> Concurrent non-atomic actions on different members of a linked PCM group
> currently lock their own buffer first, then the other members. That
> acquisition order can differ between callers. Sibling buffer mutexes
> also do not close their buffer-access admission counters.
>
> Close buffer access for every member before taking any buffer mutex, and
> acquire those mutexes in the stable linked-list order while group
> membership is protected. Release every access gate on success and on
> failure, including when a member already has an active buffer access.
> The group action then uses the buffers already held by its caller.
>
> The PCM stream and group locks are not held across sleeping driver
> prepare callbacks. Single-stream non-atomic actions keep their existing
> buffer-access locking path.
>
> Fixes: 3c3201f8c7bb ("ALSA: pcm: Fix races among concurrent prepare and
> hw_params/hw_free calls")
> Fixes: bc55cfd5718c ("ALSA: pcm: Fix potential AB/BA lock with buffer_mutex
> and mmap_lock")
> Assisted-by: LLM
> Signed-off-by: Joonho Lee <[email protected]>
Sashiko has reviewed this patch and found no issues.
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https://sashiko.dev/#/patchset/[email protected]?part=5
