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From: Dario Faggioli <dario.faggioli@citrix.com>
To: Julien Grall <julien.grall@arm.com>,
	Ivan Pavic <ivan.pavic2@fer.hr>,
	"xen-devel@lists.xen.org" <xen-devel@lists.xen.org>,
	Stefano Stabellini <sstabellini@kernel.org>
Subject: Re: Possible bug on ARM with irq passthrough
Date: Wed, 5 Jul 2017 15:42:02 +0200	[thread overview]
Message-ID: <1499262122.7486.14.camel@citrix.com> (raw)
In-Reply-To: <78bd7ab8-23bf-637b-6ec8-ea777e3623ee@arm.com>


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On Wed, 2017-07-05 at 13:55 +0100, Julien Grall wrote:
> 
> If you got a message in the former, but not the latter. Then you hit
> the 
> bug described in my previous e-mail.
> 
> This would happen if some of the pCPUs are idle states (using wfi).r.
> The main difference between credit1 and credit2 (I am not sure for
> RTDS) 
> is there are IPI traffic with credit1 on idle pCPU because of the
> ticker.
> 
Exactly,

It's a bug in RCU, which happens to be exposed (or, at least, it turns
out to be this severe) only by certain schedulers, and only on ARM.

I think it makes sense that this is visible with RTDS as well, because
it also does not have a periodic timer.

Dario
-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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  reply	other threads:[~2017-07-05 13:42 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-07-04 20:20 Possible bug on ARM with irq passthrough Ivan Pavić2
2017-07-05 11:27 ` Julien Grall
2017-07-05 12:36   ` Ivan Pavic
2017-07-05 12:55     ` Julien Grall
2017-07-05 13:42       ` Dario Faggioli [this message]
2017-07-05 13:50       ` Ivan Pavic
2017-07-07 16:19         ` Julien Grall
2017-07-08  7:25           ` Dario Faggioli
2017-07-27 11:27             ` Dario Faggioli
2017-07-05 13:39   ` Dario Faggioli

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