Re: null scheduler bug

From: Dario Faggioli <dfaggioli@suse.com>
To: Milan Boberic <milanboberic94@gmail.com>
Cc: xen-devel@lists.xenproject.org, stefano@stabellini.net
Subject: Re: null scheduler bug
Date: Thu, 13 Sep 2018 19:39:02 +0200	[thread overview]
Message-ID: <529d38d04b140d90d33e424a064d401cf06f14cf.camel@suse.com> (raw)
In-Reply-To: <CADJ6SV2wis2kOz9j4OGTzRLd+2O2f_SuxktFWRq2A_tbng_3Ug@mail.gmail.com>

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On Thu, 2018-09-13 at 17:18 +0200, Milan Boberic wrote:
> Commits are there and I will definitely continue with 4.10 version.
> But it didn't solve my problem entirely.
> 
> I create my bare-metal application (with xl create) and destroy it
> with xl destroy (it disappears from xl list) and when I try to create
> it again same error pops but if I immediately run xl create command
> again it creates it without error.
> If I run xl create twice fast sometimes bare-metal application isn't
> in any state (it should be in "running" state).
> If I wait some time (approximately between 30 and 90 seconds) after
> destruction of that bm app and then run xl create it will create it
> without error.
> 
Ok, thanks for trying and reporting back.

If possible, help me understand things a bit better.

So, can you confirm that the situation _actually_improves_ with Xen
4.10 ? 

Basically, as far as I've understood things, with Xen 4.9, you destroy
a guest, and you can _never_ re-create it, not even after 30 seconds,
90 seconds, 2 minutes, 1 hour, ecc. Is that correct?

With Xen 4.10, it may still fail, if you try to re-create it within ~30
to 90 seconds, but after that, it works. Is that also correct?

I need to know this, because I want to understand if the issue is, at
least partially, cured by the RCU fixes, although having to wait 30
seconds is definitely not what I was expecting (i.e., there might be
something else).

Another question, in case I manage to produce a debug patch, are you ok
to put it in your source tree, build with it, and tell us what you see?

Thanks again and Regards,
Dario
-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Software Engineer @ SUSE https://www.suse.com/

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