Re: [alsa-devel] [PATCH] ASoC: samsung: Use IRQ safe spin lock calls

[Sylwester Nawrocki <s.nawrocki@samsung.com>]

On 18/02/16 16:47, Charles Keepax wrote:
> Lockdep warns of a potential lock inversion, i2s->lock is held numerous
> times whilst we are under the substream lock (snd_pcm_stream_lock). If
> we use the IRQ unsafe spin lock calls, you can also end up locking
> snd_pcm_stream_lock whilst under i2s->lock (if an IRQ happens whilst we
> are holding i2s->lock). This could result in deadlock.
> 
> [   18.147001]        CPU0                    CPU1
> [   18.151509]        ----                    ----
> [   18.156022]   lock(&(&pri_dai->spinlock)->rlock);
> [   18.160701]                                local_irq_disable();
> [   18.166622]                                lock(&(&substream->self_group.lock)->rlock);
> [   18.174595]                                lock(&(&pri_dai->spinlock)->rlock);
> [   18.181806]   <Interrupt>
> [   18.184408]     lock(&(&substream->self_group.lock)->rlock);
> [   18.190045]
> [   18.190045]  *** DEADLOCK ***
> 
> This patch changes to using the irq safe spinlock calls, to avoid this
> issue.
> 
> Fixes: ce8bcdbb61d9 ("ASoC: samsung: i2s: Protect more registers with a spinlock")
> Signed-off-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>

Acked-by: Sylwester Nawrocki <s.nawrocki@samsung.com>