linux-kernel - [PATCH v2 1/3] driver core: Call sync_state() even if supplier has no consumers

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Message-Id: <20200221080510.197337-2-saravanak@google.com>
Date:   Fri, 21 Feb 2020 00:05:08 -0800
From:   Saravana Kannan <saravanak@...gle.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Saravana Kannan <saravanak@...gle.com>
Cc:     kernel-team@...roid.com, linux-kernel@...r.kernel.org
Subject: [PATCH v2 1/3] driver core: Call sync_state() even if supplier has no consumers

The initial patch that added sync_state() support didn't handle the case
where a supplier has no consumers. This was because when a device is
successfully bound with a driver, only its suppliers were checked to see
if they are eligible to get a sync_state(). This is not sufficient for
devices that have no consumers but still need to do device state clean
up. So fix this.

Fixes: fc5a251d0fd7ca90 (driver core: Add sync_state driver/bus callback)
Signed-off-by: Saravana Kannan <saravanak@...gle.com>
---
 drivers/base/core.c | 23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 42a672456432..3306d5ae92a6 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -745,25 +745,31 @@ static void __device_links_queue_sync_state(struct device *dev,
 /**
  * device_links_flush_sync_list - Call sync_state() on a list of devices
  * @list: List of devices to call sync_state() on
+ * @dont_lock_dev: Device for which lock is already held by the caller
  *
  * Calls sync_state() on all the devices that have been queued for it. This
- * function is used in conjunction with __device_links_queue_sync_state().
+ * function is used in conjunction with __device_links_queue_sync_state(). The
+ * @dont_lock_dev parameter is useful when this function is called from a
+ * context where a device lock is already held.
  */
-static void device_links_flush_sync_list(struct list_head *list)
+static void device_links_flush_sync_list(struct list_head *list,
+					 struct device *dont_lock_dev)
 {
 	struct device *dev, *tmp;
 
 	list_for_each_entry_safe(dev, tmp, list, links.defer_sync) {
 		list_del_init(&dev->links.defer_sync);
 
-		device_lock(dev);
+		if (dev != dont_lock_dev)
+			device_lock(dev);
 
 		if (dev->bus->sync_state)
 			dev->bus->sync_state(dev);
 		else if (dev->driver && dev->driver->sync_state)
 			dev->driver->sync_state(dev);
 
-		device_unlock(dev);
+		if (dev != dont_lock_dev)
+			device_unlock(dev);
 
 		put_device(dev);
 	}
@@ -801,7 +807,7 @@ void device_links_supplier_sync_state_resume(void)
 out:
 	device_links_write_unlock();
 
-	device_links_flush_sync_list(&sync_list);
+	device_links_flush_sync_list(&sync_list, NULL);
 }
 
 static int sync_state_resume_initcall(void)
@@ -865,6 +871,11 @@ void device_links_driver_bound(struct device *dev)
 			driver_deferred_probe_add(link->consumer);
 	}
 
+	if (defer_sync_state_count)
+		__device_links_supplier_defer_sync(dev);
+	else
+		__device_links_queue_sync_state(dev, &sync_list);
+
 	list_for_each_entry(link, &dev->links.suppliers, c_node) {
 		if (!(link->flags & DL_FLAG_MANAGED))
 			continue;
@@ -883,7 +894,7 @@ void device_links_driver_bound(struct device *dev)
 
 	device_links_write_unlock();
 
-	device_links_flush_sync_list(&sync_list);
+	device_links_flush_sync_list(&sync_list, dev);
 }
 
 static void device_link_drop_managed(struct device_link *link)
-- 
2.25.0.265.gbab2e86ba0-goog