linux-kernel - Re: [PATCH 1/2] ASoC: max98090: fix incorrect helper in max98090_dapm_put_enum

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Message-ID: <CA+Px+wUo7i331kEuc2mjE9uqSna7Lxnua=hvgPc+0T2YdeCgMg@mail.gmail.com>
Date:   Thu, 9 Jan 2020 13:11:38 +0800
From:   Tzung-Bi Shih <tzungbi@...gle.com>
To:     Marek Szyprowski <m.szyprowski@...sung.com>
Cc:     ALSA development <alsa-devel@...a-project.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Samsung SOC <linux-samsung-soc@...r.kernel.org>,
        Mark Brown <broonie@...nel.org>,
        Sylwester Nawrocki <s.nawrocki@...sung.com>,
        Dylan Reid <dgreid@...gle.com>,
        Jimmy Cheng-Yi Chiang <cychiang@...gle.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: Re: [PATCH 1/2] ASoC: max98090: fix incorrect helper in max98090_dapm_put_enum_double()

On Wed, Jan 8, 2020 at 7:50 PM Marek Szyprowski
<m.szyprowski@...sung.com> wrote:
> Fixes: 62d5ae4cafb7 ("ASoC: max98090: save and restore SHDN when changing sensitive registers")
> Signed-off-by: Marek Szyprowski <m.szyprowski@...sung.com>
Reviewed-by: Tzung-Bi Shih <tzungbi@...gle.com>

Thanks for finding and fixing the bug.

The fix also reminded me: there are two possible "context" to call
max98090_dapm_put_enum_double( ): DAPM and userspace mixer control.
- max98090_shdn_save( ) is designed for mixer control because it
acquires dapm_mutex.
- max98090_shdn_save_locked( ) is designed for DAPM without acquiring lock.

Current code:
> +static int max98090_dapm_put_enum_double(struct snd_kcontrol *kcontrol,
[snip]
> + max98090_shdn_save(max98090);
> + ret = snd_soc_dapm_put_enum_double(kcontrol, ucontrol);
> + max98090_shdn_restore(max98090);

Should it cause a deadlock if DAPM calls the
max98090_dapm_put_enum_double( )?  I didn't see a deadlock last time I
tested the series.  Will do further analysis on this.