Re: [PATCH v2 03/13] firmware: google: Test spinlock on panic path to avoid lockups - Greg Kroah-Hartman

From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: "Guilherme G. Piccoli" <gpiccoli@igalia.com>
Cc: Evan Green <evgreen@chromium.org>,
	linux-efi@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
	Ard Biesheuvel <ardb@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	bhe@redhat.com, Petr Mladek <pmladek@suse.com>,
	kexec@lists.infradead.org, linux-hyperv@vger.kernel.org,
	netdev@vger.kernel.org, x86@kernel.org, kernel-dev@igalia.com,
	kernel@gpiccoli.net, halves@canonical.com, fabiomirmar@gmail.com,
	alejandro.j.jimenez@oracle.com,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Arnd Bergmann <arnd@arndb.de>, Borislav Petkov <bp@alien8.de>,
	Jonathan Corbet <corbet@lwn.net>,
	d.hatayama@jp.fujitsu.com, dave.hansen@linux.intel.com,
	dyoung@redhat.com, feng.tang@intel.com, mikelley@microsoft.com,
	hidehiro.kawai.ez@hitachi.com, jgross@suse.com,
	john.ogness@linutronix.de, Kees Cook <keescook@chromium.org>,
	luto@kernel.org, mhiramat@kernel.org, mingo@redhat.com,
	paulmck@kernel.org, peterz@infradead.org, rostedt@goodmis.org,
	senozhatsky@chromium.org, Alan Stern <stern@rowland.harvard.edu>,
	Thomas Gleixner <tglx@linutronix.de>,
	vgoyal@redhat.com, vkuznets@redhat.com,
	Will Deacon <will@kernel.org>, David Gow <davidgow@google.com>,
	Julius Werner <jwerner@chromium.org>
Subject: Re: [PATCH v2 03/13] firmware: google: Test spinlock on panic path to avoid lockups
Date: Mon, 8 Aug 2022 17:26:43 +0200	[thread overview]
Message-ID: <YvErMyM8FNjeDeiW@kroah.com> (raw)
In-Reply-To: <019ae735-3d69-cb4e-c003-b83cc8cd76f8@igalia.com>

On Mon, Aug 08, 2022 at 12:14:30PM -0300, Guilherme G. Piccoli wrote:
> On 08/08/2022 02:07, Evan Green wrote:
> > On Tue, Jul 19, 2022 at 12:55 PM Guilherme G. Piccoli
> > <gpiccoli@igalia.com> wrote:
> >>
> >> Currently the gsmi driver registers a panic notifier as well as
> >> reboot and die notifiers. The callbacks registered are called in
> >> atomic and very limited context - for instance, panic disables
> >> preemption and local IRQs, also all secondary CPUs (not executing
> >> the panic path) are shutdown.
> >>
> >> With that said, taking a spinlock in this scenario is a dangerous
> >> invitation for lockup scenarios. So, fix that by checking if the
> >> spinlock is free to acquire in the panic notifier callback - if not,
> >> bail-out and avoid a potential hang.
> >>
> >> Fixes: 74c5b31c6618 ("driver: Google EFI SMI")
> >> Cc: Ard Biesheuvel <ardb@kernel.org>
> >> Cc: David Gow <davidgow@google.com>
> >> Cc: Evan Green <evgreen@chromium.org>
> >> Cc: Julius Werner <jwerner@chromium.org>
> >> Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com>
> > 
> > Reviewed-by: Evan Green <evgreen@chromium.org>
> 
> Thanks a bunch Evan!
> 
> Ard / Greg, do you think you could get this patch through your -next (or
> -fixes) trees? Not sure which tree is the most common for picking GSMI
> stuff.

Picking out an individual patch from a series with as many responses and
threads like this one is quite difficult.

Just resend this as a stand-alone patch if you want it applied
stand-alone as our tools want to apply a whole patch series at once.

> I'm trying to get these fixes merged individually in their trees to not
> stall the whole series and increase the burden of re-submitting.

The burden is on the submitter, not the maintainer as we have more
submitters than reviewers/maintainers.

thanks,

greg k-h