Re: [RFC][PATCH v2] slub: Keep page and object in sync inslab_alloc_node()

From: Joonsoo Kim
Date: Mon Jan 21 2013 - 03:11:13 EST


On Fri, Jan 18, 2013 at 10:55:01AM -0500, Steven Rostedt wrote:
> On Fri, 2013-01-18 at 10:04 -0500, Steven Rostedt wrote:
>
> Just to be more complete:
>
> > CPU0 CPU1
> > ---- ----
> c = __this_cpu_ptr(s->cpu_slab);
> <migrates to CPU0>
>
> > <cpu fetches c->page>
> <another task>
>
> > updates c->tid
> > updates c->page
> > updates c->freelist
> > <cpu fetches c->tid>
> > <cpu fetches c->freelist>
> >
> > node_match() succeeds even though
> > current c->page wont
> >
>
> <migrates back to CPU 1>

Hello.
I have one stupid question just for curiosity.
Does the processor re-order instructions which load data from same cacheline?

> > this_cpu_cmpxchg_double() only tests
> > the object (freelist) and tid, both which
> > will match, but the page that was tested
> > isn't the right one.
> >
>
> Yes, it's very unlikely, but we are in the business of dealing with the
> very unlikely. That's because in our business, the very unlikely is very
> likely. Damn, I need to buy a lotto ticket!
>
> -- Steve
>
>
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majordomo@xxxxxxxxxx For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/