Re: 3.17-rc6: bcache_gc: BUG: soft lockup - CPU#2 stuck for 23s!

Eric Wheeler
2014-11-24T18:52:42Z

>>> Before the patch goes upstream I need it tested so I know if it fixes
>>> the actual issue or not.
>>
>> We have been using the rcu_sched patch and the cond_resched patch together
>> (both attached) since November 3rd on 3.17.2 without any bcache
>> backtraces. bcache is running in writeback mode. The server is
>> predominantly write-only with relatively few reads.
>
> Is the rcu_sched patch supposed to help the same or a totally different
> problem? Means: should I also apply it, rebuild the module and reboot
> (resetting the test time to zero :-)

The second backtrace mentioned on this link is the issue that I believe is
fixed with the rcu_sched patch:

https://www.mail-archive.com/linux-bcache@vger.kernel.org/msg02623.html

The error starts with a message like "INFO: rcu_sched self-detected stall
on CPU"

-Eric

> I had the "deadly" soft lockup once per week since updating to
> 3.16/3.17, so I can only tell if it might help in two weeks earliest.
>
>> To sum up, the attached two patches (plus the for-jens pull) have fixed all
>> of our bcache problems since 3.14.y. These patches on 3.17.2 seem quite stable.
>
> That's good to hear :-)
>
> Best regards,
>
> Stefan
> --
> Stefan Seyfried
> Linux Consultant & Developer -- GPG Key: 0x731B665B
>
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