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From: Ingo Molnar <mingo@elte.hu>
To: davidm@hpl.hp.com
Cc: "David S. Miller" <davem@davemloft.net>,
	tony.luck@intel.com, linux-kernel@vger.kernel.org
Subject: Re: [patch] sched: unlocked context-switches
Date: Tue, 12 Apr 2005 08:42:53 +0200	[thread overview]
Message-ID: <20050412064253.GA1289@elte.hu> (raw)
In-Reply-To: <16987.7956.806699.617633@napali.hpl.hp.com>


* David Mosberger <davidm@napali.hpl.hp.com> wrote:

> Now, Ingo says that the order is reversed with his patch, i.e., 
> switch_mm() happens after switch_to().  That means flush_tlb_mm() may 
> now see a current->active_mm which hasn't really been activated yet.  
> That should be OK since it would just mean that we'd do an early (and 
> duplicate) activate_context().  While it does not give me a warm and 
> fuzzy feeling to have this inconsistent state be observable by 
> interrupt-handlers (and, in particular, IPI-handlers), I don't see any 
> problem with it off hand.

thanks for the analysis. I fundamentally dont have any fuzzy feeling 
from having _any_ portion of the context-switch path nonatomic, but with 
more complex hardware it's just not possible it seems.

	Ingo

  parent reply	other threads:[~2005-04-12  6:43 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <3R6Ir-89Y-23@gated-at.bofh.it>
2005-04-09  6:32 ` [patch] sched: unlocked context-switches David Mosberger-Tang
2005-04-09  7:07   ` Ingo Molnar
2005-04-09  7:15     ` David Mosberger
2005-04-09 22:58       ` David S. Miller
2005-04-10  6:43         ` Ingo Molnar
2005-04-12  1:06           ` David Mosberger
2005-04-12  2:12             ` Nick Piggin
2005-04-12 17:14               ` David Mosberger
2005-04-13  3:26                 ` Nick Piggin
2005-04-12  6:42             ` Ingo Molnar [this message]
2005-04-12 17:15               ` David Mosberger
2005-04-08 18:38 Luck, Tony
2005-04-08 18:38 ` Luck, Tony
2005-04-09  4:38 ` Ingo Molnar
2005-04-09  6:28   ` Nick Piggin
2005-04-09  6:55     ` Ingo Molnar
2005-04-09  7:11       ` Nick Piggin
2005-04-09  9:22   ` Benjamin Herrenschmidt
2005-04-09 22:46     ` David S. Miller
2005-04-10  7:23       ` Richard Henderson
  -- strict thread matches above, loose matches on Subject: below --
2005-04-08 12:16 Ingo Molnar
2005-04-29  9:09 ` Andrew Morton

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