When SYNC_STATE_ONLY support was added in commit 05ef983e0d65 ("driver core: Add device link support for SYNC_STATE_ONLY flag"), device_link_add() incorrectly skipped adding the new SYNC_STATE_ONLY device link to the supplier's and consumer's "device link" list.
This causes multiple issues: - The device link is lost forever from driver core if the caller didn't keep track of it (caller typically isn't expected to). This is a memory leak. - The device link is also never visible to any other code path after device_link_add() returns.
If we fix the "device link" list handling, that exposes a bunch of issues.
1. The device link "status" state management code rightfully doesn't handle the case where a DL_FLAG_MANAGED device link exists between a supplier and consumer, but the consumer manages to probe successfully before the supplier. The addition of DL_FLAG_SYNC_STATE_ONLY links break this assumption. This causes device_links_driver_bound() to throw a warning when this happens.
Since DL_FLAG_SYNC_STATE_ONLY device links are mainly used for creating proxy device links for child device dependencies and aren't useful once the consumer device probes successfully, this patch just deletes DL_FLAG_SYNC_STATE_ONLY device links once its consumer device probes. This way, we avoid the warning, free up some memory and avoid complicating the device links "status" state management code.
2. Creating a DL_FLAG_STATELESS device link between two devices that already have a DL_FLAG_SYNC_STATE_ONLY device link will result in the DL_FLAG_STATELESS flag not getting set correctly. This patch also fixes this.
Lastly, this patch also fixes minor whitespace issues.
Cc: stable@vger.kernel.org Fixes: 05ef983e0d65 ("driver core: Add device link support for SYNC_STATE_ONLY flag") Signed-off-by: Saravana Kannan saravanak@google.com --- v3: - Added this changelog text v2: - Delete DL_FLAG_SYNC_STATE_ONLY device links on consumer probe - Set DL_FLAG_STATELESS correct when added to an existing DL_FLAG_SYNC_STATE_ONLY device link. v1: - Add device link to list - Minor whitespace fixes
drivers/base/core.c | 61 +++++++++++++++++++++++++++++---------------- 1 file changed, 39 insertions(+), 22 deletions(-)
diff --git a/drivers/base/core.c b/drivers/base/core.c index 84c569726d75..f804e561e0a2 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -363,13 +363,12 @@ struct device_link *device_link_add(struct device *consumer,
if (flags & DL_FLAG_STATELESS) { kref_get(&link->kref); + link->flags |= DL_FLAG_STATELESS; if (link->flags & DL_FLAG_SYNC_STATE_ONLY && - !(link->flags & DL_FLAG_STATELESS)) { - link->flags |= DL_FLAG_STATELESS; + !(link->flags & DL_FLAG_STATELESS)) goto reorder; - } else { + else goto out; - } }
/* @@ -436,12 +435,16 @@ struct device_link *device_link_add(struct device *consumer, flags & DL_FLAG_PM_RUNTIME) pm_runtime_resume(supplier);
+ list_add_tail_rcu(&link->s_node, &supplier->links.consumers); + list_add_tail_rcu(&link->c_node, &consumer->links.suppliers); + if (flags & DL_FLAG_SYNC_STATE_ONLY) { dev_dbg(consumer, "Linked as a sync state only consumer to %s\n", dev_name(supplier)); goto out; } + reorder: /* * Move the consumer and all of the devices depending on it to the end @@ -452,12 +455,9 @@ struct device_link *device_link_add(struct device *consumer, */ device_reorder_to_tail(consumer, NULL);
- list_add_tail_rcu(&link->s_node, &supplier->links.consumers); - list_add_tail_rcu(&link->c_node, &consumer->links.suppliers); - dev_dbg(consumer, "Linked as a consumer to %s\n", dev_name(supplier));
- out: +out: device_pm_unlock(); device_links_write_unlock();
@@ -832,6 +832,13 @@ static void __device_links_supplier_defer_sync(struct device *sup) list_add_tail(&sup->links.defer_sync, &deferred_sync); }
+static void device_link_drop_managed(struct device_link *link) +{ + link->flags &= ~DL_FLAG_MANAGED; + WRITE_ONCE(link->status, DL_STATE_NONE); + kref_put(&link->kref, __device_link_del); +} + /** * device_links_driver_bound - Update device links after probing its driver. * @dev: Device to update the links for. @@ -845,7 +852,7 @@ static void __device_links_supplier_defer_sync(struct device *sup) */ void device_links_driver_bound(struct device *dev) { - struct device_link *link; + struct device_link *link, *ln; LIST_HEAD(sync_list);
/* @@ -885,18 +892,35 @@ void device_links_driver_bound(struct device *dev) else __device_links_queue_sync_state(dev, &sync_list);
- list_for_each_entry(link, &dev->links.suppliers, c_node) { + list_for_each_entry_safe(link, ln, &dev->links.suppliers, c_node) { + struct device *supplier; + if (!(link->flags & DL_FLAG_MANAGED)) continue;
- WARN_ON(link->status != DL_STATE_CONSUMER_PROBE); - WRITE_ONCE(link->status, DL_STATE_ACTIVE); + supplier = link->supplier; + if (link->flags & DL_FLAG_SYNC_STATE_ONLY) { + /* + * When DL_FLAG_SYNC_STATE_ONLY is set, it means no + * other DL_MANAGED_LINK_FLAGS have been set. So, it's + * save to drop the managed link completely. + */ + device_link_drop_managed(link); + } else { + WARN_ON(link->status != DL_STATE_CONSUMER_PROBE); + WRITE_ONCE(link->status, DL_STATE_ACTIVE); + }
+ /* + * This needs to be done even for the deleted + * DL_FLAG_SYNC_STATE_ONLY device link in case it was the last + * device link that was preventing the supplier from getting a + * sync_state() call. + */ if (defer_sync_state_count) - __device_links_supplier_defer_sync(link->supplier); + __device_links_supplier_defer_sync(supplier); else - __device_links_queue_sync_state(link->supplier, - &sync_list); + __device_links_queue_sync_state(supplier, &sync_list); }
dev->links.status = DL_DEV_DRIVER_BOUND; @@ -906,13 +930,6 @@ void device_links_driver_bound(struct device *dev) device_links_flush_sync_list(&sync_list, dev); }
-static void device_link_drop_managed(struct device_link *link) -{ - link->flags &= ~DL_FLAG_MANAGED; - WRITE_ONCE(link->status, DL_STATE_NONE); - kref_put(&link->kref, __device_link_del); -} - /** * __device_links_no_driver - Update links of a device without a driver. * @dev: Device without a drvier.