Re: cpu offline causes backtrace from cmci_rediscover

[Chen Gong]

On Tue, Mar 19, 2013 at 06:44:08PM -0400, Dave Jones wrote:
> Date:	Tue, 19 Mar 2013 18:44:08 -0400
> From: Dave Jones <davej@xxxxxxxxxx>
> To: Linux Kernel <linux-kernel@xxxxxxxxxxxxxxx>
> Cc: x86@xxxxxxxxxx
> Subject: cpu offline causes backtrace from cmci_rediscover
> User-Agent: Mutt/1.5.21 (2010-09-15)
> 
> offlining a CPU in 3.9-rc3 gets me this trace..
> 
> numa_remove_cpu cpu 1 node 0: mask now 0,2-3
> smpboot: CPU 1 is now offline
> BUG: using smp_processor_id() in preemptible [00000000] code: cpu-offline.sh/10591
> caller is cmci_rediscover+0x6a/0xe0
> Pid: 10591, comm: cpu-offline.sh Not tainted 3.9.0-rc3+ #2
> Call Trace:
>  [<ffffffff81333bbd>] debug_smp_processor_id+0xdd/0x100
>  [<ffffffff8101edba>] cmci_rediscover+0x6a/0xe0
>  [<ffffffff815f5b9f>] mce_cpu_callback+0x19d/0x1ae
>  [<ffffffff8160ea66>] notifier_call_chain+0x66/0x150
>  [<ffffffff8107ad7e>] __raw_notifier_call_chain+0xe/0x10
>  [<ffffffff8104c2e3>] cpu_notify+0x23/0x50
>  [<ffffffff8104c31e>] cpu_notify_nofail+0xe/0x20
>  [<ffffffff815ef082>] _cpu_down+0x302/0x350
>  [<ffffffff815ef106>] cpu_down+0x36/0x50
>  [<ffffffff815f1c9d>] store_online+0x8d/0xd0
>  [<ffffffff813edc48>] dev_attr_store+0x18/0x30
>  [<ffffffff81226eeb>] sysfs_write_file+0xdb/0x150
>  [<ffffffff811adfb2>] vfs_write+0xa2/0x170
>  [<ffffffff811ae16c>] sys_write+0x4c/0xa0
>  [<ffffffff81613019>] system_call_fastpath+0x16/0x1b
> 
Try this patch:

diff a/arch/x86/kernel/cpu/mcheck/mce_intel.c b/arch/x86/kernel/cpu/mcheck/mce_intel.c
index 402c454..692c91e 100644
--- a/arch/x86/kernel/cpu/mcheck/mce_intel.c
+++ b/arch/x86/kernel/cpu/mcheck/mce_intel.c
@@ -311,10 +311,12 @@ void cmci_rediscover(int dying)
                if (cpu == dying)
                        continue;

-               if (cpu == smp_processor_id()) {
+               if (cpu == get_cpu()) {
+                       put_cpu();
                        cmci_rediscover_work_func(NULL);
                        continue;
-               }
+               } else
+                       put_cpu();

                work_on_cpu(cpu, cmci_rediscover_work_func, NULL);
        }

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