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Subject[PATCH] hpilo: add locking comment
Add explanation about lock nesting and purpose of each lock in hpilo.

This applies on top of a set of patches I sent out to add polling to hpilo.

Please CC me on any replies, and thanks,
Dave

Signed-off-by: David Altobelli <david.altobelli@hp.com>
---
--- linux-2.6.30.3/drivers/misc/hpilo.h.orig 2009-08-19 10:38:23.000000000 -0500
+++ linux-2.6.30.3/drivers/misc/hpilo.h 2009-08-19 11:06:36.000000000 -0500
@@ -44,9 +44,20 @@ struct ilo_hwinfo {

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;
};

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