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Subject: Re: [workqueue] d5bff968ea:
 WARNING:at_kernel/workqueue.c:#process_one_work
To:     paulmck@kernel.org, Hillf Danton <hdanton@sina.com>
Cc:     Oliver Sang <oliver.sang@intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Lai Jiangshan <laijs@linux.alibaba.com>,
        LKML <linux-kernel@vger.kernel.org>, lkp@intel.com,
        lkp <lkp@lists.01.org>
References: <20210126073925.1962-1-hdanton@sina.com>
 <20210127092128.2299-1-hdanton@sina.com>
 <20210128090905.1596-1-hdanton@sina.com>
 <20210128180821.GA24510@paulmck-ThinkPad-P72>
From:   Xing Zhengjun <zhengjun.xing@linux.intel.com>
Message-ID: <bfb8370e-43e4-7f72-a71f-8481eb66f6ed@linux.intel.com>
Date:   Fri, 29 Jan 2021 14:20:18 +0800
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On 1/29/2021 2:08 AM, Paul E. McKenney wrote:
> On Thu, Jan 28, 2021 at 05:09:05PM +0800, Hillf Danton wrote:
>> On Thu, 28 Jan 2021 15:52:40 +0800 Xing Zhengjun wrote:
> 
> [ . . . ]
> 
>>> I test the patch 4 times, no warning appears in the kernel log.
>>
>> Thank you so much Zhengjun!
>>
>> And the overall brain dump so far is
>>
>> 1/ before and after d5bff968ea, changing the allowed ptr at online time
>> is the key to quiesce the warning in process_one_work().
>>
>> 2/ marking pcpu before changing aptr in rebind_workers() is mandatory in
>> regards to cutting the risk of triggering such a warning.
>>
>> 3/ we canot maintain such an order without quiescing the 508 warning for
>> kworkers. And we have a couple of excuses to do so, a) the number of
>> allowed CPUs is no longer checked in is_per_cpu_kthread() instead of
>> PF_NO_SETAFFINITY, b) there is always a followup act to change the aptr
>> in order to fix the number of aCPUs.
>>
>> 4/ same order is maintained also at rescue time.
> 
> Just out of curiosity, does this test still fail on current mainline?
> 
> 							Thanx, Paul
> 
I test mainline v5.11-rc5, it has no issue. The issue is only for 
d5bff968ea which is in 
https://git.kernel.org/cgit/linux/kernel/git/paulmck/linux-rcu.git 
dev.2021.01.11b.

-- 
Zhengjun Xing