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

[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

include/linux/rcupdate.h

+1 −0
Original line number Diff line number Diff line
@@ -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.

kernel/rcupdate.c

+19 −0
Original line number Diff line number Diff line
@@ -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 ||

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