[PATCH] dca: check against empty dca_domains list before unregister provider

When providers get blocked unregister_dca_providers() is called ending up
with dca_providers and dca_domain lists emptied. Dca should be prevented from
trying to unregister any provider if dca_domain list is found empty.

Reported-by: Jiang Liu <redacted>
Tested-by: Gaohuai Han <redacted>
Signed-off-by: Maciej Sosnowski <redacted>
---

 drivers/dca/dca-core.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/drivers/dca/dca-core.c b/drivers/dca/dca-core.c
index bc6f5fa..819dfda 100644
--- a/drivers/dca/dca-core.c
+++ b/drivers/dca/dca-core.c

@@ -420,6 +420,11 @@ void unregister_dca_provider(struct dca_
 
 	raw_spin_lock_irqsave(&dca_lock, flags);
 
+	if (list_empty(&dca_domains)) {
+		raw_spin_unlock_irqrestore(&dca_lock, flags);
+		return;
+	}
+
 	list_del(&dca->node);
 
 	pci_rc = dca_pci_rc_from_dev(dev);