Re: hashed spinlocks

["David S. Miller" <davem@davemloft.net>]

From: Daniel Walker <dwalker@mvista.com>
Date: Sun, 31 Jul 2005 12:06:47 -0700

> The ifdef that switched between the two rt_hash_lock_addr() switched on
> for CONFIG_SMP or CONFIG_DEBUG_SPINLOCK . I was compiling UP , so I
> didn't get either.
> 
> Seems like you'll need to have an rt_hash_lock(slot) that replaces the
> spin_lock calls ..

spin_lock(x) and spin_unlock(x) are both a nop in this case, so what
is the problem passing in a NULL?  The argument is arbitrary and should
should just ignored, right?

If both CONFIG_SMP and CONFIG_DEBUG_SPINLOCK are disabled, we
end up with these definitions in linux/spinlock.h

#define spin_lock(lock)		_spin_lock(lock)

#define _spin_lock(lock)	\
do { \
	preempt_disable(); \
	_raw_spin_lock(lock); \
	__acquire(lock); \
} while(0)

#define _raw_spin_lock(lock)	do { (void)(lock); } while(0)

What kind of warning do you get?