From 6bfc09e2327dfbffc312004c16188dbf8dfb0297 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Fri, 19 Oct 2012 12:49:17 -0700 Subject: rcu: Provide RCU CPU stall warnings for tiny RCU Tiny RCU has historically omitted RCU CPU stall warnings in order to reduce memory requirements, however, lack of these warnings caused Thomas Gleixner some debugging pain recently. Therefore, this commit adds RCU CPU stall warnings to tiny RCU if RCU_TRACE=y. This keeps the memory footprint small, while still enabling CPU stall warnings in kernels built to enable them. Updated to include Josh Triplett's suggested use of RCU_STALL_COMMON config variable to simplify #if expressions. Reported-by: Thomas Gleixner Signed-off-by: Paul E. McKenney Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett --- init/Kconfig | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'init') diff --git a/init/Kconfig b/init/Kconfig index 7d30240e5bfe..a5e90e139ba5 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -486,6 +486,14 @@ config PREEMPT_RCU This option enables preemptible-RCU code that is common between the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations. +config RCU_STALL_COMMON + def_bool ( TREE_RCU || TREE_PREEMPT_RCU || RCU_TRACE ) + help + This option enables RCU CPU stall code that is common between + the TINY and TREE variants of RCU. The purpose is to allow + the tiny variants to disable RCU CPU stall warnings, while + making these warnings mandatory for the tree variants. + config CONTEXT_TRACKING bool -- cgit v1.2.3 From 9fc52d832b5e7f6e175f3b20ae94504b780b9fd3 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 8 Jan 2013 15:48:33 -0800 Subject: rcu: Allow TREE_PREEMPT_RCU on UP systems The TINY_PREEMPT_RCU is complex, does not provide that much memory savings, and therefore TREE_PREEMPT_RCU should be used instead. The systems where the difference between TINY_PREEMPT_RCU and TREE_PREEMPT_RCU are quite small compared to the memory footprint of CONFIG_PREEMPT. This commit therefore takes a first step towards eliminating TINY_PREEMPT_RCU by allowing TREE_PREEMPT_RCU to be configured on !SMP systems. Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett --- init/Kconfig | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'init') diff --git a/init/Kconfig b/init/Kconfig index a5e90e139ba5..fb19b46c0042 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -453,7 +453,7 @@ config TREE_RCU config TREE_PREEMPT_RCU bool "Preemptible tree-based hierarchical RCU" - depends on PREEMPT && SMP + depends on PREEMPT help This option selects the RCU implementation that is designed for very large SMP systems with hundreds or @@ -461,6 +461,8 @@ config TREE_PREEMPT_RCU is also required. It also scales down nicely to smaller systems. + Select this option if you are unsure. + config TINY_RCU bool "UP-only small-memory-footprint RCU" depends on !PREEMPT && !SMP -- cgit v1.2.3