sync: rvck #312: 【Backport】ACPI模式下的启动时序修复

drivers/acpi/scan.c

@@ -5,6 +5,7 @@
 
 #define pr_fmt(fmt) "ACPI: " fmt
 
+#include <linux/async.h>
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/slab.h>
@@ -2358,46 +2359,34 @@ static int acpi_dev_get_next_consumer_dev_cb(struct acpi_dep_data *dep, void *da
 	return 0;
 }
 
-struct acpi_scan_clear_dep_work {
-	struct work_struct work;
-	struct acpi_device *adev;
-};
-
-static void acpi_scan_clear_dep_fn(struct work_struct *work)
+static void acpi_scan_clear_dep_fn(void *dev, async_cookie_t cookie)
 {
-	struct acpi_scan_clear_dep_work *cdw;
-
-	cdw = container_of(work, struct acpi_scan_clear_dep_work, work);
+	struct acpi_device *adev = to_acpi_device(dev);
 
 	acpi_scan_lock_acquire();
-	acpi_bus_attach(cdw->adev, (void *)true);
+	acpi_bus_attach(adev, (void *)true);
 	acpi_scan_lock_release();
 
-	acpi_dev_put(cdw->adev);
-	kfree(cdw);
+	acpi_dev_put(adev);
 }
 
 static bool acpi_scan_clear_dep_queue(struct acpi_device *adev)
 {
-	struct acpi_scan_clear_dep_work *cdw;
-
 	if (adev->dep_unmet)
 		return false;
 
-	cdw = kmalloc(sizeof(*cdw), GFP_KERNEL);
-	if (!cdw)
-		return false;
-
-	cdw->adev = adev;
-	INIT_WORK(&cdw->work, acpi_scan_clear_dep_fn);
 	/*
-	 * Since the work function may block on the lock until the entire
-	 * initial enumeration of devices is complete, put it into the unbound
-	 * workqueue.
+	 * Async schedule the deferred acpi_scan_clear_dep_fn() since:
+	 * - acpi_bus_attach() needs to hold acpi_scan_lock which cannot
+	 *   be acquired under acpi_dep_list_lock (held here)
+	 * - the deferred work at boot stage is ensured to be finished
+	 *   before userspace init task by the async_synchronize_full()
+	 *   barrier
+	 *
+	 * Use _nocall variant since it'll return on failure instead of
+	 * run the function synchronously.
 	 */
-	queue_work(system_unbound_wq, &cdw->work);
-
-	return true;
+	return async_schedule_dev_nocall(acpi_scan_clear_dep_fn, &adev->dev);
 }
 
 static void acpi_scan_delete_dep_data(struct acpi_dep_data *dep)