Commit 32aa2f41 authored by Frederic Weisbecker's avatar Frederic Weisbecker Committed by Paul E. McKenney
Browse files

rcu/nocb: Process batch locally as long as offloading isn't complete 



This commit makes sure to process the callbacks locally (via either
RCU_SOFTIRQ or the rcuc kthread) whenever the segcblist isn't entirely
offloaded.  This ensures that callbacks are invoked one way or another
while a CPU is in the middle of a toggle operation.

Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Neeraj Upadhyay <neeraju@codeaurora.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Inspired-by: default avatarPaul E. McKenney <paulmck@kernel.org>
Tested-by: default avatarBoqun Feng <boqun.feng@gmail.com>
Signed-off-by: default avatarFrederic Weisbecker <frederic@kernel.org>
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent e3abe959

kernel/rcu/rcu_segcblist.h

+12 −0
Original line number Diff line number Diff line
@@ -95,6 +95,18 @@ static inline bool rcu_segcblist_is_offloaded(struct rcu_segcblist *rsclp) 
	return false;

}



static inline bool rcu_segcblist_completely_offloaded(struct rcu_segcblist *rsclp)

{

	int flags = SEGCBLIST_KTHREAD_CB | SEGCBLIST_KTHREAD_GP | SEGCBLIST_OFFLOADED;



	if (IS_ENABLED(CONFIG_RCU_NOCB_CPU)) {

		if ((rsclp->flags & flags) == flags)

			return true;

	}



	return false;

}



/*

 * Are all segments following the specified segment of the specified

 * rcu_segcblist structure empty of callbacks?  (The specified

kernel/rcu/tree.c

+2 −1
Original line number Diff line number Diff line
@@ -2700,6 +2700,7 @@ static __latent_entropy void rcu_core(void) 
	struct rcu_data *rdp = raw_cpu_ptr(&rcu_data);

	struct rcu_node *rnp = rdp->mynode;

	const bool offloaded = rcu_segcblist_is_offloaded(&rdp->cblist);

	const bool do_batch = !rcu_segcblist_completely_offloaded(&rdp->cblist);



	if (cpu_is_offline(smp_processor_id()))

		return;
@@ -2729,7 +2730,7 @@ static __latent_entropy void rcu_core(void) 
	rcu_check_gp_start_stall(rnp, rdp, rcu_jiffies_till_stall_check());



	/* If there are callbacks ready, invoke them. */

	if (!offloaded && rcu_segcblist_ready_cbs(&rdp->cblist) &&

	if (do_batch && rcu_segcblist_ready_cbs(&rdp->cblist) &&

	    likely(READ_ONCE(rcu_scheduler_fully_active)))

		rcu_do_batch(rdp);