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| author | Heiko Carstens <heiko.carstens@de.ibm.com> | 2006-05-15 09:43:58 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-05-15 11:20:55 -0700 |
| commit | 986733e01d258c26107f1da9d8d47c718349ad2f (patch) | |
| tree | 5e0f04a707b8c341f79927ba6fffd0ad55d85c29 | |
| parent | 3b7c8108273bed41a2fc04533cc9f2026ff38c8e (diff) | |
| download | lwn-986733e01d258c26107f1da9d8d47c718349ad2f.tar.gz lwn-986733e01d258c26107f1da9d8d47c718349ad2f.zip | |
[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.h | 1 | ||||
| -rw-r--r-- | kernel/rcupdate.c | 19 |
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) } extern int rcu_pending(int cpu); +extern int rcu_needs_cpu(int cpu); /** * 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) return 0; } +/* + * Check to see if there is any immediate RCU-related work to be done + * by the current CPU, returning 1 if so. This function is part of the + * RCU implementation; it is -not- an exported member of the RCU API. + */ int rcu_pending(int cpu) { return __rcu_pending(&rcu_ctrlblk, &per_cpu(rcu_data, cpu)) || __rcu_pending(&rcu_bh_ctrlblk, &per_cpu(rcu_bh_data, cpu)); } +/* + * Check to see if any future RCU-related work will need to be done + * by the current CPU, even if none need be done immediately, returning + * 1 if so. This function is part of the RCU implementation; it is -not- + * an exported member of the RCU API. + */ +int rcu_needs_cpu(int cpu) +{ + struct rcu_data *rdp = &per_cpu(rcu_data, cpu); + struct rcu_data *rdp_bh = &per_cpu(rcu_bh_data, cpu); + + return (!!rdp->curlist || !!rdp_bh->curlist || rcu_pending(cpu)); +} + void rcu_check_callbacks(int cpu, int user) { if (user || |