hpilo: add locking comment
Add explanation about lock nesting and purpose of each lock in hpilo.
Signed-off-by: David Altobelli <david.altobelli@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/misc/hpilo.h b/drivers/misc/hpilo.h
index 3857605..247eb38 100644
--- a/drivers/misc/hpilo.h
+++ b/drivers/misc/hpilo.h
@@ -44,9 +44,20 @@
struct pci_dev *ilo_dev;
+ /*
+ * open_lock serializes ccb_cnt during open and close
+ * [ irq disabled ]
+ * -> alloc_lock used when adding/removing/searching ccb_alloc,
+ * which represents all ccbs open on the device
+ * --> fifo_lock controls access to fifo queues shared with hw
+ *
+ * Locks must be taken in this order, but open_lock and alloc_lock
+ * are optional, they do not need to be held in order to take a
+ * lower level lock.
+ */
+ spinlock_t open_lock;
spinlock_t alloc_lock;
spinlock_t fifo_lock;
- spinlock_t open_lock;
struct cdev cdev;
};