[alsa-devel] [BUG] sound/soc/samsung: a possible sleep-in-atomic bugs in s3c_pcm_hw_params

[Krzysztof Kozlowski]

On Tue, Dec 12, 2017 at 2:24 AM, Jia-Ju Bai <baijiaju1990 at 163.com> wrote:
> According to sound/soc/samsung/pcm.c, the kernel module may sleep under a
> spinlock.
> The function call path is:
> s3c_pcm_hw_params (acquire the spinlock)
>   clk_get_rate
>     clk_core_get_rate
>       clk_prepare_lock
>         mutex_lock --> may sleep
>
> I do not find a good way to fix it, so I only report.
> This possible bug is found by my static analysis tool (DSAC) and my code
> review.

Thanks for the report. Your finding looks correct, the code might
sleep under spinlock.

I do not see easy solution. Maybe the readl(regs + S3C_PCM_CLKCTL) and
clk_get_rate() could be moved before spinlock. The second path
modifying it - s3c_pcm_set_sysclk() - is not protected by it. The
spinlock is not effective around it.

Best regards,
Krzysztof