[PATCH RFC V2 0/5] jump-label: allow early jump_label_enable()

Jeremy Fitzhardinge
2011-10-01T21:55:48Z

From: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.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