0943d6
(x86, ticketlock: Clean up types and accessors) which reduced the size
of arch_spinlock_t.

Fix this by making xl->spinners a u8 if NR_CPUS < 256.  A
BUILD_BUG_ON() is also added to check the sizes of the two structures
are compatible.

In many cases this was not noticable as there would often be padding
bytes after the lock (e.g., if any of CONFIG_GENERIC_LOCKBREAK,
CONFIG_DEBUG_SPINLOCK, or CONFIG_DEBUG_LOCK_ALLOC were enabled).

The bnx2 driver is affected. In struct bnx2, phy_lock and
indirect_lock may have no padding after them.  Contention on phy_lock
would corrupt indirect_lock making it appear locked and the driver
would deadlock.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy@goop.org>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
CC: stable@kernel.org #only 3.2
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
“Ü