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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2009-08-22 13:56:52 -0700
committerIngo Molnar <mingo@elte.hu>2009-08-23 10:32:40 +0200
commitf41d911f8c49a5d65c86504c19e8204bb605c4fd (patch)
tree59bcd3048652ef290b3e19d2904409afd5c90eb3 /include/linux/init_task.h
parenta157229cabd6dd8cfa82525fc9bf730c94cc9ac2 (diff)
downloadlinux-linaro-stable-f41d911f8c49a5d65c86504c19e8204bb605c4fd.tar.gz
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 'include/linux/init_task.h')
-rw-r--r--include/linux/init_task.h15
1 files changed, 15 insertions, 0 deletions
diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index 7fc01b13be43..971a968831bf 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -94,6 +94,20 @@ extern struct group_info init_groups;
# define CAP_INIT_BSET CAP_INIT_EFF_SET
#endif
+#ifdef CONFIG_PREEMPT_RCU
+#define INIT_TASK_RCU_PREEMPT(tsk) \
+ .rcu_read_lock_nesting = 0, \
+ .rcu_flipctr_idx = 0,
+#elif defined(CONFIG_TREE_PREEMPT_RCU)
+#define INIT_TASK_RCU_PREEMPT(tsk) \
+ .rcu_read_lock_nesting = 0, \
+ .rcu_read_unlock_special = 0, \
+ .rcu_blocked_cpu = -1, \
+ .rcu_node_entry = LIST_HEAD_INIT(tsk.rcu_node_entry),
+#else
+#define INIT_TASK_RCU_PREEMPT(tsk)
+#endif
+
extern struct cred init_cred;
#ifdef CONFIG_PERF_COUNTERS
@@ -173,6 +187,7 @@ extern struct cred init_cred;
INIT_LOCKDEP \
INIT_FTRACE_GRAPH \
INIT_TRACE_RECURSION \
+ INIT_TASK_RCU_PREEMPT(tsk) \
}