From: Juergen Gross <jgross@suse.com>
To: Dario Faggioli <dario.faggioli@citrix.com>
Cc: George Dunlap <george.dunlap@eu.citrix.com>,
xen-devel@lists.xenproject.org
Subject: Re: [PATCH v2 1/2] xen: sched: reorganize cpu_disable_scheduler()
Date: Mon, 20 Jul 2015 14:06:13 +0200 [thread overview]
Message-ID: <55ACE435.6040308@suse.com> (raw)
In-Reply-To: <1437393585.5036.8.camel@citrix.com>
On 07/20/2015 01:59 PM, Dario Faggioli wrote:
> On Mon, 2015-07-20 at 13:41 +0200, Juergen Gross wrote:
>> On 07/17/2015 03:35 PM, Dario Faggioli wrote:
>
>>> @@ -644,25 +673,66 @@ int cpu_disable_scheduler(unsigned int cpu)
>>> cpumask_setall(v->cpu_hard_affinity);
>>> }
>>>
>>> - if ( v->processor == cpu )
>>> + if ( v->processor != cpu )
>>> {
>>> - set_bit(_VPF_migrating, &v->pause_flags);
>>> + /* This vcpu is not on cpu, so we can move on. */
>>> vcpu_schedule_unlock_irqrestore(lock, flags, v);
>>> - vcpu_sleep_nosync(v);
>>> - vcpu_migrate(v);
>>> + continue;
>>> + }
>>> +
>>> + /* If it is on cpu, we must send it away. */
>>> + if ( unlikely(system_state == SYS_STATE_suspend) )
>>> + {
>>> + /*
>>> + * If we are doing a shutdown/suspend, it is not necessary to
>>> + * ask the scheduler to chime in. In fact:
>>> + * * there is no reason for it: the end result we are after
>>> + * is just 'all the vcpus on the boot pcpu, and no vcpu
>>> + * anywhere else', so let's just go for it;
>>> + * * it's wrong, for cpupools with only non-boot pcpus, as
>>> + * the scheduler would always fail to send the vcpus away
>>> + * from the last online (non boot) pcpu!
>>> + *
>>> + * Therefore, in the shutdown/suspend case, we just pick up
>>> + * one (still) online pcpu. Note that, at this stage, all
>>> + * domains (including dom0) have been paused already, so we
>>> + * do not expect any vcpu activity at all.
>>> + */
>>> + cpumask_andnot(&online_affinity, &cpu_online_map,
>>> + cpumask_of(cpu));
>>> + BUG_ON(cpumask_empty(&online_affinity));
>>> + /*
>>> + * As boot cpu is, usually, pcpu #0, using cpumask_first()
>>> + * will make us converge quicker.
>>> + */
>>> + new_cpu = cpumask_first(&online_affinity);
>>> + vcpu_move_nosched(v, new_cpu);
>>
>> Shouldn't there be a vcpu_schedule_unlock_irqrestore() ?
>>
> I'm sure I put one there, as I was sure that it was there the last time
> I inspected the patch before hitting send.
>
> But I see that it's not there now, so I must have messed up when
> formatting the patch, or something like that. :-(
>
> It's really really weird, as I forgot it during development, and then
> the system was hanging, and then I added it, and that's why I'm sure I
> did have it in place... but perhaps I fat fingered some stgit command
> which made it disappear.
Or you forgot stg refresh? I just managed to do so. :-(
Juergen
next prev parent reply other threads:[~2015-07-20 12:06 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-17 13:35 [PATCH v2 0/2] xen: sched/cpupool: more fixing of (corner?) cases Dario Faggioli
2015-07-17 13:35 ` [PATCH v2 1/2] xen: sched: reorganize cpu_disable_scheduler() Dario Faggioli
2015-07-20 11:41 ` Juergen Gross
2015-07-20 11:59 ` Dario Faggioli
2015-07-20 12:06 ` Juergen Gross [this message]
2015-07-17 13:36 ` [PATCH v2 2/2] xen: sched/cpupool: properly update affinity when removing a cpu from a cpupool Dario Faggioli
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=55ACE435.6040308@suse.com \
--to=jgross@suse.com \
--cc=dario.faggioli@citrix.com \
--cc=george.dunlap@eu.citrix.com \
--cc=xen-devel@lists.xenproject.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).