linux-kernel - [PATCH RFC V2 0/5] jump-label: allow early jump_label

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Date:	Sat,  1 Oct 2011 14:55:32 -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 V2 0/5] jump-label: allow early jump_label_enable()

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

[ This is a new version of this series, which drops the need for any
  special _early() function in favour of making sure stop_machine()
  can operate correctly and efficiently in a pre-SMP envronment. ]

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 (5):
  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()

 arch/sparc/kernel/jump_label.c |    8 --------
 arch/x86/kernel/jump_label.c   |    6 ------
 include/linux/jump_label.h     |    7 ++++---
 kernel/jump_label.c            |   20 ++++++++------------
 kernel/stop_machine.c          |   21 +++++++++++++++++++++
 5 files changed, 33 insertions(+), 29 deletions(-)

-- 
1.7.6.2

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