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

From: Jeremy Fitzhardinge
Date: Tue Oct 04 2011 - 15:18:30 EST

From: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>

[ 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

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(-)


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