linux-kernel - Re: [PATCH v3 0/7] iopoll: Busy loop and timeout improvements + conversions

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Date:   Mon, 5 Jun 2023 17:08:14 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Geert Uytterhoeven <geert+renesas@...der.be>
Cc:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        Magnus Damm <magnus.damm@...il.com>,
        Joerg Roedel <joro@...tes.org>,
        Robin Murphy <robin.murphy@....com>,
        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>,
        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-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-renesas-soc@...r.kernel.org, linux-pm@...r.kernel.org,
        iommu@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 0/7] iopoll: Busy loop and timeout improvements + conversions

On Fri, Jun 2, 2023 at 10:51 AM Geert Uytterhoeven
<geert+renesas@...der.be> wrote:
> When implementing a polling loop, a common review comment is to use one
> of the read*_poll_timeout*() helpers.  Unfortunately this is not always
> possible, or might introduce subtle bugs.  This patch series aims to
> improve these helpers, so they can gain wider use.
>
>   1. The first patch improves busy-looping behavior of both the atomic
>      and non-atomic read*_poll_timeout*() helpers.
>      The issue addressed by this patch was discussed before[1-2], but I
>      am not aware of any patches moving forward.
>
>   2. The second patch fixes timeout handling of the atomic variants.
>      Some of the issues addressed by this patch were mitigated in
>      various places[3-5], and some of these findings may be of interest
>      to the authors of [6-8].
>
> The first two patches were sent before, and already received some acks
> and reviews.  I plan to queue these in an immutable and tagged branch
> after the weekend, for consumption by myself, and by other interested
> parties.

FTR...
The following changes since commit ac9a78681b921877518763ba0e89202254349d1b:

  Linux 6.4-rc1 (2023-05-07 13:34:35 -0700)

are available in the Git repository at:

  git://git.kernel.org/pub/scm/linux/kernel/git/geert/renesas-drivers.git
tags/iopoll-busy-loop-timeout-tag

for you to fetch changes up to 7349a69cf3125e92d48e442d9f400ba446fa314f:

  iopoll: Do not use timekeeping in read_poll_timeout_atomic()
(2023-06-05 15:35:27 +0200)

----------------------------------------------------------------
iopoll: Busy loop and timeout improvements

----------------------------------------------------------------
Geert Uytterhoeven (2):
      iopoll: Call cpu_relax() in busy loops
      iopoll: Do not use timekeeping in read_poll_timeout_atomic()

 include/linux/iopoll.h | 24 +++++++++++++++++++-----
 1 file changed, 19 insertions(+), 5 deletions(-)

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds