Re: [PATCH v2] ALSA: pcm: Serialize snd_pcm_suspend_all() with open_mutex

[Takashi Iwai]

On Fri, 27 Mar 2026 14:59:45 +0100,
Cássio Gabriel wrote:
> 
> snd_pcm_suspend_all() walks all PCM substreams and uses a lockless
> runtime check to skip closed streams. It then calls snd_pcm_suspend()
> for each remaining substream and finally runs snd_pcm_sync_stop() in a
> second pass.
> 
> The runtime lifetime is still controlled by pcm->open_mutex in the
> open/release path. That means a concurrent close can clear or free
> substream->runtime after the initial check in snd_pcm_suspend_all(),
> leaving the later suspend or sync-stop path to dereference a stale or
> NULL runtime pointer.
> 
> Serialize snd_pcm_suspend_all() with pcm->open_mutex so the runtime
> pointer stays stable across both loops. This matches the existing PCM
> runtime lifetime rule already used by other core paths that access
> substream->runtime outside the stream lock.
> 
> Suggested-by: Takashi Iwai <tiwai@xxxxxxxx>
> Signed-off-by: Cássio Gabriel <cassiogabrielcontato@xxxxxxxxx>
> ---
> Changes in v2:
> - Update funtion description (updates kerneldoc).
> - Link to v1: https://lore.kernel.org/r/20260320-alsa-pcm-suspend-open-close-lock-v1-1-b5992a120335@xxxxxxxxx

Applied to for-next branch now.  Thanks.


Takashi