sound: pcm: record a substream's owner process

Record the pid of the task that opened a PCM substream. For sound
cards with hardware mixing, this allows determining which process
is associated with a specific substream's volume control.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

2 files changed, 7 insertions, 0 deletions

diff --git a/include/sound/pcm.h b/include/sound/pcm.h
index de6d981de5d6..c83a4a79f16b 100644
--- a/include/sound/pcm.h
+++ b/include/sound/pcm.h
@@ -348,6 +348,8 @@ struct snd_pcm_group {		/* keep linked substreams */
         int count;
 };
 
+struct pid;
+
 struct snd_pcm_substream {
         struct snd_pcm *pcm;
         struct snd_pcm_str *pstr;
@@ -379,6 +381,7 @@ struct snd_pcm_substream {
         atomic_t mmap_count;
         unsigned int f_flags;
         void (*pcm_release)(struct snd_pcm_substream *);
+        struct pid *pid;
 #if defined(CONFIG_SND_PCM_OSS) || defined(CONFIG_SND_PCM_OSS_MODULE)
         /* -- OSS things -- */
         struct snd_pcm_oss_substream oss;
diff --git a/sound/core/pcm.c b/sound/core/pcm.c
index 8e2c7833614c..6884ae031f6f 100644
--- a/sound/core/pcm.c
+++ b/sound/core/pcm.c
@@ -435,6 +435,7 @@ static void snd_pcm_substream_proc_status_read(struct snd_info_entry *entry,
                 return;
         }
         snd_iprintf(buffer, "state: %s\n", snd_pcm_state_name(status.state));
+        snd_iprintf(buffer, "owner_pid   : %d\n", pid_vnr(substream->pid));
         snd_iprintf(buffer, "trigger_time: %ld.%09ld\n",
                 status.trigger_tstamp.tv_sec, status.trigger_tstamp.tv_nsec);
         snd_iprintf(buffer, "tstamp      : %ld.%09ld\n",
@@ -900,6 +901,7 @@ int snd_pcm_attach_substream(struct snd_pcm *pcm, int stream,
         substream->private_data = pcm->private_data;
         substream->ref_count = 1;
         substream->f_flags = file->f_flags;
+        substream->pid = get_pid(task_pid(current));
         pstr->substream_opened++;
         *rsubstream = substream;
         return 0;
@@ -921,6 +923,8 @@ void snd_pcm_detach_substream(struct snd_pcm_substream *substream)
         kfree(runtime->hw_constraints.rules);
         kfree(runtime);
         substream->runtime = NULL;
+        put_pid(substream->pid);
+        substream->pid = NULL;
         substream->pstr->substream_opened--;
 }