Messages in this thread | | | Subject | Re: [PATCH] Fix preemptible lazy mode bug | From | Rusty Russell <> | Date | Sat, 25 Aug 2007 21:57:10 +1000 |
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On Thu, 2007-08-23 at 23:59 -0700, Zachary Amsden wrote: > Jeremy Fitzhardinge wrote: > > Hm. Doing any kind of lazy-state operation with preemption enabled is > > fundamentally meaningless. How does it get into a preemptable state > > > > Agree 100%. It is the lazy mode flush that might happen when preempt is > enabled, but lazy mode is disabled. In that case, the code relies on > per-cpu variables, which is a bad thing to do in preemtible code. This > can happen in the current code path.
Frankly, we should hoist the per-cpu state into generic paravirt code, get rid of the FLUSH "state" and only call the lazy_mode hooks when actually entering or exiting a lazy mode.
The only reason lguest doesn't use a per-cpu var is that guests are currently UP only. If that were fixed, we'd have identical VMI, Xen and lguest lazy state handing.
Cheers, Rusty.
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