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To: linux-kernel@vger.kernel.org
From: torvalds@transmeta.com (Linus Torvalds)
Subject: Re: Why is get_current() not const function?
Date: Mon, 17 Mar 2003 06:26:26 +0000 (UTC)
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References: <20030313061926.S3910@devserv.devel.redhat.com>
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In article <20030313061926.S3910@devserv.devel.redhat.com>,
Jakub Jelinek  <jakub@redhat.com> wrote:
>
>Anyone remembers why get_current function (on arches which define
>current to get_current()) is not const

Because it makes no difference at all on x86, since gcc will ignore
"const" for inline functions. At least that used to be true.

>					 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.

		Linus
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