From 21c27f06587d2c18150d27ca2382a509ec55c482 Mon Sep 17 00:00:00 2001 From: Saravana Kannan Date: Mon, 18 May 2020 23:30:00 -0700 Subject: driver core: Fix SYNC_STATE_ONLY device link implementation 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 Reviewed-by: Rafael J. Wysocki Link: https://lore.kernel.org/r/20200519063000.128819-1-saravanak@google.com Signed-off-by: Greg Kroah-Hartman --- drivers/base/core.c | 61 ++++++++++++++++++++++++++++++++++------------------- 1 file changed, 39 insertions(+), 22 deletions(-) (limited to 'drivers') diff --git a/drivers/base/core.c b/drivers/base/core.c index 073045cb214e..4e0e430315d9 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -360,13 +360,12 @@ 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; - } } /* @@ -433,12 +432,16 @@ 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 @@ -449,12 +452,9 @@ reorder: */ 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(); @@ -829,6 +829,13 @@ 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. @@ -842,7 +849,7 @@ 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); /* @@ -882,18 +889,35 @@ 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; @@ -903,13 +927,6 @@ 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. -- cgit v1.2.3 From 44e960490ddf868fc9135151c4a658936e771dc2 Mon Sep 17 00:00:00 2001 From: Saravana Kannan Date: Tue, 19 May 2020 21:36:26 -0700 Subject: driver core: Fix handling of SYNC_STATE_ONLY + STATELESS device links Commit 21c27f06587d ("driver core: Fix SYNC_STATE_ONLY device link implementation") didn't completely fix STATELESS + SYNC_STATE_ONLY handling. What looks like an optimization in that commit is actually a bug that causes an if condition to always take the else path. This prevents reordering of devices in the dpm_list when a DL_FLAG_STATELESS device link is create on top of an existing DL_FLAG_SYNC_STATE_ONLY device link. Fixes: 21c27f06587d ("driver core: Fix SYNC_STATE_ONLY device link implementation") Signed-off-by: Saravana Kannan Cc: stable Reviewed-by: Rafael J. Wysocki Link: https://lore.kernel.org/r/20200520043626.181820-1-saravanak@google.com Signed-off-by: Greg Kroah-Hartman --- drivers/base/core.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) (limited to 'drivers') diff --git a/drivers/base/core.c b/drivers/base/core.c index 4e0e430315d9..0cad34f1eede 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -360,12 +360,14 @@ 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 { + link->flags |= DL_FLAG_STATELESS; goto out; + } } /* -- cgit v1.2.3