[media] em28xx-audio: fix some locking issues

Those locking issues affect tvtime, causing a kernel oops/panic, due to
a race condition.

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

2 files changed, 42 insertions, 50 deletions

diff --git a/drivers/media/video/em28xx/em28xx-audio.c b/drivers/media/video/em28xx/em28xx-audio.c
index e182abf476c..3c48a72eb7d 100644
--- a/drivers/media/video/em28xx/em28xx-audio.c
+++ b/drivers/media/video/em28xx/em28xx-audio.c
@@ -102,6 +102,9 @@ static void em28xx_audio_isocirq(struct urb *urb)
                 break;
         }
 
+        if (atomic_read(&dev->stream_started) == 0)
+                return;
+
         if (dev->adev.capture_pcm_substream) {
                 substream = dev->adev.capture_pcm_substream;
                 runtime = substream->runtime;
@@ -217,31 +220,6 @@ static int em28xx_init_audio_isoc(struct em28xx *dev)
         return 0;
 }
 
-static int em28xx_cmd(struct em28xx *dev, int cmd, int arg)
-{
-        dprintk("%s transfer\n", (dev->adev.capture_stream == STREAM_ON) ?
-                                 "stop" : "start");
-
-        switch (cmd) {
-        case EM28XX_CAPTURE_STREAM_EN:
-                if (dev->adev.capture_stream == STREAM_OFF &&
-                    arg == EM28XX_START_AUDIO) {
-                        dev->adev.capture_stream = STREAM_ON;
-                        em28xx_init_audio_isoc(dev);
-                } else if (dev->adev.capture_stream == STREAM_ON &&
-                           arg == EM28XX_STOP_AUDIO) {
-                        dev->adev.capture_stream = STREAM_OFF;
-                        em28xx_deinit_isoc_audio(dev);
-                } else {
-                        em28xx_errdev("An underrun very likely occurred. "
-                                        "Ignoring it.\n");
-                }
-                return 0;
-        default:
-                return -EINVAL;
-        }
-}
-
 static int snd_pcm_alloc_vmalloc_buffer(struct snd_pcm_substream *subs,
                                         size_t size)
 {
@@ -303,7 +281,6 @@ static int snd_em28xx_capture_open(struct snd_pcm_substream *substream)
         dev->mute = 0;
         mutex_lock(&dev->lock);
         ret = em28xx_audio_analog_set(dev);
-        mutex_unlock(&dev->lock);
         if (ret < 0)
                 goto err;
 
@@ -311,11 +288,10 @@ static int snd_em28xx_capture_open(struct snd_pcm_substream *substream)
         if (dev->alt == 0 && dev->adev.users == 0) {
                 int errCode;
                 dev->alt = 7;
-                errCode = usb_set_interface(dev->udev, 0, 7);
                 dprintk("changing alternate number to 7\n");
+                errCode = usb_set_interface(dev->udev, 0, 7);
         }
 
-        mutex_lock(&dev->lock);
         dev->adev.users++;
         mutex_unlock(&dev->lock);
 
@@ -325,6 +301,8 @@ static int snd_em28xx_capture_open(struct snd_pcm_substream *substream)
 
         return 0;
 err:
+        mutex_unlock(&dev->lock);
+
         em28xx_err("Error while configuring em28xx mixer\n");
         return ret;
 }
@@ -338,6 +316,11 @@ static int snd_em28xx_pcm_close(struct snd_pcm_substream *substream)
         dev->mute = 1;
         mutex_lock(&dev->lock);
         dev->adev.users--;
+        if (atomic_read(&dev->stream_started) > 0) {
+                atomic_set(&dev->stream_started, 0);
+                schedule_work(&dev->wq_trigger);
+        }
+
         em28xx_audio_analog_set(dev);
         if (substream->runtime->dma_area) {
                 dprintk("freeing\n");
@@ -375,8 +358,10 @@ static int snd_em28xx_hw_capture_free(struct snd_pcm_substream *substream)
 
         dprintk("Stop capture, if needed\n");
 
-        if (dev->adev.capture_stream == STREAM_ON)
-                em28xx_cmd(dev, EM28XX_CAPTURE_STREAM_EN, EM28XX_STOP_AUDIO);
+        if (atomic_read(&dev->stream_started) > 0) {
+                atomic_set(&dev->stream_started, 0);
+                schedule_work(&dev->wq_trigger);
+        }
 
         return 0;
 }
@@ -391,31 +376,37 @@ static int snd_em28xx_prepare(struct snd_pcm_substream *substream)
         return 0;
 }
 
+static void audio_trigger(struct work_struct *work)
+{
+        struct em28xx *dev = container_of(work, struct em28xx, wq_trigger);
+
+        if (atomic_read(&dev->stream_started)) {
+                dprintk("starting capture");
+                em28xx_init_audio_isoc(dev);
+        } else {
+                dprintk("stopping capture");
+                em28xx_deinit_isoc_audio(dev);
+        }
+}
+
 static int snd_em28xx_capture_trigger(struct snd_pcm_substream *substream,
                                       int cmd)
 {
         struct em28xx *dev = snd_pcm_substream_chip(substream);
         int retval;
 
-        dprintk("Should %s capture\n", (cmd == SNDRV_PCM_TRIGGER_START) ?
-                                       "start" : "stop");
-
-        spin_lock(&dev->adev.slock);
         switch (cmd) {
         case SNDRV_PCM_TRIGGER_START:
-                em28xx_cmd(dev, EM28XX_CAPTURE_STREAM_EN, EM28XX_START_AUDIO);
-                retval = 0;
+                atomic_set(&dev->stream_started, 1);
                 break;
         case SNDRV_PCM_TRIGGER_STOP:
-                em28xx_cmd(dev, EM28XX_CAPTURE_STREAM_EN, EM28XX_STOP_AUDIO);
-                retval = 0;
+                atomic_set(&dev->stream_started, 1);
                 break;
         default:
                 retval = -EINVAL;
         }
-
-        spin_unlock(&dev->adev.slock);
-        return retval;
+        schedule_work(&dev->wq_trigger);
+        return 0;
 }
 
 static snd_pcm_uframes_t snd_em28xx_capture_pointer(struct snd_pcm_substream
@@ -495,6 +486,8 @@ static int em28xx_audio_init(struct em28xx *dev)
         strcpy(card->shortname, "Em28xx Audio");
         strcpy(card->longname, "Empia Em28xx Audio");
 
+        INIT_WORK(&dev->wq_trigger, audio_trigger);
+
         err = snd_card_register(card);
         if (err < 0) {
                 snd_card_free(card);
diff --git a/drivers/media/video/em28xx/em28xx.h b/drivers/media/video/em28xx/em28xx.h
index 1c61a6b65d2..adb20eb6d90 100644
--- a/drivers/media/video/em28xx/em28xx.h
+++ b/drivers/media/video/em28xx/em28xx.h
@@ -25,12 +25,13 @@
 #ifndef _EM28XX_H
 #define _EM28XX_H
 
+#include <linux/workqueue.h>
+#include <linux/i2c.h>
+#include <linux/mutex.h>
 #include <linux/videodev2.h>
+
 #include <media/videobuf-vmalloc.h>
 #include <media/v4l2-device.h>
-
-#include <linux/i2c.h>
-#include <linux/mutex.h>
 #include <media/ir-kbd-i2c.h>
 #include <media/ir-core.h>
 #if defined(CONFIG_VIDEO_EM28XX_DVB) || defined(CONFIG_VIDEO_EM28XX_DVB_MODULE)
@@ -184,11 +185,6 @@ enum em28xx_mode {
         EM28XX_DIGITAL_MODE,
 };
 
-enum em28xx_stream_state {
-        STREAM_OFF,
-        STREAM_INTERRUPT,
-        STREAM_ON,
-};
 
 struct em28xx;
 
@@ -463,7 +459,6 @@ struct em28xx_audio {
         struct snd_card            *sndcard;
 
         int users;
-        enum em28xx_stream_state capture_stream;
         spinlock_t slock;
 };
 
@@ -505,6 +500,10 @@ struct em28xx {
         unsigned int has_audio_class:1;
         unsigned int has_alsa_audio:1;
 
+        /* Controls audio streaming */
+        struct work_struct wq_trigger;              /* Trigger to start/stop audio for alsa module */
+         atomic_t       stream_started;      /* stream should be running if true */
+
         struct em28xx_fmt *format;
 
         struct em28xx_IR *ir;