From: "Rafael J. Wysocki" <rjw@sisk.pl>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>,
paulmck@linux.vnet.ibm.com, Ingo Molnar <mingo@elte.hu>,
"Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>,
paul@paulmenage.org, tj@kernel.org, frank.rowand@am.sony.com,
pjt@google.com, tglx@linutronix.de, lizf@cn.fujitsu.com,
prashanth@linux.vnet.ibm.com, vatsa@linux.vnet.ibm.com,
linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
"akpm@linux-foundation.org" <akpm@linux-foundation.org>
Subject: Re: [PATCH 0/4] CPU hotplug, cpusets: Fix CPU online handling related to cpusets
Date: Fri, 10 Feb 2012 23:39:02 +0100 [thread overview]
Message-ID: <201202102339.02702.rjw@sisk.pl> (raw)
In-Reply-To: <Pine.LNX.4.44L0.1202101647440.1179-100000@iolanthe.rowland.org>
On Friday, February 10, 2012, Alan Stern wrote:
> On Fri, 10 Feb 2012, Peter Zijlstra wrote:
>
> > Now the whole problem here seems to be that suspend uses cpu-hotplug to
> > reduce the machine to UP -- I've no clue why it does that but I can
> > imagine its because the BIOS calls only work on CPU0 and/or the resume
> > only wakes CPU0 so you have to bootstrap the SMP thing again..
Yes, that's the main problem.
> > Some suspend person wanna clarify? Rafael?
>
> If I understand correctly, ACPI requires that only CPU0 be running when
> the system is suspended (i.e., your guess is right). Of course, this
> doesn't apply to non-ACPI systems, but it's easiest to do the same
> thing everywhere.
That's correct. Plus we have some code in the kernel (syscore_ops in
general) that assumes to be executed on one CPU with interrupts off.
Plus I'm not sure how the ACPI low-level suspend is going to behave if it's
not executed on the boot CPU.
> > Anyway, the whole suspend case is magic anyway since all tasks will have
> > been frozen, so we could simply leave all of cpuset alone and ignore the
> > hotplug notifier on CPU_TASKS_FROZEN callbacks, hmm?
>
> I don't see why not. Presumably no CPUs will be added or removed while
> the system is asleep.
ACPI explicitly forbids that level of hardware reconfiguration in a sleep
state (even in S4), AFAICS. Still, people may try to do that ...
Thanks,
Rafael
next prev parent reply other threads:[~2012-02-10 22:35 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-07 18:55 [PATCH 0/4] CPU hotplug, cpusets: Fix CPU online handling related to cpusets Srivatsa S. Bhat
2012-02-07 18:56 ` [PATCH 1/4] CPU hotplug, cpuset: Maintain a copy of the cpus_allowed mask before CPU hotplug Srivatsa S. Bhat
2012-02-07 18:56 ` [PATCH 2/4] cpuset: Split up update_cpumask() so that its functionality can be reused Srivatsa S. Bhat
2012-02-07 18:57 ` [PATCH 3/4] cpuset: Add function to introduce CPUs to cpusets during CPU online Srivatsa S. Bhat
2012-02-07 18:57 ` [PATCH 4/4] CPU hotplug, cpusets: Differentiate the CPU online and CPU offline callbacks Srivatsa S. Bhat
2012-02-08 3:22 ` [PATCH 0/4] CPU hotplug, cpusets: Fix CPU online handling related to cpusets Peter Zijlstra
2012-02-08 6:33 ` Srivatsa S. Bhat
2012-02-09 7:57 ` Ingo Molnar
2012-02-09 8:42 ` Srivatsa S. Bhat
2012-02-09 15:11 ` Ingo Molnar
2012-02-10 15:52 ` Peter Zijlstra
2012-02-10 16:53 ` Paul E. McKenney
2012-02-10 17:34 ` Peter Zijlstra
2012-02-10 21:51 ` Alan Stern
2012-02-10 22:39 ` Rafael J. Wysocki [this message]
2012-02-11 2:07 ` Peter Zijlstra
2012-02-11 4:26 ` Srivatsa S. Bhat
2012-02-13 17:47 ` Srivatsa S. Bhat
2012-02-17 12:15 ` Srivatsa S. Bhat
2012-02-20 12:49 ` Peter Zijlstra
2012-02-20 12:59 ` Srivatsa S. Bhat
2012-02-23 9:57 ` Srivatsa S. Bhat
2012-02-24 23:24 ` Rafael J. Wysocki
2012-02-27 10:18 ` Peter Zijlstra
2012-02-27 12:09 ` [tip:sched/urgent] CPU hotplug, cpusets, suspend: Don' t touch cpusets during suspend/resume tip-bot for Srivatsa S. Bhat
2012-02-11 16:00 ` [PATCH 0/4] CPU hotplug, cpusets: Fix CPU online handling related to cpusets Paul E. McKenney
2012-02-13 17:47 ` Srivatsa S. Bhat
2012-02-13 20:39 ` Paul E. McKenney
2012-02-13 20:49 ` Srivatsa S. Bhat
2012-02-11 13:39 ` Ingo Molnar
2012-02-10 15:53 ` Peter Zijlstra
2012-02-09 16:43 ` Peter Zijlstra
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