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From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Mon, 5 Jun 2023 17:08:14 +0200
Message-ID: <CAMuHMdXrgyWT=RtS6cuUP6sT-Ta9Oa4cU2kHP10ah-U50DOSsg@mail.gmail.com>
Subject: Re: [PATCH v3 0/7] iopoll: Busy loop and timeout improvements + conversions
To:     Geert Uytterhoeven <geert+renesas@glider.be>
Cc:     Michael Turquette <mturquette@baylibre.com>,
        Stephen Boyd <sboyd@kernel.org>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>,
        Magnus Damm <magnus.damm@gmail.com>,
        Joerg Roedel <joro@8bytes.org>,
        Robin Murphy <robin.murphy@arm.com>,
        Tomasz Figa <tomasz.figa@gmail.com>,
        Sylwester Nawrocki <s.nawrocki@samsung.com>,
        Will Deacon <will@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
        Wolfram Sang <wsa+renesas@sang-engineering.com>,
        Dejin Zheng <zhengdejin5@gmail.com>,
        Kai-Heng Feng <kai.heng.feng@canonical.com>,
        Nicholas Piggin <npiggin@gmail.com>,
        Heiko Carstens <hca@linux.ibm.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Russell King <linux@armlinux.org.uk>,
        John Stultz <jstultz@google.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Tony Lindgren <tony@atomide.com>,
        Krzysztof Kozlowski <krzk@kernel.org>,
        Tero Kristo <tero.kristo@linux.intel.com>,
        Ulf Hansson <ulf.hansson@linaro.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        linux-clk@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-renesas-soc@vger.kernel.org, linux-pm@vger.kernel.org,
        iommu@lists.linux.dev, linux-kernel@vger.kernel.org
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On Fri, Jun 2, 2023 at 10:51 AM Geert Uytterhoeven
<geert+renesas@glider.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@linux-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