From f41d911f8c49a5d65c86504c19e8204bb605c4fd Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Date: Sat, 22 Aug 2009 13:56:52 -0700 Subject: rcu: Merge preemptable-RCU functionality into hierarchical RCU Create a kernel/rcutree_plugin.h file that contains definitions for preemptable RCU (or, under the #else branch of the #ifdef, empty definitions for the classic non-preemptable semantics). These definitions fit into plugins defined in kernel/rcutree.c for this purpose. This variant of preemptable RCU uses a new algorithm whose read-side expense is roughly that of classic hierarchical RCU under CONFIG_PREEMPT. This new algorithm's update-side expense is similar to that of classic hierarchical RCU, and, in absence of read-side preemption or blocking, is exactly that of classic hierarchical RCU. Perhaps more important, this new algorithm has a much simpler implementation, saving well over 1,000 lines of code compared to mainline's implementation of preemptable RCU, which will hopefully be retired in favor of this new algorithm. The simplifications are obtained by maintaining per-task nesting state for running tasks, and using a simple lock-protected algorithm to handle accounting when tasks block within RCU read-side critical sections, making use of lessons learned while creating numerous user-level RCU implementations over the past 18 months. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: akpm@linux-foundation.org Cc: mathieu.desnoyers@polymtl.ca Cc: josht@linux.vnet.ibm.com Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org LKML-Reference: <12509746134003-git-send-email-> Signed-off-by: Ingo Molnar <mingo@elte.hu> --- lib/Kconfig.debug | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'lib') diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 12327b2bb785..f87fb0c8f924 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -725,7 +725,7 @@ config RCU_TORTURE_TEST_RUNNABLE config RCU_CPU_STALL_DETECTOR bool "Check for stalled CPUs delaying RCU grace periods" - depends on CLASSIC_RCU || TREE_RCU + depends on CLASSIC_RCU || TREE_RCU || TREE_PREEMPT_RCU default n help This option causes RCU to printk information on which -- cgit v1.2.2 From 6b3ef48adf847f7adf11c870e3ffacac150f1564 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Date: Sat, 22 Aug 2009 13:56:53 -0700 Subject: rcu: Remove CONFIG_PREEMPT_RCU Now that CONFIG_TREE_PREEMPT_RCU is in place, there is no further need for CONFIG_PREEMPT_RCU. Remove it, along with whatever subtle bugs it may (or may not) contain. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: akpm@linux-foundation.org Cc: mathieu.desnoyers@polymtl.ca Cc: josht@linux.vnet.ibm.com Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org LKML-Reference: <125097461396-git-send-email-> Signed-off-by: Ingo Molnar <mingo@elte.hu> --- lib/Kconfig.debug | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'lib') diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index f87fb0c8f924..82fbc49728df 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -725,7 +725,7 @@ config RCU_TORTURE_TEST_RUNNABLE config RCU_CPU_STALL_DETECTOR bool "Check for stalled CPUs delaying RCU grace periods" - depends on CLASSIC_RCU || TREE_RCU || TREE_PREEMPT_RCU + depends on TREE_RCU || TREE_PREEMPT_RCU default n help This option causes RCU to printk information on which -- cgit v1.2.2