linux-kernel - Re: [PATCH] efi/capsule: Make efi_capsule

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Message-ID: <20160504093031.GA4074@pd.tnic>
Date:	Wed, 4 May 2016 11:30:31 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Matt Fleming <matt@...eblueprint.co.uk>
Cc:	linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	Kweh Hock Leong <hock.leong.kweh@...el.com>,
	Bryan O'Donoghue <pure.logic@...us-software.ie>,
	joeyli <jlee@...e.com>
Subject: Re: [PATCH] efi/capsule: Make efi_capsule_pending() lockless

On Tue, May 03, 2016 at 03:12:01PM +0100, Matt Fleming wrote:
> We can find ourselves in the reboot code even if the admin has not
> executed the reboot command. The trace above shows we entered because
> the kernel panic()'d and it was booted with panic=-1.

I knew you were gonna say something like that...

> Right. You could find yourself in this situation if you're in the
> middle of a capsule update and the box panics and reboots. Like you
> said, there's really not much you can do there to ensure the update
> completes. Your best option is to just not block and hang the machine.

Hmmm, so panic() does bust_spinlocks() and efi_capsule_pending() could
look at oops_in_progress which is set by bust_spinlocks() and that would
probably solve the panic case but maybe the normal reboot case would
still hang...

> Note that in the panic() -> emergency_restart() case the reboot
> notifiers are not called at all.

And then there's that.

-- 
Regards/Gruss,
    Boris.

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