Commit 8c3e315d authored May 26, 2020 by Saravana Kannan Committed by Greg Kroah-Hartman May 27, 2020

driver core: Update device link status correctly for SYNC_STATE_ONLY links

When SYNC_STATE_ONLY support was added in commit 05ef983e ("driver
core: Add device link support for SYNC_STATE_ONLY flag"),
SYNC_STATE_ONLY links were treated similar to STATELESS links in terms
of not blocking consumer probe if the supplier hasn't probed yet.

That caused a SYNC_STATE_ONLY device link's status to not get updated.
Since SYNC_STATE_ONLY device link is no longer useful once the
consumer probes, commit 21c27f06 ("driver core: Fix
SYNC_STATE_ONLY device link implementation") addresses the status
update issue by deleting the SYNC_STATE_ONLY device link instead of
complicating the status update code.

However, there are still some cases where we need to update the status
of a SYNC_STATE_ONLY device link. This is because a SYNC_STATE_ONLY
device link can later get converted into a normal MANAGED device link
when a normal MANAGED device link is created between a supplier and
consumer that already have a SYNC_STATE_ONLY device link between them.

If a SYNC_STATE_ONLY device link's status isn't maintained correctly
till it's converted to a normal MANAGED device link, then the normal
MANAGED device link will end up with a wrong link status. This can cause
a warning stack trace[1] when the consumer device probes successfully.

This commit fixes the SYNC_STATE_ONLY device link status update issue
where it wouldn't transition correctly from DL_STATE_DORMANT or
DL_STATE_AVAILABLE to DL_STATE_CONSUMER_PROBE. It also resets the status
back to DL_STATE_DORMANT or DL_STATE_AVAILABLE if the consumer probe
fails.

[1] - https://lore.kernel.org/lkml/20200522204120.3b3c9ed6@apollo/

Fixes: 05ef983e ("driver core: Add device link support for SYNC_STATE_ONLY flag")
Fixes: 21c27f06 ("driver core: Fix SYNC_STATE_ONLY device link implementation")
Reported-by: Michael Walle <michael@walle.cc>
Tested-by: Michael Walle <michael@walle.cc>
Signed-off-by: Saravana Kannan <saravanak@google.com>
Reviewed-by: Rafael J. Wysocki <rrafael.j.wysocki@intel.com>
Link: https://lore.kernel.org/r/20200526220928.49939-1-saravanak@google.com

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent c2c07616

drivers/base/core.c

+26 −8

Original line number	Diff line number	Diff line
		@@ -646,9 +646,17 @@ static void device_links_missing_supplier(struct device *dev)
		{
		struct device_link *link;

		list_for_each_entry(link, &dev->links.suppliers, c_node)
		if (link->status == DL_STATE_CONSUMER_PROBE)
		list_for_each_entry(link, &dev->links.suppliers, c_node) {
		if (link->status != DL_STATE_CONSUMER_PROBE)
		continue;

		if (link->supplier->links.status == DL_DEV_DRIVER_BOUND) {
		WRITE_ONCE(link->status, DL_STATE_AVAILABLE);
		} else {
		WARN_ON(!(link->flags & DL_FLAG_SYNC_STATE_ONLY));
		WRITE_ONCE(link->status, DL_STATE_DORMANT);
		}
		}
		}

		/**
		@@ -687,11 +695,11 @@ int device_links_check_suppliers(struct device *dev)
		device_links_write_lock();

		list_for_each_entry(link, &dev->links.suppliers, c_node) {
		if (!(link->flags & DL_FLAG_MANAGED) \|\|
		link->flags & DL_FLAG_SYNC_STATE_ONLY)
		if (!(link->flags & DL_FLAG_MANAGED))
		continue;

		if (link->status != DL_STATE_AVAILABLE) {
		if (link->status != DL_STATE_AVAILABLE &&
		!(link->flags & DL_FLAG_SYNC_STATE_ONLY)) {
		device_links_missing_supplier(dev);
		ret = -EPROBE_DEFER;
		break;
		@@ -952,11 +960,21 @@ static void __device_links_no_driver(struct device *dev)
		if (!(link->flags & DL_FLAG_MANAGED))
		continue;

		if (link->flags & DL_FLAG_AUTOREMOVE_CONSUMER)
		if (link->flags & DL_FLAG_AUTOREMOVE_CONSUMER) {
		device_link_drop_managed(link);
		else if (link->status == DL_STATE_CONSUMER_PROBE \|\|
		link->status == DL_STATE_ACTIVE)
		continue;
		}

		if (link->status != DL_STATE_CONSUMER_PROBE &&
		link->status != DL_STATE_ACTIVE)
		continue;

		if (link->supplier->links.status == DL_DEV_DRIVER_BOUND) {
		WRITE_ONCE(link->status, DL_STATE_AVAILABLE);
		} else {
		WARN_ON(!(link->flags & DL_FLAG_SYNC_STATE_ONLY));
		WRITE_ONCE(link->status, DL_STATE_DORMANT);
		}
		}

		dev->links.status = DL_DEV_NO_DRIVER;

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