acpi: bus: check once more for an empty list after locking it

List could have become empty after the unlocked check that was made earlier,
so check again inside the lock.

Should fix https://bugzilla.redhat.com/show_bug.cgi?id=427765

Signed-off-by: Chuck Ebbert <cebbert@redhat.com>
Cc: <stable@kernel.org>
Cc: Len Brown <lenb@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/acpi/bus.c b/drivers/acpi/bus.c
index 5b6760e..2d1955c 100644 (file)
--- a/drivers/acpi/bus.c
+++ b/drivers/acpi/bus.c
@@ -373,10 +373,11 @@ int acpi_bus_receive_event(struct acpi_bus_event *event)
        }
 
        spin_lock_irqsave(&acpi_bus_event_lock, flags);
-       entry =
-           list_entry(acpi_bus_event_list.next, struct acpi_bus_event, node);
-       if (entry)
+       if (!list_empty(&acpi_bus_event_list)) {
+               entry = list_entry(acpi_bus_event_list.next,
+                                  struct acpi_bus_event, node);
                list_del(&entry->node);
+       }
        spin_unlock_irqrestore(&acpi_bus_event_lock, flags);
 
        if (!entry)