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[PATCH] RCU: introduce rcu_needs_cpu() interface

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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>
This commit is contained in:
Heiko Carstens 2006-05-15 09:43:58 -07:00 committed by Linus Torvalds
parent 3b7c810827
commit 986733e01d
2 changed files with 20 additions and 0 deletions
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1
include/linux/rcupdate.h
View file

@ -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.

19
kernel/rcupdate.c
View file

@ -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 ||