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

On Thu, 17 Jan 2013, Steven Rostedt wrote:

In slab_alloc_node(), after the cpu_slab is assigned, if the task is
preempted and moves to another CPU, there's nothing keeping the page and
object in sync. The -rt kernel crashed because page was NULL and object
was not, and the node_match() dereferences page. Even though the crash
happened on -rt, there's nothing that's keeping this from happening on
mainline.

The easiest fix is to disable interrupts for the entire time from
acquiring the current CPU cpu_slab and assigning the object and page.
After that, it's fine to allow preemption.

Its easiest to just check for the NULL pointer as initally done. The call
to __slab_alloc can do what the fastpath does.

And the fastpath will verify that the c->page pointer was not changed.

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>