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authorSaravana Kannan <saravanak@google.com>2020-05-19 09:30:00 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2020-05-19 18:01:58 +0300
commit21c27f06587d2c18150d27ca2382a509ec55c482 (patch)
treecc19a443a1b12aec7a727559923b570a54a012af /drivers/base
parent2ef96a5bb12be62ef75b5828c0aab838ebb29cb8 (diff)
downloadlinux-21c27f06587d2c18150d27ca2382a509ec55c482.tar.xz
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 <saravanak@google.com> Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Link: https://lore.kernel.org/r/20200519063000.128819-1-saravanak@google.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/base')
-rw-r--r--drivers/base/core.c61
1 files changed, 39 insertions, 22 deletions
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.