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authorTakashi Iwai <tiwai@suse.de>2014-08-29 15:32:29 +0200
committerTakashi Iwai <tiwai@suse.de>2014-09-03 14:04:08 +0200
commit257f8cce5d40b811d229ed71602882baa0012808 (patch)
tree190a239257c625539a1b157acb3bd0075cdb61dc /sound/core/pcm.c
parent52addcf9d6669fa439387610bc65c92fa0980cef (diff)
downloadlinux-linaro-stable-257f8cce5d40b811d229ed71602882baa0012808.tar.gz
ALSA: pcm: Allow nonatomic trigger operations
Currently, many PCM operations are performed in a critical section protected by spinlock, typically the trigger and pointer callbacks are assumed to be atomic. This is basically because some trigger action (e.g. PCM stop after drain or xrun) is done in the interrupt handler. If a driver runs in a threaded irq, however, this doesn't have to be atomic. And many devices want to handle trigger in a non-atomic context due to lengthy communications. This patch tries all PCM calls operational in non-atomic context. What it does is very simple: replaces the substream spinlock with the corresponding substream mutex when pcm->nonatomic flag is set. The driver that wants to use the non-atomic PCM ops just needs to set the flag and keep the rest as is. (Of course, it must not handle any PCM ops in irq context.) Note that the code doesn't check whether it's atomic-safe or not, but trust in 100% that the driver sets pcm->nonatomic correctly. One possible problem is the case where linked PCM substreams have inconsistent nonatomic states. For avoiding this, snd_pcm_link() returns an error if one tries to link an inconsistent PCM substream. Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'sound/core/pcm.c')
-rw-r--r--sound/core/pcm.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/sound/core/pcm.c b/sound/core/pcm.c
index 43932e8dce66..afccdc553ef9 100644
--- a/sound/core/pcm.c
+++ b/sound/core/pcm.c
@@ -698,6 +698,7 @@ int snd_pcm_new_stream(struct snd_pcm *pcm, int stream, int substream_count)
}
substream->group = &substream->self_group;
spin_lock_init(&substream->self_group.lock);
+ mutex_init(&substream->self_group.mutex);
INIT_LIST_HEAD(&substream->self_group.substreams);
list_add_tail(&substream->link_list, &substream->self_group.substreams);
atomic_set(&substream->mmap_count, 0);