All of lore.kernel.org
 help / color / mirror / Atom feed
From: Stephen Warren <swarren@wwwdotorg.org>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Stephen Warren <swarren@nvidia.com>,
	"kexec@lists.infradead.org" <kexec@lists.infradead.org>,
	Stephen Boyd <sboyd@codeaurora.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Will Deacon <will.deacon@arm.com>,
	Russell King - ARM Linux <linux@arm.linux.org.uk>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH] ARM: call disable_nonboot_cpus() from machine_shutdown()
Date: Tue, 29 Jan 2013 15:10:42 -0700	[thread overview]
Message-ID: <510848E2.50203@wwwdotorg.org> (raw)
In-Reply-To: <87obgwb5d1.fsf@xmission.com>

On 01/10/2013 11:28 PM, Eric W. Biederman wrote:
...
> I don't have any problem with generic code in the reboot path
> doing:
> if (cpu_online(0))
> 	set_cpus_allowed_ptr(current, cpumask_of(0));

It looks like that API just affects the scheduler, and not whether the
other CPUs are actually active/hot-plugged-in. At least for my use-case,
I need something that really disables the other CPUs so they aren't
executing code, hence my tendency to hot-un-plug them using
disable_nonboot_cpus(), rather than just shift task execution off them
using the code above.

I wonder if all architectures shouldn't always do the following in all
reboot/shutdown/kexec cases:

* set_cpus_allowed_ptr() to limit code execution to a single CPU.
* disable_nonboot_cpus() (or equivalent) if it's available to turn off
all the other CPUs.

The issue here would be that disable_nonboot_cpus() isn't always
available; I assume that's part of the reason that there are
arch-specific machine_xxx() hooks, so that architectures can
power-off/reset their CPUs even when hotplug isn't enabled? I wonder if
that can be refactored so that reboot/poweroff/kexec can share some
CPU-disable code with CPU hotplug?

_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec

WARNING: multiple messages have this Message-ID (diff)
From: swarren@wwwdotorg.org (Stephen Warren)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] ARM: call disable_nonboot_cpus() from machine_shutdown()
Date: Tue, 29 Jan 2013 15:10:42 -0700	[thread overview]
Message-ID: <510848E2.50203@wwwdotorg.org> (raw)
In-Reply-To: <87obgwb5d1.fsf@xmission.com>

On 01/10/2013 11:28 PM, Eric W. Biederman wrote:
...
> I don't have any problem with generic code in the reboot path
> doing:
> if (cpu_online(0))
> 	set_cpus_allowed_ptr(current, cpumask_of(0));

It looks like that API just affects the scheduler, and not whether the
other CPUs are actually active/hot-plugged-in. At least for my use-case,
I need something that really disables the other CPUs so they aren't
executing code, hence my tendency to hot-un-plug them using
disable_nonboot_cpus(), rather than just shift task execution off them
using the code above.

I wonder if all architectures shouldn't always do the following in all
reboot/shutdown/kexec cases:

* set_cpus_allowed_ptr() to limit code execution to a single CPU.
* disable_nonboot_cpus() (or equivalent) if it's available to turn off
all the other CPUs.

The issue here would be that disable_nonboot_cpus() isn't always
available; I assume that's part of the reason that there are
arch-specific machine_xxx() hooks, so that architectures can
power-off/reset their CPUs even when hotplug isn't enabled? I wonder if
that can be refactored so that reboot/poweroff/kexec can share some
CPU-disable code with CPU hotplug?

WARNING: multiple messages have this Message-ID (diff)
From: Stephen Warren <swarren@wwwdotorg.org>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Stephen Warren <swarren@nvidia.com>,
	Stephen Boyd <sboyd@codeaurora.org>,
	Will Deacon <will.deacon@arm.com>,
	Russell King - ARM Linux <linux@arm.linux.org.uk>,
	"kexec@lists.infradead.org" <kexec@lists.infradead.org>,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] ARM: call disable_nonboot_cpus() from machine_shutdown()
Date: Tue, 29 Jan 2013 15:10:42 -0700	[thread overview]
Message-ID: <510848E2.50203@wwwdotorg.org> (raw)
In-Reply-To: <87obgwb5d1.fsf@xmission.com>

On 01/10/2013 11:28 PM, Eric W. Biederman wrote:
...
> I don't have any problem with generic code in the reboot path
> doing:
> if (cpu_online(0))
> 	set_cpus_allowed_ptr(current, cpumask_of(0));

It looks like that API just affects the scheduler, and not whether the
other CPUs are actually active/hot-plugged-in. At least for my use-case,
I need something that really disables the other CPUs so they aren't
executing code, hence my tendency to hot-un-plug them using
disable_nonboot_cpus(), rather than just shift task execution off them
using the code above.

I wonder if all architectures shouldn't always do the following in all
reboot/shutdown/kexec cases:

* set_cpus_allowed_ptr() to limit code execution to a single CPU.
* disable_nonboot_cpus() (or equivalent) if it's available to turn off
all the other CPUs.

The issue here would be that disable_nonboot_cpus() isn't always
available; I assume that's part of the reason that there are
arch-specific machine_xxx() hooks, so that architectures can
power-off/reset their CPUs even when hotplug isn't enabled? I wonder if
that can be refactored so that reboot/poweroff/kexec can share some
CPU-disable code with CPU hotplug?

  reply	other threads:[~2013-01-29 22:10 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-01-02 21:07 [PATCH] ARM: call disable_nonboot_cpus() from machine_shutdown() Stephen Warren
2013-01-02 21:07 ` Stephen Warren
2013-01-02 21:52 ` Russell King - ARM Linux
2013-01-02 21:52   ` Russell King - ARM Linux
2013-01-02 23:59 ` Stephen Boyd
2013-01-02 23:59   ` Stephen Boyd
2013-01-03 12:02   ` Will Deacon
2013-01-03 12:02     ` Will Deacon
2013-01-03 12:21     ` Russell King - ARM Linux
2013-01-03 12:21       ` Russell King - ARM Linux
2013-01-03 18:08       ` Jason Gunthorpe
2013-01-03 18:08         ` Jason Gunthorpe
2013-01-03 20:26       ` Stephen Warren
2013-01-03 20:26         ` Stephen Warren
2013-01-06 16:22         ` Will Deacon
2013-01-06 16:22           ` Will Deacon
2013-01-06 16:40           ` Russell King - ARM Linux
2013-01-06 16:40             ` Russell King - ARM Linux
2013-01-07  1:53             ` Eric W. Biederman
2013-01-07  1:53               ` Eric W. Biederman
2013-01-07 14:25               ` Will Deacon
2013-01-07 14:25                 ` Will Deacon
2013-01-07 14:48               ` Russell King - ARM Linux
2013-01-07 14:48                 ` Russell King - ARM Linux
2013-01-11  5:59                 ` Eric W. Biederman
2013-01-11  5:59                   ` Eric W. Biederman
2013-01-11 10:04                   ` Russell King - ARM Linux
2013-01-11 10:04                     ` Russell King - ARM Linux
2013-01-29 22:01                   ` Stephen Warren
2013-01-29 22:01                     ` Stephen Warren
2013-01-29 22:01                     ` Stephen Warren
2013-01-09  0:06               ` Stephen Warren
2013-01-09  0:06                 ` Stephen Warren
2013-01-11  6:28                 ` Eric W. Biederman
2013-01-11  6:28                   ` Eric W. Biederman
2013-01-29 22:10                   ` Stephen Warren [this message]
2013-01-29 22:10                     ` Stephen Warren
2013-01-29 22:10                     ` Stephen Warren
2013-01-03 12:03 ` Will Deacon
2013-01-03 12:03   ` Will Deacon

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=510848E2.50203@wwwdotorg.org \
    --to=swarren@wwwdotorg.org \
    --cc=ebiederm@xmission.com \
    --cc=kexec@lists.infradead.org \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux@arm.linux.org.uk \
    --cc=sboyd@codeaurora.org \
    --cc=swarren@nvidia.com \
    --cc=will.deacon@arm.com \
    /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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.