linux-kernel - Re: [PATCH v3 0/5] MIPS: Add per-cpu IRQ stack

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Date:   Fri, 13 Jan 2017 09:49:39 +0000
From:   James Hogan <james.hogan@...tec.com>
To:     "Jason A. Donenfeld" <Jason@...c4.com>
CC:     Ralf Baechle <ralf@...ux-mips.org>,
        Matt Redfearn <matt.redfearn@...tec.com>,
        <linux-mips@...ux-mips.org>, Thomas Gleixner <tglx@...utronix.de>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Marcin Nowakowski <marcin.nowakowski@...tec.com>,
        Chris Metcalf <cmetcalf@...lanox.com>,
        Petr Mladek <pmladek@...e.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Adam Buchbinder <adam.buchbinder@...il.com>,
        Paul Burton <paul.burton@...tec.com>,
        Jiri Slaby <jslaby@...e.cz>,
        "Maciej W. Rozycki" <macro@...tec.com>,
        Aaron Tomlin <atomlin@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v3 0/5] MIPS: Add per-cpu IRQ stack

On Thu, Jan 12, 2017 at 12:32:52AM +0100, Jason A. Donenfeld wrote:
> On Wed, Jan 11, 2017 at 2:20 AM, Ralf Baechle <ralf@...ux-mips.org> wrote:
> > On Wed, Jan 11, 2017 at 12:32:38AM +0100, Jason A. Donenfeld wrote:
> >
> >> Was this ever picked up for 4.10 or 4.11?
> >
> > Still sitting in -next as commit 3cc3434fd630 and its four parent commits.
> 
> Oh, good, so it's progressing normally. I just didn't see any
> acknowledgement on this thread so I was worried.
> 
> Can this propagate to stable? A few OpenWRT MIPS people are
> complaining to me about sporadic crashes when stacking too many
> virtual network drivers (batman over gre over ppp over ...), which is
> solved by this patchset.
> 
> Jason

Its quite a significant change/feature, especially in terms of potential
for further breakage. I don't think its really stable material to be
honest.

The actual stable kernel rules are here though:
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/stable-kernel-rules.rst

Do the OpenWRT issues affect mainline kernels? (if its due to excessive
stack frame sizes in out of tree code, then that should be fixed out of
tree). It sounds bad if the kernel stack requirement can be made
arbitrarily large by stacking too many drivers.

Is there a simpler fix/workaround for the issue that would satisfy
stable kernel users until they can upgrade to a kernel with irqstacks?

Cheers
James

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