From: Andi Kleen <ak@muc.de>
To: torvalds@transmeta.com (Linus Torvalds)
Cc: jakub@redhat.com, linux-kernel@vger.kernel.org
Subject: Re: Why is get_current() not const function?
Date: Mon, 17 Mar 2003 18:26:05 +0100 [thread overview]
Message-ID: <m3u1e1ykeq.fsf@averell.firstfloor.org> (raw)
In-Reply-To: <b53pqi$ud9$1@penguin.transmeta.com.suse.lists.linux.kernel> (torvalds@transmeta.com's message of "17 Mar 2003 07:29:40 +0100")
torvalds@transmeta.com (Linus Torvalds) writes:
>> and why on x86-64
>>the movq %%gs:0, %0 inline asm is volatile with "memory" clobber?
>
> Can't help you on that one, but it looks like it uses various helper
> functions for doing the x86-64 per-processor data structures, and I bet
> those helper functions are shared by _other_ users who definitely want
> to have their data properly re-read. Ie "current()" may be constant in
> process context, but that sure isn't true about a lot of other things in
> the per-processor data structures.
Yes, that's the big issue. const current requires non volatile read_pda()
and making read_pda non volatile breaks lots of code currently and probably
needs an audit over all users.
-Andi
next prev parent reply other threads:[~2003-03-17 17:15 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20030313061926.S3910@devserv.devel.redhat.com.suse.lists.linux.kernel>
2003-03-13 13:31 ` Why is get_current() not const function? Andi Kleen
[not found] ` <b53pqi$ud9$1@penguin.transmeta.com.suse.lists.linux.kernel>
2003-03-17 17:26 ` Andi Kleen [this message]
2003-03-17 17:39 ` Jakub Jelinek
2003-03-17 19:11 Manfred Spraul
-- strict thread matches above, loose matches on Subject: below --
2003-03-13 11:19 Jakub Jelinek
2003-03-17 6:26 ` Linus Torvalds
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