linux-kernel - Re: [PATCH 1/2] kernel/reboot.c: Add orderly

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Message-ID: <551B7C9F.5030203@linux.vnet.ibm.com>
Date:	Wed, 01 Apr 2015 10:35:35 +0530
From:	Anshuman Khandual <khandual@...ux.vnet.ibm.com>
To:	Joel Stanley <joel@....id.au>,
	Andrew Morton <akpm@...ux-foundation.org>
CC:	Rusty Russell <rusty@...tcorp.com.au>,
	linux-kernel@...r.kernel.org, fabf@...net.be,
	Jeremy Kerr <jk@...abs.org>, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH 1/2] kernel/reboot.c: Add orderly_reboot for graceful
 reboot

On 04/01/2015 08:47 AM, Joel Stanley wrote:
> Hi Andrew,
> 
> On Wed, Apr 1, 2015 at 9:09 AM, Andrew Morton <akpm@...ux-foundation.org> wrote:
>> > On Mon, 30 Mar 2015 12:45:32 +1030 Joel Stanley <joel@....id.au> wrote:
>> >
>>> >> The kernel has orderly_poweroff which allows the kernel to initiate a
>>> >> graceful shutdown of userspace, by running /sbin/poweroff. This adds
>>> >> orderly_reboot that will cause userspace to shut itself down by calling
>>> >> /sbin/reboot.
>>> >>
>>> >> This will be used for shutdown initiated by a system controller on
>>> >> platforms that do not use ACPI.
>> >
>> > gee.  There are a lot of callers of emergency_restart().  Why is the
>> > BMC reboot special, and how many of the emergency_restart() callers
>> > really be using orderly_reboot()?
> The BMC reboot is intended to be a graceful shutdown - let userspace
> do it's thing before the system goes down.
> 
> Userspace may chose to stop and perform some long, slow teardown
> before it gets around to shutting down. We don't want to move callers
> over orderly_reboot() if they're shutting the system down due to a
> critical failure, eg. printer on fire.
> 
> I had a read of the emergency_restart() callers and I didn't see any
> obvious cases for moving over to orderly_reboot().
> 
>> > We have /proc/sys/kernel/poweroff_cmd.  Should we have
>> > /proc/sys/kernel/reboot_cmd as well?  If not,
>> > kernel/reboot.c:reboot_cmd[] can be made static ;)
> I don't think we need it. I'll make reboot_cmd[] static.

Just to have parity with power off command, /proc/sys/kernel/reboot_cmd would
be nice to have.

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