driver core: Update device link status correctly for SYNC_STATE_ONLY links

When SYNC_STATE_ONLY support was added in commit 05ef983e0d65 ("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 21c27f06587d ("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: 05ef983e0d65 ("driver core: Add device link support for SYNC_STATE_ONLY flag")
Fixes: 21c27f06587d ("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>

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 791b753..9a76dd4 100644 (file)
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -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;