Commit 57881863 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu-tasks: Abstract invocations of callbacks 



This commit adds a rcu_tasks_invoke_cbs() function that invokes all
ready callbacks on all of the per-CPU lists that are currently in use.

Reported-by: default avatarMartin Lau <kafai@fb.com>
Cc: Neeraj Upadhyay <neeraj.iitr10@gmail.com>
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent 4d1114c0

kernel/rcu/tasks.h

+34 −22
Original line number Diff line number Diff line
@@ -255,14 +255,42 @@ static int rcu_tasks_need_gpcb(struct rcu_tasks *rtp) 
	return needgpcb;

}



/* RCU-tasks kthread that detects grace periods and invokes callbacks. */

static int __noreturn rcu_tasks_kthread(void *arg)

// Advance callbacks and invoke any that are ready.

static void rcu_tasks_invoke_cbs(struct rcu_tasks *rtp)

{

	int cpu;

	unsigned long flags;

	int len;

	int needgpcb;

	struct rcu_cblist rcl = RCU_CBLIST_INITIALIZER(rcl);

	struct rcu_head *rhp;



	for (cpu = 0; cpu < rtp->percpu_enqueue_lim; cpu++) {

		struct rcu_tasks_percpu *rtpcp = per_cpu_ptr(rtp->rtpcpu, cpu);



		if (rcu_segcblist_empty(&rtpcp->cblist))

			continue;

		raw_spin_lock_irqsave_rcu_node(rtpcp, flags);

		rcu_segcblist_advance(&rtpcp->cblist, rcu_seq_current(&rtp->tasks_gp_seq));

		rcu_segcblist_extract_done_cbs(&rtpcp->cblist, &rcl);

		raw_spin_unlock_irqrestore_rcu_node(rtpcp, flags);

		len = rcl.len;

		for (rhp = rcu_cblist_dequeue(&rcl); rhp; rhp = rcu_cblist_dequeue(&rcl)) {

			local_bh_disable();

			rhp->func(rhp);

			local_bh_enable();

			cond_resched();

		}

		raw_spin_lock_irqsave_rcu_node(rtpcp, flags);

		rcu_segcblist_add_len(&rtpcp->cblist, -len);

		(void)rcu_segcblist_accelerate(&rtpcp->cblist, rcu_seq_snap(&rtp->tasks_gp_seq));

		raw_spin_unlock_irqrestore_rcu_node(rtpcp, flags);

	}

}



/* RCU-tasks kthread that detects grace periods and invokes callbacks. */

static int __noreturn rcu_tasks_kthread(void *arg)

{

	int needgpcb;

	struct rcu_tasks *rtp = arg;



	/* Run on housekeeping CPUs by default.  Sysadm can move if desired. */
@@ -276,8 +304,6 @@ static int __noreturn rcu_tasks_kthread(void *arg) 
	 * This loop is terminated by the system going down.  ;-)

	 */

	for (;;) {

		struct rcu_tasks_percpu *rtpcp;



		set_tasks_gp_state(rtp, RTGS_WAIT_CBS);



		/* If there were none, wait a bit and start over. */
@@ -292,24 +318,10 @@ static int __noreturn rcu_tasks_kthread(void *arg) 
			rcu_seq_end(&rtp->tasks_gp_seq);

		}



		/* Invoke the callbacks. */

		/* Invoke callbacks. */

		set_tasks_gp_state(rtp, RTGS_INVOKE_CBS);

		rtpcp = per_cpu_ptr(rtp->rtpcpu, 0);

		raw_spin_lock_irqsave_rcu_node(rtpcp, flags);

		rcu_segcblist_advance(&rtpcp->cblist, rcu_seq_current(&rtp->tasks_gp_seq));

		rcu_segcblist_extract_done_cbs(&rtpcp->cblist, &rcl);

		raw_spin_unlock_irqrestore_rcu_node(rtpcp, flags);

		len = rcl.len;

		for (rhp = rcu_cblist_dequeue(&rcl); rhp; rhp = rcu_cblist_dequeue(&rcl)) {

			local_bh_disable();

			rhp->func(rhp);

			local_bh_enable();

			cond_resched();

		}

		raw_spin_lock_irqsave_rcu_node(rtpcp, flags);

		rcu_segcblist_add_len(&rtpcp->cblist, -len);

		(void)rcu_segcblist_accelerate(&rtpcp->cblist, rcu_seq_snap(&rtp->tasks_gp_seq));

		raw_spin_unlock_irqrestore_rcu_node(rtpcp, flags);

		rcu_tasks_invoke_cbs(rtp);



		/* Paranoid sleep to keep this from entering a tight loop */

		schedule_timeout_idle(rtp->gp_sleep);

	}