linux-kernel - Re: [PATCH v2] ALSA: pcmtest: stop timer in the hw

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Message-ID: <d2534c1b-b654-42a3-9edb-3041ed6bfe01@gmail.com>
Date:   Wed, 6 Dec 2023 20:03:58 +0000
From:   Ivan Orlov <ivan.orlov0322@...il.com>
To:     Takashi Iwai <tiwai@...e.de>
Cc:     tiwai@...e.com, perex@...ex.cz, linux-sound@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] ALSA: pcmtest: stop timer in the hw_free callback

On 12/6/23 16:59, Takashi Iwai wrote:
> On Wed, 06 Dec 2023 16:10:46 +0100,
> Ivan Orlov wrote:
>>
>> Stop timer in the 'hw_free' callback instead of the 'close' callback
>> since we want the timer to be stopped before the DMA buffer is released.
>> Otherwise, it could trigger a kernel panic in some circumstances, for
>> instance when the DMA buffer is already released but the timer callback
>> is still running.
> 
> You can't call timer_shutdown_sync() at hw_free.  The PCM stream is
> still there and you can re-setup via hw_params without closing.  But,
> after timer_shutdown_sync(), the timer instance must not be used any
> longer.
> 
> A more proper way would be to call timer_delete() (no sync) at trigger
> STOP, then call timer_delete_sync() at sync_stop op in addition.  This
> assures the immediate stop and the sync before changing to another PCM
> state.
> 
> timer_shutdown_sync() can be kept at the close op to be sure.
> 
> 
> thanks,
> 
> Takashi
> 

Hi Takashi,

Thanks a lot for the review, sounds reasonable, I'll make suggested 
changes and send the version 3 :)

--
Kind regards,
Ivan Orlov