linux-kernel - [PATCH RFC V4 00/10] jump-label: allow early jump_label

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Date:	Wed, 12 Oct 2011 17:08:31 -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>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
Subject: [PATCH RFC V4 00/10] jump-label: allow early jump_label_enable()

From: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>

[ Change from V3: Move jump_label_init() much earlier, so that the
  jump_label mechanism will be reliabily initialized before use. ]

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(), allowing it to either
insert an optimal nop, or leave the jump in place.

Part of this series makes sure that stop_machine() is safe to call
in an early pre-SMP environment, by making it just call the function
with interrupts disabled.

git://github.com/jsgf/linux-xen upstream/jump-label-noearly

Jeremy Fitzhardinge (10):
  jump_label: use proper atomic_t initializer
  stop_machine: make stop_machine safe and efficient to call early
  jump_label: if a key has already been initialized, don't nop it out
  x86/jump_label: drop arch_jump_label_text_poke_early()
  sparc/jump_label: drop arch_jump_label_text_poke_early()
  jump_label: add arch_jump_label_transform_static() to optimise
    non-live code updates
  s390/jump-label: add arch_jump_label_transform_static()
  x86/jump_label: add arch_jump_label_transform_static()
  x86/jump_label: use GENERIC_NOP5_ATOMIC instead of jmp5 +0
  jump-label: initialize jump-label subsystem much earlier

 arch/s390/kernel/jump_label.c     |   51 ++++++++++++++++++++++--------------
 arch/sparc/kernel/jump_label.c    |    8 ------
 arch/x86/include/asm/jump_label.h |    3 +-
 arch/x86/kernel/jump_label.c      |   20 ++++++++++----
 include/linux/jump_label.h        |   23 ++++++++++------
 init/main.c                       |    1 +
 kernel/jump_label.c               |   37 +++++++++++++++-----------
 kernel/stop_machine.c             |   22 ++++++++++++++++
 8 files changed, 105 insertions(+), 60 deletions(-)

-- 
1.7.6.4

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