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
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