[PATCH v1 3/3] PM: sleep: Fix possible deadlocks in core system-wide PM code

["Rafael J. Wysocki" <rjw@rjwysocki.net>]

From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

It is reported that in low-memory situations the system-wide resume core
code deadlocks, because async_schedule_dev() executes its argument
function synchronously if it cannot allocate memory (an not only then)
and that function attempts to acquire a mutex that is already held.

Address this by changing the code in question to use
async_schedule_dev_nocall() for scheduling the asynchronous
execution of device suspend and resume functions and to directly
run them synchronously if async_schedule_dev_nocall() returns false.

Fixes: 09beebd8f93b ("PM: sleep: core: Switch back to async_schedule_dev()")
Link: https://lore.kernel.org/linux-pm/ZYvjiqX6EsL15moe@perf/
Reported-by: Youngmin Nam <youngmin.nam@samsung.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---

The commit pointed to by the Fixes: tag is the last one that modified
the code in question, even though the bug had been there already before.

Still, the fix will not apply to the code before that commit.

---
 drivers/base/power/main.c |  148 +++++++++++++++++++++-------------------------
 1 file changed, 68 insertions(+), 80 deletions(-)

Index: linux-pm/drivers/base/power/main.c
===================================================================
--- linux-pm.orig/drivers/base/power/main.c
+++ linux-pm/drivers/base/power/main.c
@@ -579,7 +579,7 @@ bool dev_pm_skip_resume(struct device *d
 }
 
 /**
- * device_resume_noirq - Execute a "noirq resume" callback for given device.
+ * __device_resume_noirq - Execute a "noirq resume" callback for given device.
  * @dev: Device to handle.
  * @state: PM transition of the system being carried out.
  * @async: If true, the device is being resumed asynchronously.
@@ -587,7 +587,7 @@ bool dev_pm_skip_resume(struct device *d
  * The driver of @dev will not receive interrupts while this function is being
  * executed.
  */
-static int device_resume_noirq(struct device *dev, pm_message_t state, bool async)
+static void __device_resume_noirq(struct device *dev, pm_message_t state, bool async)
 {
 	pm_callback_t callback = NULL;
 	const char *info = NULL;
@@ -655,7 +655,13 @@ Skip:
 Out:
 	complete_all(&dev->power.completion);
 	TRACE_RESUME(error);
-	return error;
+
+	if (error) {
+		suspend_stats.failed_resume_noirq++;
+		dpm_save_failed_step(SUSPEND_RESUME_NOIRQ);
+		dpm_save_failed_dev(dev_name(dev));
+		pm_dev_err(dev, state, async ? " async noirq" : " noirq", error);
+	}
 }
 
 static bool is_async(struct device *dev)
@@ -668,11 +674,15 @@ static bool dpm_async_fn(struct device *
 {
 	reinit_completion(&dev->power.completion);
 
-	if (is_async(dev)) {
-		get_device(dev);
-		async_schedule_dev(func, dev);
+	if (!is_async(dev))
+		return false;
+
+	get_device(dev);
+
+	if (async_schedule_dev_nocall(func, dev))
 		return true;
-	}
+
+	put_device(dev);
 
 	return false;
 }
@@ -680,15 +690,19 @@ static bool dpm_async_fn(struct device *
 static void async_resume_noirq(void *data, async_cookie_t cookie)
 {
 	struct device *dev = data;
-	int error;
-
-	error = device_resume_noirq(dev, pm_transition, true);
-	if (error)
-		pm_dev_err(dev, pm_transition, " async", error);
 
+	__device_resume_noirq(dev, pm_transition, true);
 	put_device(dev);
 }
 
+static void device_resume_noirq(struct device *dev)
+{
+	if (dpm_async_fn(dev, async_resume_noirq))
+		return;
+
+	__device_resume_noirq(dev, pm_transition, false);
+}
+
 static void dpm_noirq_resume_devices(pm_message_t state)
 {
 	struct device *dev;
@@ -698,14 +712,6 @@ static void dpm_noirq_resume_devices(pm_
 	mutex_lock(&dpm_list_mtx);
 	pm_transition = state;
 
-	/*
-	 * Advanced the async threads upfront,
-	 * in case the starting of async threads is
-	 * delayed by non-async resuming devices.
-	 */
-	list_for_each_entry(dev, &dpm_noirq_list, power.entry)
-		dpm_async_fn(dev, async_resume_noirq);
-
 	while (!list_empty(&dpm_noirq_list)) {
 		dev = to_device(dpm_noirq_list.next);
 		get_device(dev);
@@ -713,17 +719,7 @@ static void dpm_noirq_resume_devices(pm_
 
 		mutex_unlock(&dpm_list_mtx);
 
-		if (!is_async(dev)) {
-			int error;
-
-			error = device_resume_noirq(dev, state, false);
-			if (error) {
-				suspend_stats.failed_resume_noirq++;
-				dpm_save_failed_step(SUSPEND_RESUME_NOIRQ);
-				dpm_save_failed_dev(dev_name(dev));
-				pm_dev_err(dev, state, " noirq", error);
-			}
-		}
+		device_resume_noirq(dev);
 
 		put_device(dev);
 
@@ -751,14 +747,14 @@ void dpm_resume_noirq(pm_message_t state
 }
 
 /**
- * device_resume_early - Execute an "early resume" callback for given device.
+ * __device_resume_early - Execute an "early resume" callback for given device.
  * @dev: Device to handle.
  * @state: PM transition of the system being carried out.
  * @async: If true, the device is being resumed asynchronously.
  *
  * Runtime PM is disabled for @dev while this function is being executed.
  */
-static int device_resume_early(struct device *dev, pm_message_t state, bool async)
+static void __device_resume_early(struct device *dev, pm_message_t state, bool async)
 {
 	pm_callback_t callback = NULL;
 	const char *info = NULL;
@@ -811,21 +807,31 @@ Out:
 
 	pm_runtime_enable(dev);
 	complete_all(&dev->power.completion);
-	return error;
+
+	if (error) {
+		suspend_stats.failed_resume_early++;
+		dpm_save_failed_step(SUSPEND_RESUME_EARLY);
+		dpm_save_failed_dev(dev_name(dev));
+		pm_dev_err(dev, state, async ? " async early" : " early", error);
+	}
 }
 
 static void async_resume_early(void *data, async_cookie_t cookie)
 {
 	struct device *dev = data;
-	int error;
-
-	error = device_resume_early(dev, pm_transition, true);
-	if (error)
-		pm_dev_err(dev, pm_transition, " async", error);
 
+	__device_resume_early(dev, pm_transition, true);
 	put_device(dev);
 }
 
+static void device_resume_early(struct device *dev)
+{
+	if (dpm_async_fn(dev, async_resume_early))
+		return;
+
+	__device_resume_early(dev, pm_transition, false);
+}
+
 /**
  * dpm_resume_early - Execute "early resume" callbacks for all devices.
  * @state: PM transition of the system being carried out.
@@ -839,14 +845,6 @@ void dpm_resume_early(pm_message_t state
 	mutex_lock(&dpm_list_mtx);
 	pm_transition = state;
 
-	/*
-	 * Advanced the async threads upfront,
-	 * in case the starting of async threads is
-	 * delayed by non-async resuming devices.
-	 */
-	list_for_each_entry(dev, &dpm_late_early_list, power.entry)
-		dpm_async_fn(dev, async_resume_early);
-
 	while (!list_empty(&dpm_late_early_list)) {
 		dev = to_device(dpm_late_early_list.next);
 		get_device(dev);
@@ -854,17 +852,7 @@ void dpm_resume_early(pm_message_t state
 
 		mutex_unlock(&dpm_list_mtx);
 
-		if (!is_async(dev)) {
-			int error;
-
-			error = device_resume_early(dev, state, false);
-			if (error) {
-				suspend_stats.failed_resume_early++;
-				dpm_save_failed_step(SUSPEND_RESUME_EARLY);
-				dpm_save_failed_dev(dev_name(dev));
-				pm_dev_err(dev, state, " early", error);
-			}
-		}
+		device_resume_early(dev);
 
 		put_device(dev);
 
@@ -888,12 +876,12 @@ void dpm_resume_start(pm_message_t state
 EXPORT_SYMBOL_GPL(dpm_resume_start);
 
 /**
- * device_resume - Execute "resume" callbacks for given device.
+ * __device_resume - Execute "resume" callbacks for given device.
  * @dev: Device to handle.
  * @state: PM transition of the system being carried out.
  * @async: If true, the device is being resumed asynchronously.
  */
-static int device_resume(struct device *dev, pm_message_t state, bool async)
+static void __device_resume(struct device *dev, pm_message_t state, bool async)
 {
 	pm_callback_t callback = NULL;
 	const char *info = NULL;
@@ -975,20 +963,30 @@ static int device_resume(struct device *
 
 	TRACE_RESUME(error);
 
-	return error;
+	if (error) {
+		suspend_stats.failed_resume++;
+		dpm_save_failed_step(SUSPEND_RESUME);
+		dpm_save_failed_dev(dev_name(dev));
+		pm_dev_err(dev, state, async ? " async" : "", error);
+	}
 }
 
 static void async_resume(void *data, async_cookie_t cookie)
 {
 	struct device *dev = data;
-	int error;
 
-	error = device_resume(dev, pm_transition, true);
-	if (error)
-		pm_dev_err(dev, pm_transition, " async", error);
+	__device_resume(dev, pm_transition, true);
 	put_device(dev);
 }
 
+static void device_resume(struct device *dev)
+{
+	if (dpm_async_fn(dev, async_resume))
+		return;
+
+	__device_resume(dev, pm_transition, false);
+}
+
 /**
  * dpm_resume - Execute "resume" callbacks for non-sysdev devices.
  * @state: PM transition of the system being carried out.
@@ -1008,27 +1006,17 @@ void dpm_resume(pm_message_t state)
 	pm_transition = state;
 	async_error = 0;
 
-	list_for_each_entry(dev, &dpm_suspended_list, power.entry)
-		dpm_async_fn(dev, async_resume);
-
 	while (!list_empty(&dpm_suspended_list)) {
 		dev = to_device(dpm_suspended_list.next);
+
 		get_device(dev);
-		if (!is_async(dev)) {
-			int error;
 
-			mutex_unlock(&dpm_list_mtx);
+		mutex_unlock(&dpm_list_mtx);
 
-			error = device_resume(dev, state, false);
-			if (error) {
-				suspend_stats.failed_resume++;
-				dpm_save_failed_step(SUSPEND_RESUME);
-				dpm_save_failed_dev(dev_name(dev));
-				pm_dev_err(dev, state, "", error);
-			}
+		device_resume(dev);
+
+		mutex_lock(&dpm_list_mtx);
 
-			mutex_lock(&dpm_list_mtx);
-		}
 		if (!list_empty(&dev->power.entry))
 			list_move_tail(&dev->power.entry, &dpm_prepared_list);