linux-kernel - Re: [PATCH] ALSA: firewire-tascam: add missing unwind goto in snd_tscm_stream_start

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Date:   Thu, 06 Apr 2023 16:46:10 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     Xu Biang <xubiang@...t.edu.cn>
Cc:     Clemens Ladisch <clemens@...isch.de>,
        Takashi Sakamoto <o-takashi@...amocchi.jp>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>, dzm91@...t.edu.cn,
        error27@...il.com, hust-os-kernel-patches@...glegroups.com,
        alsa-devel@...a-project.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ALSA: firewire-tascam: add missing unwind goto in snd_tscm_stream_start_duplex()

On Thu, 06 Apr 2023 15:28:01 +0200,
Xu Biang wrote:
> 
> Smatch Warns:
> sound/firewire/tascam/tascam-stream.c:493 snd_tscm_stream_start_duplex()
> warn: missing unwind goto?
> 
> The direct return will cause the stream list of "&tscm->domain" unemptied
> and the session in "tscm" unfinished if amdtp_domain_start() returns with
> an error.
> 
> Fix this by changing the direct return to a goto which will empty the
> stream list of "&tscm->domain" and finish the session in "tscm".
> 
> The snd_tscm_stream_start_duplex() function is called in the prepare
> callback of PCM. According to "ALSA Kernel API Documentation", the prepare
> callback of PCM will be called many times at each setup. So, if the
> "&d->streams" list is not emptied, when the prepare callback is called
> next time, snd_tscm_stream_start_duplex() will receive -EBUSY from
> amdtp_domain_add_stream() that tries to add an existing stream to the
> domain. The error handling code after the "error" label will be executed
> in this case, and the "&d->streams" list will be emptied. So not emptying
> the "&d->streams" list will not cause an issue. But it is more efficient
> and readable to empty it on the first error by changing the direct return
> to a goto statement.
> 
> The session in "tscm" has been begun before amdtp_domain_start(), so it
> needs to be finished when amdtp_domain_start() fails.
> 
> Fixes: c281d46a51e3 ("ALSA: firewire-tascam: support AMDTP domain")
> Signed-off-by: Xu Biang <xubiang@...t.edu.cn>
> Reviewed-by: Dan Carpenter <error27@...il.com>

Thanks, applied now.


Takashi