linux-kernel - Re: [PATCH] sched: fix need_resched() when checking peempt

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: <BANLkTi=-c_XQOP4FAQEH6FN-9D62HS+tLw@mail.gmail.com>
Date:	Wed, 25 May 2011 11:24:30 +0800
From:	Yong Zhang <yong.zhang0@...il.com>
To:	Hillf Danton <dhillf@...il.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	Mike Galbraith <efault@....de>
Subject: Re: [PATCH] sched: fix need_resched() when checking peempt

On Tue, May 24, 2011 at 9:50 PM, Hillf Danton <dhillf@...il.com> wrote:
> On Tue, May 24, 2011 at 9:39 PM, Steven Rostedt <rostedt@...dmis.org> wrote:
>> On Tue, 2011-05-24 at 21:27 +0800, Hillf Danton wrote:
>>> When checking if current task could be preempted by a newly woken task,
>>> further check could be bypassed if the current thread is different from
>>> the current task of run-queue, and it is corrected accordingly.
>>
>> Ug, that change log is an obfuscated mess. But looking at the actual
>> patch, I figured what you wanted to say. How about this:
>>
>> ----
>> The RT preempt check tests the wrong task if NEED_RESCHED is set. It
>> currently checks the local CPU task. It is suppose to check the task
>> that is running on the run queue we are about to wake another task on.
>> ----
>>
> Thanks, it is great changelog:)

Good catch.

Reviewed-by: Yong Zhang <yong.zhang0@...il.com>

BTW, this may be the reason for we could trigger
WARN_ON_ONCE(test_tsk_need_resched(next));
https://lkml.org/lkml/2010/12/20/28

Peter, Mike, how do you think about it?

Thanks,
Yong


-- 
Only stand for myself
--
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/