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From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Dario Faggioli <dario.faggioli@citrix.com>,
	George Dunlap <george.dunlap@citrix.com>,
	xen-devel@lists.xenproject.org
Cc: Anshul Makkar <anshul.makkar@citrix.com>,
	Meng Xu <mengxu@cis.upenn.edu>, Jan Beulich <jbeulich@suse.com>
Subject: Re: [PATCH 2/3] xen: Have schedulers revise initial placement
Date: Mon, 18 Jul 2016 19:10:33 +0100	[thread overview]
Message-ID: <6bfba010-3712-8d43-f866-38b3bfc1444f@citrix.com> (raw)
In-Reply-To: <1468678323.13039.132.camel@citrix.com>

On 16/07/16 15:12, Dario Faggioli wrote:
> On Fri, 2016-07-15 at 19:07 +0100, Andrew Cooper wrote:
>
>> None of the scheduler-accounting functions should be disabling
>> interrupts.
>>
> They don't. But you can't keep irq disabled for some operations and
> enabled for others, on the same lock (because of the irq-safety
> spinlock checks/enforcement).
>
> So you have to always keep IRQ enabled, for all scheduling operations,
> which is ok for _almost_ all of them, with the only exception of the
> wakeup of a vcpu.

I know that it is all or nothing.  What specific action about waking a
vcpu requires holding a lock?

If it is simply re-queueing the vcpu onto the runable queue, there are a
number of lockless queuing algorithms which can be used.

~Andrew

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  reply	other threads:[~2016-07-18 18:10 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-07-15 18:02 [PATCH 1/3] xen: Some code motion to avoid having to do forward-declaration George Dunlap
2016-07-15 18:02 ` [PATCH 2/3] xen: Have schedulers revise initial placement George Dunlap
2016-07-15 18:07   ` Andrew Cooper
2016-07-16 14:12     ` Dario Faggioli
2016-07-18 18:10       ` Andrew Cooper [this message]
2016-07-18 18:55         ` Dario Faggioli
2016-07-18 21:36           ` Andrew Cooper
2016-07-19  7:14             ` Dario Faggioli
2016-07-18 10:28   ` Dario Faggioli
2016-07-25 11:17     ` George Dunlap
2016-07-25 14:36       ` Meng Xu
2016-07-26  9:17       ` Dario Faggioli
2016-07-25 14:35   ` Meng Xu
2016-08-01 10:40   ` Jan Beulich
2016-08-01 12:32     ` Dario Faggioli
2016-08-05 13:24       ` Jan Beulich
2016-08-05 14:09         ` Dario Faggioli
2016-08-05 14:44           ` Jan Beulich
2016-08-11 14:59         ` Dario Faggioli
2016-08-11 15:51           ` Andrew Cooper
2016-08-11 23:35             ` Dario Faggioli
2016-08-12  1:59         ` dependences for backporting to 4.6 [was: Re: [PATCH 2/3] xen: Have schedulers revise initial placement] Dario Faggioli
2016-08-12 13:53           ` Jan Beulich
2016-08-16 10:21             ` Dario Faggioli
2016-08-16 11:21               ` Jan Beulich
2016-08-12  8:58         ` dependences for backporting to 4.5 " Dario Faggioli
2016-07-15 18:02 ` [PATCH 3/3] xen: Remove buggy initial placement algorithm George Dunlap
2016-07-15 18:10   ` Andrew Cooper
2016-07-16 13:55   ` Dario Faggioli
2016-07-18 10:03     ` George Dunlap
2016-07-16 15:48 ` [PATCH 1/3] xen: Some code motion to avoid having to do forward-declaration Meng Xu
2016-07-18  9:58 ` Dario Faggioli
2016-07-18 10:06   ` George Dunlap

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