linux-kernel - Re: [PATCH v2 2/2] iopoll: Do not use timekeeping in read_poll_timeout

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Message-Id: <c6966111-cea0-4547-8463-46f9f767c20f@app.fastmail.com>
Date:   Wed, 10 May 2023 15:56:39 +0200
From:   "Arnd Bergmann" <arnd@...db.de>
To:     "Geert Uytterhoeven" <geert@...ux-m68k.org>
Cc:     "Stephen Boyd" <sboyd@...nel.org>,
        "Tomasz Figa" <tomasz.figa@...il.com>,
        "Sylwester Nawrocki" <s.nawrocki@...sung.com>,
        "Will Deacon" <will@...nel.org>,
        "Wolfram Sang" <wsa+renesas@...g-engineering.com>,
        "Dejin Zheng" <zhengdejin5@...il.com>,
        "Kai-Heng Feng" <kai.heng.feng@...onical.com>,
        "Nicholas Piggin" <npiggin@...il.com>,
        "Heiko Carstens" <hca@...ux.ibm.com>,
        "Peter Zijlstra" <peterz@...radead.org>,
        "Russell King" <linux@...linux.org.uk>,
        "John Stultz" <jstultz@...gle.com>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        "Tony Lindgren" <tony@...mide.com>,
        "Krzysztof Kozlowski" <krzk@...nel.org>,
        "Tero Kristo" <tero.kristo@...ux.intel.com>,
        "Ulf Hansson" <ulf.hansson@...aro.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        "Vincent Guittot" <vincent.guittot@...aro.org>,
        linux-arm-kernel@...ts.infradead.org,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] iopoll: Do not use timekeeping in
 read_poll_timeout_atomic()

On Wed, May 10, 2023, at 15:46, Geert Uytterhoeven wrote:
> I first ran into it when converting open-coded loops to
> read*_poll_timeout_atomic().
> Later, I also saw the issue with the existing
> read*_poll_timeout_atomic() calls in the R-Car SYSC driver, but only
> after applying additional patches from the BSP that impact the moment
> PM Domains are powered during s2ram.

Ok

> The various pointers to existing mitigations in the cover letter should
> give you other suggestions for how to reproduce...

I see the cover letter now, I thought I had looked for it earlier but
didn't notice it.

     Arnd