On Thu, 2017-02-16 at 12:06 +0100, Peter Zijlstra wrote:

On Thu, Feb 16, 2017 at 10:01:18AM +0100, Thomas Gleixner wrote:

quoted

On Thu, 16 Feb 2017, Mike Galbraith wrote:

quoted

On Thu, 2017-02-16 at 09:37 +0100, Thomas Gleixner wrote:

quoted

On Thu, 16 Feb 2017, Mike Galbraith wrote:

...

quoted

quoted

swapvec_lock?  Oodles of 'em?  Nope.

Well, it's a per cpu lock and the lru_cache_add() variants might be called
from a gazillion of different call chains, but yes, it does not make a lot
of sense. We'll have a look.

Adding explicit local_irq_lock_init() makes things heaps better, so
presumably we need better lockdep-foo in DEFINE_LOCAL_IRQ_LOCK().

Bah.

#ifdef CONFIG_DEBUG_LOCK_ALLOC
#define PER_CPU_DEP_MAP_INIT(lockname)                          \
        .dep_map = {                                            \
                .key = ({ static struct lock_class_key __key; &__key }), \
                .name = #lockname,                              \
        }
#else
#define PER_CPU_DEP_MAP_INIT(lockname)
#endif

#define DEFINE_LOCAL_IRQ_LOCK(lvar)                             \
        DEFINE_PER_CPU(struct local_irq_lock, lvar) = {         \
                .lock = { .rlock = {                            \
                        .raw_lock = __ARCH_SPIN_LOCK_UNLOCKED,  \
                        SPIN_DEBUG_INIT(lvar)                   \
                        PER_CPU_DEP_MAP_INIT(lvar)              \
                } }                                             \
        }

That's fairly horrible for poking inside all the internals, but it might
just work ;-

Weeell, I'm trying to cobble something kinda like that together using
__RT_SPIN_INITIALIZER() instead, but seems mean ole Mr. Compiler NAKs
the PER_CPU_DEP_MAP_INIT() thingy.

  CC      mm/swap.o
mm/swap.c:54:689: error: braced-group within expression allowed only
inside a function

	-Mike