linux-kernel - Re: [PATCH 0/3] IRQ stack support for ARM

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Date:   Wed, 21 Oct 2020 14:46:28 +0200
From:   Arnd Bergmann <arnd@...nel.org>
To:     Russell King - ARM Linux admin <linux@...linux.org.uk>
Cc:     Arnd Bergmann <arnd@...nel.org>,
        Maninder Singh <maninder1.s@...sung.com>, v.narang@...sung.com,
        a.sahrawat@...sung.com, Andrew Morton <akpm@...ux-foundation.org>,
        Marc Zyngier <maz@...nel.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Vincent Whitchurch <vincent.whitchurch@...s.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Valentin Schneider <valentin.schneider@....com>,
        Dmitry Safonov <0x7f454c46@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Nathan Huckleberry <nhuck@...gle.com>,
        Will Deacon <will@...nel.org>, Jian Cai <caij2003@...il.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
Subject: Re: [PATCH 0/3] IRQ stack support for ARM

On Wed, Oct 21, 2020 at 2:34 PM Russell King - ARM Linux admin
<linux@...linux.org.uk> wrote:
>
> We don't do it because we don't have a separate register to be able
> to store the thread_info pointer, and copying that lump between the
> SVC and IRQ stack will add massively to IRQ latency, especially for
> older machines.

I forwarded my other reply as well, in which I suggested using
CONFIG_THREAD_INFO_IN_TASK, wouldn't that solve the problem?

      Arnd