lkml.org 
[lkml]   [2011]   [Feb]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [patch] x86, mm: avoid stale tlb entries by clearing prev mm_cpumask after switching mm
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


\
 
 \ /
  Last update: 2011-02-03 02:59    [W:0.050 / U:11.720 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site