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

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Date:   Mon, 8 Aug 2022 17:26:43 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     "Guilherme G. Piccoli" <gpiccoli@...lia.com>
Cc:     Evan Green <evgreen@...omium.org>, linux-efi@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        Ard Biesheuvel <ardb@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>, bhe@...hat.com,
        Petr Mladek <pmladek@...e.com>, kexec@...ts.infradead.org,
        linux-hyperv@...r.kernel.org, netdev@...r.kernel.org,
        x86@...nel.org, kernel-dev@...lia.com, kernel@...ccoli.net,
        halves@...onical.com, fabiomirmar@...il.com,
        alejandro.j.jimenez@...cle.com,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>,
        Jonathan Corbet <corbet@....net>, d.hatayama@...fujitsu.com,
        dave.hansen@...ux.intel.com, dyoung@...hat.com,
        feng.tang@...el.com, mikelley@...rosoft.com,
        hidehiro.kawai.ez@...achi.com, jgross@...e.com,
        john.ogness@...utronix.de, Kees Cook <keescook@...omium.org>,
        luto@...nel.org, mhiramat@...nel.org, mingo@...hat.com,
        paulmck@...nel.org, peterz@...radead.org, rostedt@...dmis.org,
        senozhatsky@...omium.org, Alan Stern <stern@...land.harvard.edu>,
        Thomas Gleixner <tglx@...utronix.de>, vgoyal@...hat.com,
        vkuznets@...hat.com, Will Deacon <will@...nel.org>,
        David Gow <davidgow@...gle.com>,
        Julius Werner <jwerner@...omium.org>
Subject: Re: [PATCH v2 03/13] firmware: google: Test spinlock on panic path
 to avoid lockups

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@...lia.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@...nel.org>
> >> Cc: David Gow <davidgow@...gle.com>
> >> Cc: Evan Green <evgreen@...omium.org>
> >> Cc: Julius Werner <jwerner@...omium.org>
> >> Signed-off-by: Guilherme G. Piccoli <gpiccoli@...lia.com>
> > 
> > Reviewed-by: Evan Green <evgreen@...omium.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