When releasing a device, if the release action causes a group to be
released, a warning is emitted because it can't find the group. This
happens because devres_release_all() moves the entire list to a todo
list and also move the group markers. Considering r* normal resource
nodes and g1 a group resource node:
g1 -----------.
v v
r1 -> r2 -> g1[0] -> r3-> g[1] -> r4
After devres_release_all(), dev->devres_head becomes empty and the todo
list it iterates on becomes:
g1
v
r1 -> r2 -> r3-> r4 -> g1[0]
When a call to component_del() is made and takes down the aggregate
device, a warning like this happen:
RIP: 0010:devres_release_group+0x362/0x530
...
Call Trace:
<TASK>
component_unbind+0x156/0x380
component_unbind_all+0x1d0/0x270
mei_component_master_unbind+0x28/0x80 [mei_hdcp]
take_down_aggregate_device+0xc1/0x160
component_del+0x1c6/0x3e0
intel_hdcp_component_fini+0xf1/0x170 [xe]
xe_display_fini+0x1e/0x40 [xe]
Because the devres group corresponding to the hdcp component cannot be
found. Just ignore this corner case: if the dev->devres_head is empty
and the caller is trying to remove a group, it's likely in the process
of device cleanup so just ignore it instead of warning.
Signed-off-by: Lucas De Marchi <lucas.demarchi@xxxxxxxxx>
---
The check for just an empty devres_head seems simple and sufficient,
although the caller of devres_release_group() can still shoot its own
foot. I thought about a flag on dev to check it's being removed, but I
want to know others' opinions first.
drivers/base/devres.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/drivers/base/devres.c b/drivers/base/devres.c
index 93e7779ef21e8..b955a2f9520bf 100644
--- a/drivers/base/devres.c
+++ b/drivers/base/devres.c
@@ -687,6 +687,13 @@ int devres_release_group(struct device *dev, void *id)
spin_unlock_irqrestore(&dev->devres_lock, flags);
release_nodes(dev, &todo);
+ } else if (list_empty(&dev->devres_head)) {
+ /*
+ * dev is probably dying via devres_release_all(): groups
+ * have already been removed and are on the process of
+ * being released - don't touch and don't warn.
+ */
+ spin_unlock_irqrestore(&dev->devres_lock, flags);
} else {
WARN_ON(1);
spin_unlock_irqrestore(&dev->devres_lock, flags);
--
2.48.1
