ALSA: hda - Fix another race in runtime PM refcounting

Although some races in runtime PM refcount was fixed by the commit
[664c715573c2: ALSA: hda - Work around races of power up/down with
runtime PM], there is still a race in the following case:

CPU0:                   CPU1 :
runtime suspend:
  codec->in_pm = 1
                        snd_hdac_power_up_pm():
                          pm_runtime_get_sync() skipped
suspend finished:
  codec->in_pm = 0
                        snd_hdac_power_down_pm():
                          pm_runtime_put_*() is called!

For avoiding this situation, increment in_pm flag atomically when it's
non-zero, and decrement accordingly, to ensure that in_pm is set
consistently for the whole concurrent operations.

Also, since atomic_inc_not_zero() and atomic_dec_if_positive() are
lengthy inline functions, move snd_hdac_power_up_pm() and _down_pm()
to sound/hda/hdac_device.c as no inline functions.

Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 30 insertions, 0 deletions

diff --git a/sound/hda/hdac_device.c b/sound/hda/hdac_device.c
index 92604bbcee5f..f75bf5622687 100644
--- a/sound/hda/hdac_device.c
+++ b/sound/hda/hdac_device.c
@@ -519,6 +519,36 @@ void snd_hdac_power_down(struct hdac_device *codec)
         pm_runtime_put_autosuspend(dev);
 }
 EXPORT_SYMBOL_GPL(snd_hdac_power_down);
+
+/**
+ * snd_hdac_power_up_pm - power up the codec
+ * @codec: the codec object
+ *
+ * This function can be called in a recursive code path like init code
+ * which may be called by PM suspend/resume again.  OTOH, if a power-up
+ * call must wake up the sleeper (e.g. in a kctl callback), use
+ * snd_hdac_power_up() instead.
+ */
+void snd_hdac_power_up_pm(struct hdac_device *codec)
+{
+        if (!atomic_inc_not_zero(&codec->in_pm))
+                snd_hdac_power_up(codec);
+}
+EXPORT_SYMBOL_GPL(snd_hdac_power_up_pm);
+
+/**
+ * snd_hdac_power_down_pm - power down the codec
+ * @codec: the codec object
+ *
+ * Like snd_hdac_power_up_pm(), this function is used in a recursive
+ * code path like init code which may be called by PM suspend/resume again.
+ */
+void snd_hdac_power_down_pm(struct hdac_device *codec)
+{
+        if (atomic_dec_if_positive(&codec->in_pm) < 0)
+                snd_hdac_power_down(codec);
+}
+EXPORT_SYMBOL_GPL(snd_hdac_power_down_pm);
 #endif
 
 /* codec vendor labels */