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Date: Thu, 25 Sep 2008 19:47:24 +0400 From: Cyrill Gorcunov <gorcunov@...il.com> To: Tej <bewith.tej@...il.com>, Jason Wessel <jason.wessel@...driver.com>, linux-kernel@...r.kernel.org Subject: Re: Kernel PANIC with 2.6.27-rc6 [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 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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