Messages in this thread | | | Date | Fri, 20 Feb 2009 18:14:27 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH] mm: fix lazy vmap purging (use-after-free error) |
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* Paul E. McKenney <paulmck@linux.vnet.ibm.com> wrote:
> > > So, what flavor of RCU were you using? > > > > well, even in preemptible RCU the grace period should be > > extended as long as we are non-preempt (which we are here), > > correct? > > Given Classic RCU, you are quite correct. With preemptable > RCU, if there are no readers, and if irqs are enabled, the > grace period could end within the spinlock's critical section. > Of course, the spinlock would need to be held for an > improbably long time -- many milliseconds.
ah. But we _can_ get unlucky there and get into multiple-milliseconds of blockage: for example if some heavy interrupt source or softirq processes stuff for many milliseconds.
So it's a real fix needed both for mainline and for 2.6.28. And kudos to kmemcheck ;-)
Ingo
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