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authorHeiko Carstens <heiko.carstens@de.ibm.com>2006-05-15 12:43:58 -0400
committerLinus Torvalds <torvalds@g5.osdl.org>2006-05-15 14:20:55 -0400
commit986733e01d258c26107f1da9d8d47c718349ad2f (patch)
tree5e0f04a707b8c341f79927ba6fffd0ad55d85c29
parent3b7c8108273bed41a2fc04533cc9f2026ff38c8e (diff)
[PATCH] RCU: introduce rcu_needs_cpu() interface
With "Paul E. McKenney" <paulmck@us.ibm.com> Introduce rcu_needs_cpu() interface. This can be used to tell if there will be a new rcu batch on a cpu soon by looking at the curlist pointer. This can be used to avoid to enter a tickless idle state where the cpu would miss that a new batch is ready when rcu_start_batch would be called on a different cpu. Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: "Paul E. McKenney" <paulmck@us.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--include/linux/rcupdate.h1
-rw-r--r--kernel/rcupdate.c19
2 files changed, 20 insertions, 0 deletions
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 5673008b61e1..970284f571a6 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -132,6 +132,7 @@ static inline void rcu_bh_qsctr_inc(int cpu)
132} 132}
133 133
134extern int rcu_pending(int cpu); 134extern int rcu_pending(int cpu);
135extern int rcu_needs_cpu(int cpu);
135 136
136/** 137/**
137 * rcu_read_lock - mark the beginning of an RCU read-side critical section. 138 * rcu_read_lock - mark the beginning of an RCU read-side critical section.
diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index 6d32ff26f948..2058f88c7bbb 100644
--- a/kernel/rcupdate.c
+++ b/kernel/rcupdate.c
@@ -479,12 +479,31 @@ static int __rcu_pending(struct rcu_ctrlblk *rcp, struct rcu_data *rdp)
479 return 0; 479 return 0;
480} 480}
481 481
482/*
483 * Check to see if there is any immediate RCU-related work to be done
484 * by the current CPU, returning 1 if so. This function is part of the
485 * RCU implementation; it is -not- an exported member of the RCU API.
486 */
482int rcu_pending(int cpu) 487int rcu_pending(int cpu)
483{ 488{
484 return __rcu_pending(&rcu_ctrlblk, &per_cpu(rcu_data, cpu)) || 489 return __rcu_pending(&rcu_ctrlblk, &per_cpu(rcu_data, cpu)) ||
485 __rcu_pending(&rcu_bh_ctrlblk, &per_cpu(rcu_bh_data, cpu)); 490 __rcu_pending(&rcu_bh_ctrlblk, &per_cpu(rcu_bh_data, cpu));
486} 491}
487 492
493/*
494 * Check to see if any future RCU-related work will need to be done
495 * by the current CPU, even if none need be done immediately, returning
496 * 1 if so. This function is part of the RCU implementation; it is -not-
497 * an exported member of the RCU API.
498 */
499int rcu_needs_cpu(int cpu)
500{
501 struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
502 struct rcu_data *rdp_bh = &per_cpu(rcu_bh_data, cpu);
503
504 return (!!rdp->curlist || !!rdp_bh->curlist || rcu_pending(cpu));
505}
506
488void rcu_check_callbacks(int cpu, int user) 507void rcu_check_callbacks(int cpu, int user)
489{ 508{
490 if (user || 509 if (user ||