[PATCH RFC V3 0/8] jump-label: allow early jump_label_enable()

[Jeremy Fitzhardinge <jeremy@goop.org>]

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

[ Change from V2: add arch_jump_label_transform_static() for use on
  code which can't possibly be currently executing (ie, a freshly
  loaded module), which can avoid heavyweight things like
  stop_machine.  The default implementation is simply
  arch_jump_label_transform(), so only architectures which would
  particularly benefit need implement it (x86 and s390 in this
  series). ]

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 (8):
  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()

 arch/s390/kernel/jump_label.c  |   51 ++++++++++++++++++++++++---------------
 arch/sparc/kernel/jump_label.c |    8 ------
 arch/x86/kernel/jump_label.c   |   20 +++++++++++----
 include/linux/jump_label.h     |    9 ++++---
 kernel/jump_label.c            |   32 +++++++++++++++---------
 kernel/stop_machine.c          |   22 +++++++++++++++++
 6 files changed, 92 insertions(+), 50 deletions(-)

-- 
1.7.6.4