Re: [PATCH] fix BUG using smp_processor_id() in touch_nmi_watchdogand touch_softlockup_watchdog

[Yong Zhang]

On Tue, Aug 17, 2010 at 4:39 PM, Sergey Senozhatsky
<sergey.senozhatsky@xxxxxxxxx> wrote:
>> Why not use __raw_get_cpu_var() instead?
>> You know adding preempt protection in touch_softlockup_watchdog()
>> just suppress the warning. Am I missing something?
>>
>
> Sorry, my low level understanding of the __raw_get_cpu_var isn't very strong.
> I assume it uses current_thread_info()->cpu in some cases (right?) or
> percpu_from_op.

The difference is __raw_get_cpu_var() is using raw_smp_processor_id().

>
>
> Should it be
> acpi_os_stall
> Â Â Â Âpreepmt_disable
> Â Â Â Âtouch_nmi_watchdog
> Â Â Â Â Â Â Â Âtouch_softlockup_watchdog
> Â Â Â Âpreempt_enable

Actually I don't think this is helpful for the whole function. Because
if acpi_os_stall()
migrate(I don't know if it could) to another CPU just before
preepmt_disable(), we'll
be on the wrong way. Adding preempt protection is just smoothing the warning.

So I prefer using __raw_get_cpu_var() as what we have been done before.

Thanks,
Yong
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