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authorPaul E. McKenney <paul.mckenney@linaro.org>2013-01-07 13:37:42 -0800
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2013-03-12 11:17:51 -0700
commit34ed62461ae4970695974afb9a60ac3df0086830 (patch)
treed65a582953a66ee089074fd5a57e39460d4ce2c6 /init
parentf6161aa153581da4a3867a2d1a7caf4be19b6ec9 (diff)
downloadlinux-34ed62461ae4970695974afb9a60ac3df0086830.tar.gz
rcu: Remove restrictions on no-CBs CPUs
Currently, CPU 0 is constrained to not be a no-CBs CPU, and furthermore at least one no-CBs CPU must remain online at any given time. These restrictions are problematic in some situations, such as cases where all CPUs must run a real-time workload that needs to be insulated from OS jitter and latencies due to RCU callback invocation. This commit therefore provides no-CBs CPUs a (very crude and energy-inefficient) way to start and to wait for grace periods independently of the normal RCU callback mechanisms. This approach allows any or all of the CPUs to be designated as no-CBs CPUs, and allows any proper subset of the CPUs (whether no-CBs CPUs or not) to be offlined. This commit also provides a fix for a locking bug spotted by Xie ChanglongX <changlongx.xie@intel.com>. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'init')
-rw-r--r--init/Kconfig4
1 files changed, 2 insertions, 2 deletions
diff --git a/init/Kconfig b/init/Kconfig
index 22616cd434b..c8bd349eb63 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -655,7 +655,7 @@ config RCU_BOOST_DELAY
Accept the default if unsure.
config RCU_NOCB_CPU
- bool "Offload RCU callback processing from boot-selected CPUs"
+ bool "Offload RCU callback processing from boot-selected CPUs (EXPERIMENTAL"
depends on TREE_RCU || TREE_PREEMPT_RCU
default n
help
@@ -673,7 +673,7 @@ config RCU_NOCB_CPU
callback, and (2) affinity or cgroups can be used to force
the kthreads to run on whatever set of CPUs is desired.
- Say Y here if you want reduced OS jitter on selected CPUs.
+ Say Y here if you want to help to debug reduced OS jitter.
Say N here if you are unsure.
endmenu # "RCU Subsystem"