Messages in this thread | | | From | Linus Torvalds <> | Date | Wed, 2 Feb 2011 17:55:52 -0800 | Subject | Re: [patch] x86, mm: avoid stale tlb entries by clearing prev mm_cpumask after switching mm |
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On Wed, Feb 2, 2011 at 12:07 PM, Suresh Siddha <suresh.b.siddha@intel.com> wrote: > For the prev mm that is handing over the cpu to another mm, clear the cpu > from the mm_cpumask(prev) after the cr3 is changed. > > Otherwise, clearing the mm_cpumask early will avoid the flush tlb IPI's while > the cr3 and TLB's are still pointing to the prev mm. And this window can lead > to the stale (global) TLB entries.
Why?
This looks pointless. Explain why this matters. Global entries are never per-mm, so any global entries can never care about the mm_cpumask.
And for any normal entries it doesn't matter if the IPI gets lost, since the TLB will be flushed (immediately afterwards) by the cr3 write.
So no, I will not accept this patch, and it shouldn't be marked for stable. Unless you can show exactly what is the point of it, and exactly what the bug is.
Linus
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