From: "Jan Beulich" <JBeulich@suse.com>
To: David Vrabel <david.vrabel@citrix.com>
Cc: AndrewCooper <andrew.cooper3@citrix.com>,
Keir Fraser <keir@xen.org>,
xen-devel@lists.xenproject.org
Subject: Re: [PATCH 3/4] x86/nmi: wait for all CPUs in check_nmi_watchdog()
Date: Wed, 14 May 2014 15:33:49 +0100 [thread overview]
Message-ID: <53739AED020000780001242C@mail.emea.novell.com> (raw)
In-Reply-To: <5373791A.4070506@citrix.com>
>>> On 14.05.14 at 16:09, <david.vrabel@citrix.com> wrote:
> x86/nmi: wait for all CPUs in check_nmi_watchdog()
>
> The counting of a CPUs NMIs in check_nmi_watchdog() is only reliable
> if all CPUs have been spinning for 5 or more ticks. Whilst its highly
> implausible that this won't happen in practise, explicitly wait so it's
> clear that this is required.
The thing is that I actually consider the early continuation to be
desirable - there's no need for the BP to actually wait for the APs
to finish their wait loop, as long as they progressed far enough
into it. If you added a flag telling the others to bail as soon as the
master exited its waiting, that would look more acceptable to me.
Agreed we're not talking about big time differences here, but
we shouldn't be making booting slower than it needs to be. Btw.,
did you check how modern Linux deals with the same issue (last I
looked was many releases ago)?
Jan
next prev parent reply other threads:[~2014-05-14 14:33 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-14 12:58 [PATCH 0/4] x86/nmi: improve NMI watchdog test David Vrabel
2014-05-14 12:58 ` [PATCH 1/4] x86/nmi: remove spurious local_irq_enable from check_nmi_watchdog() David Vrabel
2014-05-14 13:25 ` Jan Beulich
2014-05-14 13:31 ` David Vrabel
2014-05-14 13:53 ` Jan Beulich
2014-05-15 11:40 ` Tim Deegan
2014-05-14 12:58 ` [PATCH 2/4] x86/nmi: enable local irqs in wait_for_nmis() David Vrabel
2014-05-14 13:57 ` Jan Beulich
2014-05-14 14:38 ` David Vrabel
2014-05-14 14:45 ` Jan Beulich
2014-05-15 11:55 ` Tim Deegan
2014-05-14 12:58 ` [PATCH 3/4] x86/nmi: wait for all CPUs in check_nmi_watchdog() David Vrabel
2014-05-14 13:59 ` Jan Beulich
2014-05-14 14:09 ` David Vrabel
2014-05-14 14:33 ` Jan Beulich [this message]
2014-05-14 14:09 ` Andrew Cooper
2014-05-15 11:47 ` Tim Deegan
2014-05-14 12:58 ` [PATCH 4/4] x86/nmi: be less verbose when testing the NMI watchdog David Vrabel
2014-05-15 11:48 ` Tim Deegan
2014-05-14 13:03 ` [PATCH 0/4] x86/nmi: improve NMI watchdog test Andrew Cooper
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