This commit fixes two issues:
1. The lockdep warning reported by Dong Aisheng <donga...@gmail.com> [1].
It is a warning about a cycle (dpm_list_mtx --> kn->active#3 --> fw_lock)
that was introduced when device-link devices were added to expose device
link information in sysfs.
The patch that "introduced" this cycle can't be reverted because it's fixes
a real SRCU issue and also ensures that the device-link device is deleted
as soon as the device-link is deleted. This is important to avoid sysfs
name collisions if the device-link is create again immediately (this can
happen a lot with deferred probing).
2. Inconsistency in grabbing device_pm_lock() during device link deletion
Some device link deletion code paths grab device_pm_lock(), while others
don't. The device_pm_lock() is grabbed during device_link_add() because it
checks if the supplier is in the dpm_list and also reorders the dpm_list.
However, when a device link is deleted, it does not do either of those and
therefore device_pm_lock() is not necessary. Dropping the device_pm_lock()
in all the device link deletion paths removes the inconsistency in locking.
Thanks to Stephen Boyd for helping me understand the lockdep splat.
Fixes: 843e600b8a2b ("driver core: Fix sleeping in invalid context during
device link deletion")
[1] -
https://lore.kernel.org/lkml/CAA+hA=S4eAreb7vo69LAXSk2t5=deknxhaiy1wspk4xtp9u...@mail.gmail.com/
Reported-by: Dong Aisheng <donga...@gmail.com>
Signed-off-by: Saravana Kannan <sarava...@google.com>
---
Cc'ing everyone from the original thread [1]
-Saravana
drivers/base/core.c | 4 ----
1 file changed, 4 deletions(-)
diff --git a/drivers/base/core.c b/drivers/base/core.c
index f6f620aa9408..07e5ceb40bb1 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -807,9 +807,7 @@ static void device_link_put_kref(struct device_link *link)
void device_link_del(struct device_link *link)
{
device_links_write_lock();
- device_pm_lock();
device_link_put_kref(link);
- device_pm_unlock();
device_links_write_unlock();
}
EXPORT_SYMBOL_GPL(device_link_del);
@@ -830,7 +828,6 @@ void device_link_remove(void *consumer, struct device
*supplier)
return;
device_links_write_lock();
- device_pm_lock();
list_for_each_entry(link, &supplier->links.consumers, s_node) {
if (link->consumer == consumer) {
@@ -839,7 +836,6 @@ void device_link_remove(void *consumer, struct device
*supplier)
}
}
- device_pm_unlock();
device_links_write_unlock();
}
EXPORT_SYMBOL_GPL(device_link_remove);
--
2.28.0.402.g5ffc5be6b7-goog
