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Message-Id: <cover.1317338254.git.jeremy.fitzhardinge@citrix.com>
Date: Thu, 29 Sep 2011 16:26:30 -0700
From: Jeremy Fitzhardinge <jeremy@...p.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: "David S. Miller" <davem@...emloft.net>,
David Daney <david.daney@...ium.com>,
Michael Ellerman <michael@...erman.id.au>,
Jan Glauber <jang@...ux.vnet.ibm.com>,
Jason Baron <jbaron@...hat.com>,
the arch/x86 maintainers <x86@...nel.org>,
Xen Devel <xen-devel@...ts.xensource.com>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
Subject: [PATCH RFC 0/8] jump-label: allow early jump_label_enable()
From: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
Hi all,
While trying to use the jump-label stuff for my PV ticketlock changes,
I had some problems using jump labels early in the kernel's lifetime
(pre-SMP).
The basic problem is that even if I enable a jump_label_key, the
jump_label_init() initializer ends up nopping out all the code sites.
This series enables early use of jump labels by making
jump_label_init() respect already-enabled keys.
To do this, I've dropped arch_jump_label_poke_text_early() and
replaced it with arch_jump_label_transform_early(), which is the same
as the non-_early variant except that it expects to be operating in a
pre-SMP environment.
I've tested this on x86, but all the other architecture changes are
completely untested (not even breathed on by a compiler).
One big question which arises is whether the _early() function is
necessary at all. All the stop_machine/mutex/etc stuff that
arch_jump_label_transform() ends up doing is redundant pre-SMP, but it
shouldn't hurt. Maybe we can just drop the _early function? It works
on x86, at least, because jump_label_enable() works, which uses the full
form. And dropping it would reduce this to a very much smaller series.
Thanks,
J
Jeremy Fitzhardinge (8):
jump_label: use proper atomic_t initializer
jump_label: if a key has already been initialized, don't nop it out
x86/jump_label: add arch_jump_label_transform_early()
sparc/jump_label: add arch_jump_label_transform_early()
mips/jump_label: add arch_jump_label_transform_early()
powerpc/jump_label: add arch_jump_label_transform_early()
s390/jump-label: add arch_jump_label_transform_early()
jump_label: drop default arch_jump_label_transform_early
arch/mips/kernel/jump_label.c | 21 +++++++++++++---
arch/powerpc/kernel/jump_label.c | 6 ++++
arch/s390/kernel/jump_label.c | 49 +++++++++++++++++++++++--------------
arch/sparc/kernel/jump_label.c | 24 +++++++++++-------
arch/x86/kernel/jump_label.c | 20 +++++++++++----
include/linux/jump_label.h | 7 +++--
kernel/jump_label.c | 20 ++++++---------
7 files changed, 94 insertions(+), 53 deletions(-)
--
1.7.6.2
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