From: Jacek Anaszewski <jacek.anaszewski@gmail.com>
To: Heiner Kallweit <hkallweit1@gmail.com>
Cc: linux-leds@vger.kernel.org, Jacek Anaszewski <j.anaszewski@samsung.com>
Subject: Re: Locking in LED core really not needed or missing?
Date: Sun, 10 Jan 2016 09:17:31 +0100 [thread overview]
Message-ID: <5692139B.3070804@gmail.com> (raw)
In-Reply-To: <56901C90.2050801@gmail.com>
Hi Heiner,
On 01/08/2016 09:31 PM, Heiner Kallweit wrote:
> I'm a little puzzled about the more or less completely missing locking in the LED core.
>
> Let's just take led_timer_function as example.
> It modifies led_cdev->flags and led_cdev->brightness from soft irq context
> (soft blink timer) w/o locking. Accessing these fields is not guaranteed to be atomic
> and the function doesn't even use set_bit etc. for modifying the bitmap.
>
> And brightness_set and other exported functions can even be called from
> hard irq context (e.g. by triggers).
led_set_brightness() behaves differently when blink timer is enabled.
This issue was initially addressed by the patch [1].
Currently even more related improvements sit on linux-next.
> This seems to be quite unsafe to me. Just think of a soft or hard irq colliding
> with a sysfs access. IMHO it's just due to the fact that these collision scenarios
> are relatively unlikely that we don't have problems.
> Am I missing something or is this actually an open issue?
> --
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>
[1] http://www.spinics.net/lists/linux-leds/msg00006.html
--
Best Regards,
Jacek Anaszewski
prev parent reply other threads:[~2016-01-10 8:17 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-08 20:31 Locking in LED core really not needed or missing? Heiner Kallweit
2016-01-10 8:17 ` Jacek Anaszewski [this message]
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