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From: Rui Wang <rui.y.wang@intel.com>
To: bp@suse.de, tony.luck@intel.com, gong.chen@intel.com
Cc: linux-kernel@vger.kernel.org, Rui Wang <rui.y.wang@intel.com>
Subject: MCE bug?
Date: Wed, 17 Jun 2015 09:57:14 +0800
Message-Id: <1434506234-610-1-git-send-email-rui.y.wang@intel.com>
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Hi Boris & Tony,

While injecting MCEs using einj, I encountered a panic:

[    0.305697] mce: CPU supports 22 MCE banks
[    0.310288] BUG: unable to handle kernel NULL pointer dereference at 00000000                                                       00000100
[    0.319057] IP: [<ffffffff8107d0f2>] __queue_work+0x32/0x370
[    0.325398] PGD 0
[    0.327656] Oops: 0000 [#1] SMP

...

[    0.484045] Call Trace:
[    0.486780]  [<ffffffff8107d66b>] queue_work_on+0x2b/0x50
[    0.492821]  [<ffffffff8102e019>] mce_schedule_work.part.16+0x29/0x30
[    0.500020]  [<ffffffff8102f0d9>] machine_check_poll+0x249/0x260
[    0.506733]  [<ffffffff8102f123>] __mcheck_cpu_init_generic+0x33/0x100
[    0.514018]  [<ffffffff81030061>] mcheck_cpu_init+0x161/0x4b0
[    0.520443]  [<ffffffff81016095>] identify_cpu+0x365/0x450
[    0.526576]  [<ffffffff81b6144c>] identify_boot_cpu+0x10/0x7e
[    0.532994]  [<ffffffff81b614ee>] check_bugs+0x9/0x2d
[    0.538643]  [<ffffffff81b5b0a7>] start_kernel+0x469/0x495
[    0.544771]  [<ffffffff81b5aa2e>] ? set_init_arg+0x55/0x55
[    0.550900]  [<ffffffff81b5a120>] ? early_idt_handlers+0x120/0x120
[    0.557805]  [<ffffffff81b5a5ca>] x86_64_start_reservations+0x2a/0x2c
[    0.565001]  [<ffffffff81b5a709>] x86_64_start_kernel+0x13d/0x14c

It happened after the machine rebooted  (due to an injected fatal error). It tried to find leftover banks and then called mce_schedule_work() in machine_check_poll(), but it seemed too early and system_wq wasn't allocated yet, thus the NULL pointer.

Is it a known problem? I'm based on Linux 4.1.0-rc3-7.

Thanks
Rui


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