From: Heiko Carstens , "Paul E. McKenney" 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 Signed-off-by: Andrew Morton --- include/linux/rcupdate.h | 1 + kernel/rcupdate.c | 8 ++++++++ 2 files changed, 9 insertions(+) diff -puN include/linux/rcupdate.h~rcu-introduce-rcu_needs_cpu-interface include/linux/rcupdate.h --- 25/include/linux/rcupdate.h~rcu-introduce-rcu_needs_cpu-interface Wed Apr 26 14:12:13 2006 +++ 25-akpm/include/linux/rcupdate.h Wed Apr 26 14:12:13 2006 @@ -132,6 +132,7 @@ static inline void rcu_bh_qsctr_inc(int } 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 -puN kernel/rcupdate.c~rcu-introduce-rcu_needs_cpu-interface kernel/rcupdate.c --- 25/kernel/rcupdate.c~rcu-introduce-rcu_needs_cpu-interface Wed Apr 26 14:12:13 2006 +++ 25-akpm/kernel/rcupdate.c Wed Apr 26 14:12:13 2006 @@ -485,6 +485,14 @@ int rcu_pending(int cpu) __rcu_pending(&rcu_bh_ctrlblk, &per_cpu(rcu_bh_data, cpu)); } +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 || _