[Crash-utility] Broken backtrace with nested NMIs

[oliver yang]

2014-04-29 19:27 GMT+08:00 Petr Tesarik <ptesarik at suse.cz>:

>
> It will show an incorrect register dump, but the backtrace continues.
> For example:
>

Hi Petr,

The back trace looks good.

How did you know the register dump is incorrect?

At least the value of RSP saved in NMI stack seemed to be good,

RSP: ffff880232b2ff18

Recently, I'm working on a core file analysis, and found crash tool
couldn't give the correct NMI back trace.
But I can find right stack trace by using IST pointer.

I'm wondering whether your patch could work for my cases.

May I can try your fix after it is ready.


>
> PID: 0      TASK: ffff880232b2c440  CPU: 7   COMMAND: "kworker/0:1"
>  #0 [ffff88023fdc7e40] crash_nmi_callback at ffffffff8102428f
>  #1 [ffff88023fdc7e50] notifier_call_chain at ffffffff81461ec7
>  #2 [ffff88023fdc7e80] __atomic_notifier_call_chain at ffffffff81461f0d
>  #3 [ffff88023fdc7e90] notify_die at ffffffff81461f5d
>  #4 [ffff88023fdc7ec0] default_do_nmi at ffffffff8145f3a7
>  #5 [ffff88023fdc7ee0] do_nmi at ffffffff8145f5d8
>  #6 [ffff88023fdc7ef0] restart_nmi at ffffffff8145eb2d
>     [exception RIP: mwait_idle+423]
>     RIP: ffffffff8100b217  RSP: ffff880232b2ff18  RFLAGS: 00000246
>     RAX: 0000000000000010  RBX: 0000000000000010  RCX: 0000000000000246
>     RDX: ffff880232b2ff18  RSI: 0000000000000018  RDI: 0000000000000001
>     RBP: ffffffff8100b217   R8: ffffffff8100b217   R9: 0000000000000018
>     R10: ffff880232b2ff18  R11: 0000000000000246  R12: ffffffffffffffff
>     R13: ffffffff81d36108  R14: ffff880232b2ffd8  R15: 0000000000000000
>     ORIG_RAX: 0000000000000000  CS: 0010  SS: 0018
> --- <NMI exception stack> ---
>  #7 [ffff880232b2ff18] mwait_idle at ffffffff8100b217
>  #8 [ffff880232b2ff30] cpu_idle at ffffffff81002126
>
> If there is a nested NMI, reading the code suggests crash may loop again
> to the NMI stack, but I don't have a sample dump file ATM.
>
> Petr T
>
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-- 
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Oliver Yang
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