On Wed, 23 Mar 2022 09:15:19 +0100, Takashi Iwai wrote:
On Wed, 23 Mar 2022 09:08:25 +0100, Amadeusz SX2awiX4ski wrote:
On 3/22/2022 6:07 PM, Takashi Iwai wrote:
Like the previous fixes to hw_params and hw_free ioctl races, we need to paper over the concurrent prepare ioctl calls against hw_params and hw_free, too.
This patch implements the locking with the existing runtime->buffer_mutex for prepare ioctls. Unlike the previous case for snd_pcm_hw_hw_params() and snd_pcm_hw_free(), snd_pcm_prepare() is performed to the linked streams, hence the lock can't be applied simply on the top. For tracking the lock in each linked substream, we modify snd_pcm_action_group() slightly and apply the buffer_mutex for the case stream_lock=false (formerly there was no lock applied) there.
Cc: stable@vger.kernel.org Signed-off-by: Takashi Iwai tiwai@suse.de
sound/core/pcm_native.c | 32 ++++++++++++++++++-------------- 1 file changed, 18 insertions(+), 14 deletions(-)
diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c index 266895374b83..0e4fbf5fd87b 100644 --- a/sound/core/pcm_native.c +++ b/sound/core/pcm_native.c @@ -1190,15 +1190,17 @@ struct action_ops { static int snd_pcm_action_group(const struct action_ops *ops, struct snd_pcm_substream *substream, snd_pcm_state_t state,
bool do_lock)
bool stream_lock)
if (do_lock && s != substream) {if (s->pcm->nonatomic)
if (s != substream) {if (!stream_lock)mutex_lock_nested(&s->runtime->buffer_mutex, depth);else if (s->pcm->nonatomic) mutex_lock_nested(&s->self_group.mutex, depth); else spin_lock_nested(&s->self_group.lock, depth);Maybe if (!stream_lock) mutex_lock_nested(&s->runtime->buffer_mutex, depth); else snd_pcm_group_lock(&s->self_group, s->pcm->nonatomic); ?
No, it must be nested locks with the given subclass.
FWIW, the reason is that lockdep would complain otherwise as if it were a deadlock. That is, this is a workaround for avoiding false lockdep warnings.
Takashi