linux-kernel - Re: [PATCH] ACPI / video: driver must be registered before checking for keypresses

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Message-ID: <20160106173811.GA4561@hudson.localdomain>
Date:	Wed, 6 Jan 2016 09:38:11 -0800
From:	Jeremiah Mahler <jmmahler@...il.com>
To:	Adrien Schildknecht <adrien+dev@...ischi.me>
Cc:	rui.zhang@...el.com, rjw@...ysocki.net, lenb@...nel.org,
	hdegoede@...hat.com, linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ACPI / video: driver must be registered before checking
 for keypresses

all,

On Mon, Jan 04, 2016 at 11:22:28PM +0100, Adrien Schildknecht wrote:
> acpi_video_handles_brightness_key_presses() may use an uninitialized mutex.
> The error has been reported by lockdep: DEBUG_LOCKS_WARN_ON(l->magic != l).
> The function assumes that the video driver has been registered before being
> called. As explained in the comment of acpi_video_init(), the registration
> of the video class may be defered and thus may not take place in the init
> function of the module.
> 
> Use completion mechanisms to make sure that
> acpi_video_handles_brightness_key_presses() wait for the completion of
> acpi_video_register() before using the mutex.
> Also get rid of register_count since task completion can replace it.
> 
> Signed-off-by: Adrien Schildknecht <adrien+dev@...ischi.me>
> ---
>  drivers/acpi/acpi_video.c | 27 ++++++++++++++-------------
>  1 file changed, 14 insertions(+), 13 deletions(-)
> 
[...]

This patch does fix the problem I was having [1].  Thanks for the fix.

  [1]: https://lkml.org/lkml/2016/1/4/791

Tested-by: Jeremiah Mahler <jmmahler@...il.com>

-- 
- Jeremiah Mahler
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