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From: Meng Xu <xumengpanda@gmail.com>
To: Dario Faggioli <dario.faggioli@citrix.com>
Cc: "xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
	Dagaen Golomb <dgolomb@seas.upenn.edu>,
	George Dunlap <george.dunlap@citrix.com>,
	Jan Beulich <JBeulich@suse.com>,
	Tianyang Chen <tiche@seas.upenn.edu>
Subject: Re: [PATCH v11]xen: sched: convert RTDS from time to event driven model
Date: Fri, 18 Mar 2016 10:23:08 -0400	[thread overview]
Message-ID: <CAENZ-+ko9WwMp9s86pBg_YjFpFTkab-bHd=dPpRsuj56MPO1xQ@mail.gmail.com> (raw)
In-Reply-To: <1458293001.15374.87.camel@citrix.com>

>> > I tried to create a cpupool and then migrate a VM to the new
>> > cpupool;
>>
> BTW, Meng:
>
> (XEN)    [<ffff82d08012e182>] schedule_cpu_switch+0x250/0x28a
> (XEN)    [<ffff82d080101b49>] cpupool.c#cpupool_assign_cpu_locked+0x31/0x11f
>
> I think you mean "and then move a CPU from a cpupool to another". Or
> perhaps what you said is what your script does, and you weren't sure at
> what stage it explodes.
>
> Well, let me tell you: it's when you move a CPU between pools that have
> schedulers that remaps the scheduler locks (such as Credit2-->RTDS and
> vice versa).

Thanks Dario for the explanation!
Yes, I looked into the cpu_switch things before and found the bug is
triggered by the lock remapping.

>
>> > However, the system triggers the bug as below. I guess this is some
>> > kind of bug that are known to us,  and Dario had some uncommitted
>> > patch to fix it, IIRC?
>> In the context of this patch the most relevant question is: Is this
>> an issue with the patch, or one that existed already before?
>>
> Exactly!
>
> And the answer is:
>  - it's pre-existing
>  - it's an even bigger issue than that ASSERT triggering (i.e., there
>    are potential races even when things works)

Ah-ha, I didn't know this before. :-)

>  - I'm taking care of it.

Thank you so much! I'm looking forward to it. :-D

Thanks and Best Regards,

Meng

-----------
Meng Xu
PhD Student in Computer and Information Science
University of Pennsylvania
http://www.cis.upenn.edu/~mengxu/

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  reply	other threads:[~2016-03-18 14:23 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-03-17 16:06 Tianyang Chen
2016-03-17 18:27 ` Dario Faggioli
2016-03-17 20:12   ` Chen, Tianyang
2016-03-18  1:45     ` Meng Xu
2016-03-18  4:09 ` Meng Xu
2016-03-18  7:45   ` Jan Beulich
2016-03-18  9:23     ` Dario Faggioli
2016-03-18 14:23       ` Meng Xu [this message]
2016-03-18 14:19     ` Meng Xu
2016-03-18  9:24   ` Dario Faggioli
2016-03-18 14:25 ` Meng Xu

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