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From:   Linus Walleij <linus.walleij@linaro.org>
Date:   Mon, 1 Oct 2018 11:37:07 +0200
Message-ID: <CACRpkdbxh3uoVbc1udouxKaN+sc+q_vB7oj_B8PEa4wi=wLedg@mail.gmail.com>
Subject: Re: [PATCH] gpiolib: Fix incorrect use of find_next_zero_bit()
To:     Janusz Krzysztofik <jmkrzyszt@gmail.com>
Cc:     Miguel Ojeda Sandonis <miguel.ojeda.sandonis@gmail.com>,
        Peter Korsgaard <peter.korsgaard@barco.com>,
        Peter Rosin <peda@axentia.se>,
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On Sat, Sep 29, 2018 at 2:19 PM Janusz Krzysztofik <jmkrzyszt@gmail.com> wrote:

> Commit b17566a6b08b ("gpiolib: Implement fast processing path in
> get/set array"), already fixed to some extent with commit 5d581d7e8cdc
> ("gpiolib: Fix missing updates of bitmap index"), introduced a new mode
> of processing bitmaps where bits applicable for fast bitmap processing
> path are supposed to be skipped while iterating bits which don't apply.
> Unfortunately, find_next_zero_bit() function supposed to skip over
> those fast bits is always called with a 'start' argument equal to an
> index of last zero bit found and returns that index value again an
> again, causing an infinite loop.
>
> Fix it by incrementing the index uncoditionally before
> find_next_zero_bit() is optionally called.
>
> Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
> Signed-off-by: Janusz Krzysztofik <jmkrzyszt@gmail.com>

Patch applied with Marek's Tested-by.

Thanks to both of you for digging in and fixing this up!
Now we are in good shape for the v4.20 cycle :)

Yours,
Linus Walleij