linux-kernel - Re: [PATCH] fix BUG using smp_processor_id() in touch_nmi_watchdog and touch_softlockup

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <AANLkTikjR1nC3DYdvSw=FEmAVZ98=ju2RNq-MF1L7U3u@mail.gmail.com>
Date:	Tue, 17 Aug 2010 17:37:34 +0800
From:	Yong Zhang <yong.zhang0@...il.com>
To:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Don Zickus <dzickus@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fix BUG using smp_processor_id() in touch_nmi_watchdog
 and touch_softlockup_watchdog

On Tue, Aug 17, 2010 at 5:24 PM, Sergey Senozhatsky
<sergey.senozhatsky@...il.com> wrote:
> OK. Suppose (I don't know if it could) migration has happen
>
> acpi_os_stall
>        __migration__
>        touch_nmi_watchdog
>
> How calling raw_smp_processor_id() (which is current_thread_info()->cpu)
> vs. preepmt_disable - smp_processor_id() will give us different CPUs?

I don't mean you will get different CPUS(sorry for my poor english).
I mean if the migration could happen, you want to touch_nmi_watchdog()
on CPU A(otherwise the watchdog will shout on us), but eventually we
touch_nmi_watchdog() on CPU B(because of migration),
and this is not what we want.

So preempt_disable() is redundant here.

>
>> So I prefer using __raw_get_cpu_var() as what we have been done before.
>>
>
> Hm...
>
> 26e09c6eee14f4827b55137ba0eedc4e77cd50ab

f69bcf60c3f17aa367e16eef7bc6ab001ea6d58a
2508ce1845a3b256798532b2c6b7997c2dc6533b

you can get the previous touch_*_watchdog there.

Thanks,
Yong
--
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/