the > | | > breakpoint. In this case 0xc0109c02 which you can see right after the > | | > text "BP mismatch". > | | > | | i have obsvered this bug from 2.6.27-rc1 to rc7 > | | however the 2.6.26 was fine > | | > | | > | | > > | | > This address is in your stack trace below (read on) > | | > | | > > | | > > | | >> ------------[ cut here ]------------ > | | >> WARNING: at drivers/misc/kgdbts.c:302 check_and_rewind_pc+0xb2/0xe0() > | | >> Modules linked in: > | | >> Pid: 0, comm: swapper Not tainted 2.6.27-rc6 #16 > | | >> [<c0125d04>] warn_on_slowpath+0x54/0x70 > | | >> [<c01260f0>] ? __call_console_drivers+0x60/0x70 > | | >> [<c013c15b>] ? up+0x2b/0x40 > | | >> [<c0126634>] ? release_console_sem+0x1a4/0x1c0 > | | >> [<c01548f7>] ? __rmqueue_smallest+0xb7/0x130 > | | >> [<c02445e7>] ? __copy_to_user_ll+0x57/0x60 > | | >> [<c0153dc0>] ? probe_kernel_write+0x20/0x40 > | | >> [<c02ad250>] ? kgdbts_break_test+0x0/0x30 > | | >> [<c0126bab>] ? printk+0x1b/0x20 > | | >> [<c02ad250>] ? kgdbts_break_test+0x0/0x30 > | | >> [<c02adfb2>] check_and_rewind_pc+0xb2/0xe0 > | | >> [<c0109c02>] ? mwait_idle+0x32/0x40 > | | > > | | > > | | > So if you were to do: > | | > gdb ./vmlinux > | | > i line *0xc0109c02 > | | > > | | > It will print the line of source that caused the problem. It is > | | > probably the case that this is a victim however, as this looks like > | | > some kind of nmi race condition. > | | > > | | > Perhaps you could confirm this? > | | > | | ok so i did git bisection which pointed:- > | | > | | commit 3ed3f06295e69700fa808396f7b350bff2b69de0 > | | Author: Cyrill Gorcunov <gorcunov@...il.com> > | | Date: Wed Jun 4 01:00:47 2008 +0400 > | | > | | x86: nmi - consolidate nmi_watchdog_default for 32bit mode > | | > | | 64bit mode bootstrap code does set nmi_watchdog to NMI_NONE > | | by default and doing the same on 32bit mode is safe too. > | | Such an action saves us from several #ifdef. > | | > | | > | | > | | git -bisection log. > | | > | | git-bisect start > | | # bad: [6e86841d05f371b5b9b86ce76c02aaee83352298] Linux 2.6.27-rc1 > | | git-bisect bad 6e86841d05f371b5b9b86ce76c02aaee83352298 > | | # good: [bce7f793daec3e65ec5c5705d2457b81fe7b5725] Linux 2.6.26 > | | git-bisect good bce7f793daec3e65ec5c5705d2457b81fe7b5725 > | | # bad: [d20b27478d6ccf7c4c8de4f09db2bdbaec82a6c0] V4L/DVB (8415): > | | gspca: Infinite loop in i2c_w() of etoms. > | | git-bisect bad d20b27478d6ccf7c4c8de4f09db2bdbaec82a6c0 > | | # bad: [666484f0250db2e016948d63b3ef33e202e3b8d0] Merge branch > | | 'core/softirq' of > | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip > | | git-bisect bad 666484f0250db2e016948d63b3ef33e202e3b8d0 > | | # bad: [d59fdcf2ac501de99c3dfb452af5e254d4342886] Merge commit > | | 'v2.6.26' into x86/core > | | git-bisect bad d59fdcf2ac501de99c3dfb452af5e254d4342886 > | | # good: [3de352bbd86f890dd0c5e1c09a6a1b0b29e0f8ce] Merge branch > | | 'x86/mpparse' into x86/devel > | | git-bisect good 3de352bbd86f890dd0c5e1c09a6a1b0b29e0f8ce > | | # bad: [b4df32f4aeef8794d0135fc8dc250acb44cfee60] x86: fix warning in > | | e820_reserve_resources with 32bit > | | git-bisect bad b4df32f4aeef8794d0135fc8dc250acb44cfee60 > | | # bad: [7f0be02c5ed1deb04c54c6a17f412e04f417df11] x86: move > | | boot_params declaring to setup.c > | | git-bisect bad 7f0be02c5ed1deb04c54c6a17f412e04f417df11 > | | # bad: [4b62ac9a2b859f932afd5625362c927111b7dd9b] Merge branch > | | 'x86/nmi' into x86/devel > | | git-bisect bad 4b62ac9a2b859f932afd5625362c927111b7dd9b > | | # bad: [f781b03c4b1c713ac000877c8bbc31fc4164a29b] x86: > | | touch_nmi_watchdog(): reset alert counters for supported nmi_watchdog > | | modes only > | | git-bisect bad f781b03c4b1c713ac000877c8bbc31fc4164a29b > | | # good: [96f9dcb10755e96eae706b9e869c0dc25adb3d74] x86: nmi_64.c - use > | | for_each_possible_cpu helper > | | git-bisect good 96f9dcb10755e96eae706b9e869c0dc25adb3d74 > | | # good: [ba3a5974239293d921235e6fa82b09b670e674ef] - fix typo in > | | include/asm-x86/nmi.h > | | git-bisect good ba3a5974239293d921235e6fa82b09b670e674ef > | | # bad: [3ed3f06295e69700fa808396f7b350bff2b69de0] x86: nmi - > | | consolidate nmi_watchdog_default for 32bit mode > | | git-bisect bad 3ed3f06295e69700fa808396f7b350bff2b69de0 > | | # good: [3d1ba1da2b4ff4ace7801e99fb9a3095b182d847] x86: fix nmi.c build > bug > | | git-bisect good 3d1ba1da2b4ff4ace7801e99fb9a3095b182d847 > | | > | | > | | One more point, this bug i have observed on intel VT machine, on > | | non-VT machine i couldn't able to trigger this bug. > | | > | | cat /proc/cpuinfo | grep vmx > | | > | | flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov > | | pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe lm > | | constant_tsc pni monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr > | | lahf_lm > | | flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov > | | pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe lm > | | constant_tsc pni monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr > | | lahf_lm > | | > | | HTH > | | > | | > | | > | | > | | > | | > | | > | | > > | | > My guess would rougly be arch/x86/kernel/processs.c > | | > > | | > 170 __monitor((void *)¤t_thread_info()->flags, 0, 0); > | | > > | | > And perhaps this is a deference error, or it will be an even less > | | > obvious problem where the return from the nmi kgdb uses to sync the > | | > processors has created some kind of invalid context. This may or may > | | > not be a direct problem with kgdb, but nothing in this area had really > | | > changed since the 2.6.26 kernel. > | | > > | | > Unfortunately I could not reproduce the problem. If you consistently > | | > see this with each boot, but you do not see it on the 2.6.27 rc1 or > | | > 2.6.26 released kernel for instance, it is definitely worth bisecting, > | | > as the problem was caused elsewhere in the kernel. > | | > > | | >> [<c02ad250>] ? kgdbts_break_test+0x0/0x30 > | | >> [<c02acdd1>] validate_simple_test+0x21/0xb0 > | | >> [<c02ad5a7>] run_simple_test+0x107/0x260 > | | >> [<c0153e00>] ? probe_kernel_read+0x20/0x40 > | | >> [<c02acec4>] kgdbts_put_char+0x14/0x20 > | | >> [<c014aa36>] put_packet+0x86/0xe0 > | | >> [<c014b650>] kgdb_handle_exception+0x2f0/0xd90 > | | >> [<c0114cc8>] kgdb_notify+0x58/0x180 > | | >> [<c013c33d>] notifier_call_chain+0x2d/0x60 > | | >> [<c013c38c>] __atomic_notifier_call_chain+0x1c/0x30 > | | >> [<c013c3ba>] atomic_notifier_call_chain+0x1a/0x20 > | | >> [<c013c44d>] notify_die+0x2d/0x30 > | | >> [<c01056ca>] die_nmi+0x3a/0x100 > | | >> [<c0112697>] nmi_watchdog_tick+0x187/0x190 > | | >> [<c0106067>] do_nmi+0x87/0x2a0 > | | >> [<c04d5a73>] nmi_stack_correct+0x26/0x2b > | | >> [<c011007b>] ? msr_seek+0xb/0x80 > | | >> [<c0109c02>] ? mwait_idle+0x32/0x40 > | | >> [<c01026c5>] cpu_idle+0x55/0xf0 > | | >> [<c04ae02e>] rest_init+0x4e/0x60 > | | >> [<c069794f>] start_kernel+0x23f/0x2c0 > | | >> [<c0697270>] ? unknown_bootoption+0x0/0x210 > | | >> [<c0697077>] __init_begin+0x77/0xb0 > | | > > | | > > | | > Jason. > | | > > | | -- > | | 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/ > | | > | > | Thanks for feedback, Tej! Will check this commit. > | > | - Cyrill - > | > > If assume that git bisect is right - it's hardly possible i have bisected it twice n jason mentioned that it looks like some kind of nmi race condition. but i will bisect it again in rc7 and let you know. > that proc_nmi_enabled() related changes introduced this > error (ie this commit) - kgdb seems to be not > touching /proc/sys/kernel/nmi while doing self-tests. > > - Cyrill - > -- 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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