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driver core: Fix SYNC_STATE_ONLY device link implementation

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When SYNC_STATE_ONLY support was added in commit 05ef983e0d ("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: 05ef983e0d ("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>
This commit is contained in:
Saravana Kannan 2020-05-18 23:30:00 -07:00 committed by Greg Kroah-Hartman
parent 2ef96a5bb1
commit 21c27f0658
1 changed files with 39 additions and 22 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

61
drivers/base/core.c
View file

@ -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 @@ 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();
@ -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.