[PATCH v3 6/9] driver core: Replace dev->state_synced with DEV_FLAG_STATE_SYNCED

[Douglas Anderson]

In C, bitfields are not necessarily safe to modify from multiple
threads without locking. Switch "state_synced" over to the "flags"
field so modifications are safe.

Cc: Saravana Kannan <saravanak@xxxxxxxxxx>
Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
---
Not fixing any known bugs; problem is theoretical and found by code
inspection. Change is done somewhat manually and only lightly tested
(mostly compile-time tested).

Changes in v3:
- New

 drivers/base/core.c    | 9 +++++----
 drivers/base/dd.c      | 8 +++-----
 include/linux/device.h | 8 ++++----
 3 files changed, 12 insertions(+), 13 deletions(-)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index cbdfee887833..8dbb7a9c7aab 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -1123,7 +1123,7 @@ static void __device_links_queue_sync_state(struct device *dev,
 
 	if (!dev_has_sync_state(dev))
 		return;
-	if (dev->state_synced)
+	if (test_bit(DEV_FLAG_STATE_SYNCED, &dev->flags))
 		return;
 
 	list_for_each_entry(link, &dev->links.consumers, s_node) {
@@ -1138,7 +1138,7 @@ static void __device_links_queue_sync_state(struct device *dev,
 	 * than once. This can happen if new consumers get added to the device
 	 * and probed before the list is flushed.
 	 */
-	dev->state_synced = true;
+	set_bit(DEV_FLAG_STATE_SYNCED, &dev->flags);
 
 	if (WARN_ON(!list_empty(&dev->links.defer_sync)))
 		return;
@@ -1779,7 +1779,8 @@ static int fw_devlink_dev_sync_state(struct device *dev, void *data)
 	struct device *sup = link->supplier;
 
 	if (!device_link_test(link, DL_FLAG_MANAGED) ||
-	    link->status == DL_STATE_ACTIVE || sup->state_synced ||
+	    link->status == DL_STATE_ACTIVE ||
+	    test_bit(DEV_FLAG_STATE_SYNCED, &sup->flags) ||
 	    !dev_has_sync_state(sup))
 		return 0;
 
@@ -1793,7 +1794,7 @@ static int fw_devlink_dev_sync_state(struct device *dev, void *data)
 		return 0;
 
 	dev_warn(sup, "Timed out. Forcing sync_state()\n");
-	sup->state_synced = true;
+	set_bit(DEV_FLAG_STATE_SYNCED, &sup->flags);
 	get_device(sup);
 	list_add_tail(&sup->links.defer_sync, data);
 
diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 66df31696349..f5d004f919ae 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -581,12 +581,10 @@ static ssize_t state_synced_store(struct device *dev,
 		return -EINVAL;
 
 	device_lock(dev);
-	if (!dev->state_synced) {
-		dev->state_synced = true;
+	if (!test_and_set_bit(DEV_FLAG_STATE_SYNCED, &dev->flags))
 		dev_sync_state(dev);
-	} else {
+	else
 		ret = -EINVAL;
-	}
 	device_unlock(dev);
 
 	return ret ? ret : count;
@@ -598,7 +596,7 @@ static ssize_t state_synced_show(struct device *dev,
 	bool val;
 
 	device_lock(dev);
-	val = dev->state_synced;
+	val = test_bit(DEV_FLAG_STATE_SYNCED, &dev->flags);
 	device_unlock(dev);
 
 	return sysfs_emit(buf, "%u\n", val);
diff --git a/include/linux/device.h b/include/linux/device.h
index f5845bd7c3e6..6c961dac9fdb 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -477,6 +477,9 @@ struct device_physical_location {
  *		optional (if the coherent mask is large enough) also for dma
  *		allocations. This flag is managed by the dma ops instance from
  *		->dma_supported.
+ * @DEV_FLAG_STATE_SYNCED: The hardware state of this device has been synced to
+ *		match the software state of this device by calling the
+ *		driver/bus sync_state() callback.
  */
 enum struct_device_flags {
 	DEV_FLAG_READY_TO_PROBE,
@@ -484,6 +487,7 @@ enum struct_device_flags {
 	DEV_FLAG_DMA_IOMMU,
 	DEV_FLAG_DMA_SKIP_SYNC,
 	DEV_FLAG_DMA_OPS_BYPASS,
+	DEV_FLAG_STATE_SYNCED,
 };
 
 /**
@@ -565,9 +569,6 @@ enum struct_device_flags {
  * @offline:	Set after successful invocation of bus type's .offline().
  * @of_node_reused: Set if the device-tree node is shared with an ancestor
  *              device.
- * @state_synced: The hardware state of this device has been synced to match
- *		  the software state of this device by calling the driver/bus
- *		  sync_state() callback.
  * @dma_coherent: this particular device is dma coherent, even if the
  *		architecture supports non-coherent devices.
  * @flags:	DEV_FLAG_XXX flags. Use atomic bitfield operations to modify.
@@ -677,7 +678,6 @@ struct device {
 	bool			offline_disabled:1;
 	bool			offline:1;
 	bool			of_node_reused:1;
-	bool			state_synced:1;
 #if defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_DEVICE) || \
     defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU) || \
     defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU_ALL)
-- 
2.53.0.1213.gd9a14994de-goog