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authorTakashi Iwai <tiwai@suse.de>2014-11-04 16:52:28 +0100
committerMark Brown <broonie@kernel.org>2014-11-04 17:18:32 +0000
commitea9d0d771fcd32cd56070819749477d511ec9117 (patch)
tree6471b62340c799e9604b92fdabdd3c0a97671182 /include
parentf114040e3ea6e07372334ade75d1ee0775c355e1 (diff)
ASoC: dpcm: Fix race between FE/BE updates and trigger
DPCM can update the FE/BE connection states totally asynchronously from the FE's PCM state. Most of FE/BE state changes are protected by mutex, so that they won't race, but there are still some actions that are uncovered. For example, suppose to switch a BE while a FE's stream is running. This would call soc_dpcm_runtime_update(), which sets FE's runtime_update flag, then sets up and starts BEs, and clears FE's runtime_update flag again. When a device emits XRUN during this operation, the PCM core triggers snd_pcm_stop(XRUN). Since the trigger action is an atomic ops, this isn't blocked by the mutex, thus it kicks off DPCM's trigger action. It eventually updates and clears FE's runtime_update flag while soc_dpcm_runtime_update() is running concurrently, and it results in confusion. Usually, for avoiding such a race, we take a lock. There is a PCM stream lock for that purpose. However, as already mentioned, the trigger action is atomic, and we can't take the lock for the whole soc_dpcm_runtime_update() or other operations that include the lengthy jobs like hw_params or prepare. This patch provides an alternative solution. This adds a way to defer the conflicting trigger callback to be executed at the end of FE/BE state changes. For doing it, two things are introduced: - Each runtime_update state change of FEs is protected via PCM stream lock. - The FE's trigger callback checks the runtime_update flag. If it's not set, the trigger action is executed there. If set, mark the pending trigger action and returns immediately. - At the exit of runtime_update state change, it checks whether the pending trigger is present. If yes, it executes the trigger action at this point. Reported-and-tested-by: Qiao Zhou <zhouqiao@marvell.com> Signed-off-by: Takashi Iwai <tiwai@suse.de> Acked-by: Liam Girdwood <liam.r.girdwood@linux.intel.com> Signed-off-by: Mark Brown <broonie@kernel.org> Cc: stable@vger.kernel.org
Diffstat (limited to 'include')
-rw-r--r--include/sound/soc-dpcm.h2
1 files changed, 2 insertions, 0 deletions
diff --git a/include/sound/soc-dpcm.h b/include/sound/soc-dpcm.h
index 2883a7a6f9f3..98f2ade0266e 100644
--- a/include/sound/soc-dpcm.h
+++ b/include/sound/soc-dpcm.h
@@ -102,6 +102,8 @@ struct snd_soc_dpcm_runtime {
/* state and update */
enum snd_soc_dpcm_update runtime_update;
enum snd_soc_dpcm_state state;
+
+ int trigger_pending; /* trigger cmd + 1 if pending, 0 if not */
};
/* can this BE stop and free */