[ 80/86] dca: check against empty dca_domains list before unregister provider

[Greg Kroah-Hartman]

3.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Maciej Sosnowski <maciej.sosnowski@xxxxxxxxx>

commit c419fcfd071cf34ba00f9f65282583772d2655e7 upstream.

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 <jiang.liu@xxxxxxxxxx>
Tested-by: Gaohuai Han <hangaohuai@xxxxxxxxxx>
Signed-off-by: Maciej Sosnowski <maciej.sosnowski@xxxxxxxxx>
Signed-off-by: Dan Williams <djbw@xxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

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

--- 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);


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