Commit 986733e0 authored by Heiko Carstens's avatar Heiko Carstens Committed by Linus Torvalds

[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: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 3b7c8108
...@@ -132,6 +132,7 @@ static inline void rcu_bh_qsctr_inc(int cpu) ...@@ -132,6 +132,7 @@ static inline void rcu_bh_qsctr_inc(int cpu)
} }
extern int rcu_pending(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. * rcu_read_lock - mark the beginning of an RCU read-side critical section.
......
...@@ -479,12 +479,31 @@ static int __rcu_pending(struct rcu_ctrlblk *rcp, struct rcu_data *rdp) ...@@ -479,12 +479,31 @@ static int __rcu_pending(struct rcu_ctrlblk *rcp, struct rcu_data *rdp)
return 0; 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) int rcu_pending(int cpu)
{ {
return __rcu_pending(&rcu_ctrlblk, &per_cpu(rcu_data, cpu)) || return __rcu_pending(&rcu_ctrlblk, &per_cpu(rcu_data, cpu)) ||
__rcu_pending(&rcu_bh_ctrlblk, &per_cpu(rcu_bh_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) void rcu_check_callbacks(int cpu, int user)
{ {
if (user || if (user ||
......
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