Re: [RT] lockdep munching nr_list_entries like popcorn

Mike Galbraith
2017-02-16T14:42:59Z

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:
> > On Thu, 16 Feb 2017, Mike Galbraith wrote:
> >
> > > On Thu, 2017-02-16 at 09:37 +0100, Thomas Gleixner wrote:
> > > > On Thu, 16 Feb 2017, Mike Galbraith wrote:
> > > >
> > > ...
> > > > > 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