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

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Message-ID: <20230511064805.GF14287@atomide.com>
Date:   Thu, 11 May 2023 09:48:05 +0300
From:   Tony Lindgren <tony@...mide.com>
To:     Geert Uytterhoeven <geert+renesas@...der.be>
Cc:     Stephen Boyd <sboyd@...nel.org>,
        Tomasz Figa <tomasz.figa@...il.com>,
        Sylwester Nawrocki <s.nawrocki@...sung.com>,
        Will Deacon <will@...nel.org>, Arnd Bergmann <arnd@...db.de>,
        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>,
        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-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()

Hi,

* Geert Uytterhoeven <geert+renesas@...der.be> [230510 13:23]:
> read_poll_timeout_atomic() uses ktime_get() to implement the timeout
> feature, just like its non-atomic counterpart.  However, there are
> several issues with this, due to its use in atomic contexts:
> 
>   1. When called in the s2ram path (as typically done by clock or PM
>      domain drivers), timekeeping may be suspended, triggering the
>      WARN_ON(timekeeping_suspended) in ktime_get():

Maybe add a comment to read_poll_timeout_atomic() saying it can be
used also with timekeeping_suspended?

Otherwise a few years later it might get broken when somebody goes
to patch it without testing it with timekeeping_suspended :)

Other than that looks good to me:

Reviewed-by: Tony Lindgren <tony@...mide.com>