From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: David Miller <davem@davemloft.net>
Cc: hugh@veritas.com, linux-mm@kvack.org,
torvalds@linux-foundation.org, akpm@linux-foundation.org,
npiggin@suse.de, zach@vmware.com, jeremy@goop.org
Subject: Re: tlb_gather_mmu() and semantics of "fullmm"
Date: Fri, 27 Mar 2009 17:10:35 +1100 [thread overview]
Message-ID: <1238134235.20197.64.camel@pasglop> (raw)
In-Reply-To: <20090326.225744.250374539.davem@davemloft.net>
On Thu, 2009-03-26 at 22:57 -0700, David Miller wrote:
> Good point.
>
> Maybe it would work out correctly if I used current->mm?
>
> Because if I tested it that way, only something really executing
> in userland could force the cpumask bit clears.
>
> Any kernel thread would flush the TLB if and when it switched
> back into a real task using that mm.
>
> Sound good?
/me thinks (not as late here but I'm getting tired regardless ;-)
So if you test current->mm, you effectively account for mm_users == 1,
so the only way the mm can be active on another processor is as a lazy
mm for a kernel thread. So your test should work properly as long
as you don't have a HW that will do speculative TLB reloads into the
TLB on that other CPU (and even if you do, you flush-on-switch-in should
get rid of any crap here).
Ben.
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next prev parent reply other threads:[~2009-03-27 6:03 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-26 5:01 Benjamin Herrenschmidt
2009-03-26 14:08 ` Hugh Dickins
2009-03-26 16:38 ` Linus Torvalds
2009-03-26 23:13 ` Benjamin Herrenschmidt
2009-03-26 17:21 ` Jeremy Fitzhardinge
2009-03-26 20:39 ` David Miller
2009-03-26 22:33 ` Benjamin Herrenschmidt
2009-03-27 5:04 ` David Miller
2009-03-27 5:38 ` Benjamin Herrenschmidt
2009-03-27 5:44 ` David Miller
2009-03-27 5:54 ` Benjamin Herrenschmidt
2009-03-27 5:57 ` David Miller
2009-03-27 6:10 ` Benjamin Herrenschmidt [this message]
2009-03-27 8:05 ` David Miller
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