[PATCH tip/core/rcu 0/4] Programmatic nestable expedited grace periods

From: Paul E. McKenney
Date: Fri Feb 20 2015 - 00:09:03 EST


This series, possibly for v3.21, contains changes that allow in-kernel
code to specify that all subsequent synchronous grace-period primitives
(synchronize_rcu() and friends) be expedited. New rcu_expedite_gp()
and rcu_unexpedite_gp() primitives enable and disable expediting,
and these may be nested. Note that the rcu_expedited boot/sysfs
variable, if non-zero, causes expediting to happen regardless of calls
to rcu_expedite_gp().

Because one of the use cases for these primitives is to expedite
grace periods during the in-kernel portion of boot, a new Kconfig
parameter named CONFIG_RCU_EXPEDITE_BOOT causes the kernel to act
as if rcu_expedite_gp() was called very early in boot. At the end
of boot (presumably just before init is spawned), a call to
rcu_end_inkernel_boot() will provide the matching rcu_unexpedite_gp()
if required.

The patches in this series are as follows:

1. Add rcu_expedite_gp() and rcu_unexpedite_gp() functions.

2. Add rcutorture tests for rcu_expedite_gp() and rcu_unexpedite_gp().

3. Change open-coded access to the rcu_expedited variable to
instead use a new rcu_gp_is_expedited() function.

4. Add the CONFIG_RCU_EXPEDITE_BOOT Kconfig parameter and
the rcu_end_inkernel_boot() function.

This passes light rcutorture testing.

Thanx, Paul


b/include/linux/rcupdate.h | 21 ++++++++++++++++
b/init/Kconfig | 13 +++++++++
b/kernel/rcu/rcutorture.c | 24 ++++++++++++++++++
b/kernel/rcu/srcu.c | 2 -
b/kernel/rcu/tree.c | 9 +++---
b/kernel/rcu/tree_plugin.h | 2 -
b/kernel/rcu/update.c | 59 ++++++++++++++++++++++++++++++++++++++++++++-
7 files changed, 123 insertions(+), 7 deletions(-)

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