Re: [PATCH] ALSA: control: Take power_ref lock primarily

[Jaroslav Kysela <perex@xxxxxxxx>]

On 29. 07. 24 18:06, Takashi Iwai wrote:
> The code path for kcontrol accesses have often nested locks of both
> card's controls_rwsem and power_ref, and applies in that order.
> However, what could take much longer is the latter, power_ref; it
> waits for the power state of the device, and it pretty much depends on
> the user's action.
>
> This patch swaps the locking order of those locks to a more natural
> way, namely, power_ref -> controls_rwsem, in order to shorten the time
> of possible nested locks.  For consistency, power_ref is taken always
> in the top-level caller side (that is, *_user() functions and the
> ioctl handler itself).
>
> Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>

It looks fine, but perhaps, we can DEFINE_GUARD for snd_power_ref_and_wait and 
use this scoped guard, too? It would greatly simplify code.

					Jaroslav

--
Jaroslav Kysela <perex@xxxxxxxx>
Linux Sound Maintainer; ALSA Project; Red Hat, Inc.