ALSA: hda: Fix racy display power access

snd_hdac_display_power() doesn't handle the concurrent calls carefully enough, and it may lead to the doubly get_power or put_power calls, when a runtime PM and an async work get called in racy way. This patch addresses it by reusing the bus->lock mutex that has been used for protecting the link state change in ext bus code, so that it can protect against racy display state changes. The initialization of bus->lock was moved from snd_hdac_ext_bus_init() to snd_hdac_bus_init() as well accordingly. Testcase: igt/i915_pm_rpm/module-reload #glk-dsi Reported-by: Chris Wilson <[email protected]> Reviewed-by: Chris Wilson <[email protected]> Cc: Imre Deak <[email protected]> Signed-off-by: Takashi Iwai <[email protected]>
josf · Apr 10, 2019 · d7a181d · d7a181d
1 parent cae3052
commit d7a181d
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Showing 3 changed files with 6 additions and 2 deletions.
diff --git a/sound/hda/ext/hdac_ext_bus.c b/sound/hda/ext/hdac_ext_bus.c
@@ -107,7 +107,6 @@ int snd_hdac_ext_bus_init(struct hdac_bus *bus, struct device *dev,
 	INIT_LIST_HEAD(&bus->hlink_list);
 	bus->idx = idx++;
 
-	mutex_init(&bus->lock);
 	bus->cmd_dma_state = true;
 
 	return 0;

diff --git a/sound/hda/hdac_bus.c b/sound/hda/hdac_bus.c
@@ -38,6 +38,7 @@ int snd_hdac_bus_init(struct hdac_bus *bus, struct device *dev,
 	INIT_WORK(&bus->unsol_work, snd_hdac_bus_process_unsol_events);
 	spin_lock_init(&bus->reg_lock);
 	mutex_init(&bus->cmd_mutex);
+	mutex_init(&bus->lock);
 	bus->irq = -1;
 	return 0;
 }

diff --git a/sound/hda/hdac_component.c b/sound/hda/hdac_component.c
@@ -69,13 +69,15 @@ void snd_hdac_display_power(struct hdac_bus *bus, unsigned int idx, bool enable)
 
 	dev_dbg(bus->dev, "display power %s\n",
 		enable ? "enable" : "disable");
+
+	mutex_lock(&bus->lock);
 	if (enable)
 		set_bit(idx, &bus->display_power_status);
 	else
 		clear_bit(idx, &bus->display_power_status);
 
 	if (!acomp || !acomp->ops)
-		return;
+		goto unlock;
 
 	if (bus->display_power_status) {
 		if (!bus->display_power_active) {
@@ -92,6 +94,8 @@ void snd_hdac_display_power(struct hdac_bus *bus, unsigned int idx, bool enable)
 			bus->display_power_active = false;
 		}
 	}
+ unlock:
+	mutex_unlock(&bus->lock);
 }
 EXPORT_SYMBOL_GPL(snd_hdac_display_power);