Re: [BUG] ALSA: core: pcm_memory: a possible data race in do_alloc_pages()

[Jaroslav Kysela]

On 26. 06. 23 9:33, Takashi Iwai wrote:
> On Mon, 26 Jun 2023 09:31:18 +0200,
> Tuo Li wrote:
> > Hello,
> >
> > Thank you for your reply!
>
> FWIW, the simplest fix would be something like below, just extending
> the mutex coverage.  But it'll serialize the all calls, so it might
> influence on the performance, while it's the safest way.

It may be better to update total_pcm_alloc_bytes before 
snd_dma_alloc_dir_pages() call and decrease this value when allocation fails 
to allow parallel allocations. Then the mutex can be held only for the 
total_pcm_alloc_bytes variable update.

Eventually, total_pcm_alloc_bytes may be atomic.

					Jaroslav

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