Messages in this thread | | | Subject | Re: [RFC][PATCH v2] slub: Keep page and object in sync in slab_alloc_node() | From | Steven Rostedt <> | Date | Fri, 18 Jan 2013 10:55:01 -0500 |
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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>
> 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
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