linux-kernel - Re: [PATCH] PM/reboot: call syscore_shutdown() after disable_nonboot

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Date:	Mon, 8 Apr 2013 10:51:45 +0800
From:	chenhc@...ote.com
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	"Greg KH" <gregkh@...uxfoundation.org>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	"Fuxin Zhang" <zhangfx@...ote.com>, stable@...r.kernel.org
Subject: Re: [PATCH] PM/reboot: call syscore_shutdown() after
 disable_nonboot_cpus()

> On Sunday, April 07, 2013 08:29:32 AM Greg KH wrote:
>> On Sun, Apr 07, 2013 at 10:46:00AM +0200, Rafael J. Wysocki wrote:
>> > On Sunday, April 07, 2013 10:14:14 AM Huacai Chen wrote:
>> > > As commit 40dc166c (PM / Core: Introduce struct syscore_ops for core
>> > > subsystems PM) say, syscore_ops operations should be carried with
>> one
>> > > CPU on-line and interrupts disabled. However, after commit f96972f2d
>> > > (kernel/sys.c: call disable_nonboot_cpus() in kernel_restart()),
>> > > syscore_shutdown() is called before disable_nonboot_cpus(), so break
>> > > the rules. We have a MIPS machine with a 8259A PIC, and there is an
>> > > external timer (HPET) linked at 8259A. Since 8259A has been shutdown
>> > > too early (by syscore_shutdown()), disable_nonboot_cpus() runs
>> without
>> > > timer interrupt, so it hangs and reboot fails. This patch call
>> > > syscore_shutdown() a little later (after disable_nonboot_cpus()) to
>> > > avoid reboot failure, this is the same way as poweroff does.
>> > >
>> > > BTW, add disable_nonboot_cpus() in kernel_halt() for consistency.
>> > >
>> > > Signed-off-by: Huacai Chen <chenhc@...ote.com>
>> > > Cc: <stable@...r.kernel.org>
>> >
>> > While I agree with the changes, I'm not sure if I'm the right
>> maintainer,
>> > as this isn't really PM code.
>> >
>> > Andrew, should I take this?
>>
>> Andrew is on vacation for a few weeks, so you might need to take this
>> through your tree.
>
> OK
>
> But, it looks like we should actually disable interrupts on the remaining
> CPU after we've called disable_nonboot_cpus() so that the
> syscore_shutdown()
> assumptions are satisfied which the patch doesn't do.
>
> Chen (I apologize if that's not the right part of your full name to use
> here),
> do you think that's not necessary and if so, then for what reason?

Reboot and poweroff are both OK after I move syscore_shutdown(), I also don't
know whether we should disable interrupts. Since you are the author of
commit 40dc166c (PM / Core: Introduce struct syscore_ops for core subsystems
 PM), please tell me why syscore_shutdown() need interrupt disabled? (I just
know that syscore_shutdown() will cause disable_nonboot_cpus() hang)

BTW, Chen is my last name and you needn't worry about this.

>
> Rafael
>
>
> --
> I speak only for myself.
> Rafael J. Wysocki, Intel Open Source Technology Center.
>


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