Re: [PATCH] cpupool: fix ASSERT( c != old_pool )

From: Juergen Gross <jgross@suse.com>
To: Jan Beulich <JBeulich@suse.com>,
	"FionaLi-oc <fionali-oc@zhaoxin.com>" <fionali-oc@zhaoxin.com>
Cc: xen-devel <xen-devel@lists.xenproject.org>,
	cobechen@zhaoxin.com, Dario Faggioli <dfaggioli@suse.com>
Subject: Re: [PATCH] cpupool: fix ASSERT( c != old_pool )
Date: Mon, 8 Apr 2019 12:25:06 +0200	[thread overview]
Message-ID: <11f0f156-4313-00c4-0355-0fdb82db70cb@suse.com> (raw)

On 08/04/2019 11:26, Jan Beulich wrote:
>>>> On 08.04.19 at 07:09, <jgross@suse.com> wrote:
>> On 08/04/2019 04:40, FionaLi-oc wrote:
>>> Assigning cpu to cpupool needn't to switch cpu scheduler when
>>> system state is resume, otherwise it will cause ASSERT in
>>> schedule_cpu_switch().
>>
>> I don't think this patch is needed on current staging tree. Commit
>> 6870ea9d1fad6fbe27 changed resume handling leading to
>> cpupool_assign_cpu_locked() being no longer called when resuming.
> 
> But is it something worthwhile to put onto stable trees (with the
> one missing blank added)?

I don't think it is always correct.

While avoiding the ASSERT() triggering it won't switch back the
scheduler from the default one at resume, which was activated when
suspending the machine.

So for older Xen versions we'd need to know which ASSERT() was
triggering and why that did happen, or we could backport my series
removing really the need for calling schedule_cpu_switch().

Juergen

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