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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2009-08-22 16:56:52 -0400
committerIngo Molnar <mingo@elte.hu>2009-08-23 04:32:40 -0400
commitf41d911f8c49a5d65c86504c19e8204bb605c4fd (patch)
tree59bcd3048652ef290b3e19d2904409afd5c90eb3 /lib/Kconfig.debug
parenta157229cabd6dd8cfa82525fc9bf730c94cc9ac2 (diff)
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>
Diffstat (limited to 'lib/Kconfig.debug')
-rw-r--r--lib/Kconfig.debug2
1 files changed, 1 insertions, 1 deletions
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
725 725
726config RCU_CPU_STALL_DETECTOR 726config RCU_CPU_STALL_DETECTOR
727 bool "Check for stalled CPUs delaying RCU grace periods" 727 bool "Check for stalled CPUs delaying RCU grace periods"
728 depends on CLASSIC_RCU || TREE_RCU 728 depends on CLASSIC_RCU || TREE_RCU || TREE_PREEMPT_RCU
729 default n 729 default n
730 help 730 help
731 This option causes RCU to printk information on which 731 This option causes RCU to printk information on which