On Wed, Jul 23, 2008 at 12:59:21AM -0700, David Miller wrote:

From: Jarek Poplawski <redacted>
Date: Wed, 23 Jul 2008 06:20:36 +0000

quoted

PS: if there is nothing new in lockdep the classical method would
be to change this static array:

static struct lock_class_key
netdev_xmit_lock_key[ARRAY_SIZE(netdev_lock_type)];

to

static struct lock_class_key
netdev_xmit_lock_key[ARRAY_SIZE(netdev_lock_type)][MAX_NUM_TX_QUEUES];

and set lockdep classes per queue as well. (If we are sure we don't
need lockdep subclasses anywhere this could be optimized by using
one lock_class_key per 8 queues and spin_lock_nested()).

Unfortunately MAX_NUM_TX_QUEUES is USHORT_MAX, so this isn't really
a feasible approach.

Is it used by real devices already? Maybe for the beginning we could
start with something less?

spin_lock_nested() isn't all that viable either, as the subclass
limit is something like 8.

This method would need to do some additional counting: depending of
a queue number each 8 subsequent queues share (are set to) the same
class and their number mod 8 gives the subqueue number for
spin_lock_nested().

I'll try to find if there is something new around this in lockdep.
(lockdep people added to CC.)

Jarek P.
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