Commit 381a4f3b authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu-tasks: Use spin_lock_rcu_node() and friends 



This commit renames the rcu_tasks_percpu structure's ->cbs_pcpu_lock
to ->lock and then uses spin_lock_rcu_node() and friends to acquire and
release this lock, preparing for upcoming commits that will spread the
grace-period process across multiple CPUs and kthreads.

[ paulmck: Apply feedback from kernel test robot. ]

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 9b073de1

kernel/rcu/tasks.h

+20 −22
Original line number Diff line number Diff line
@@ -23,11 +23,11 @@ typedef void (*postgp_func_t)(struct rcu_tasks *rtp); 
/**

 * struct rcu_tasks_percpu - Per-CPU component of definition for a Tasks-RCU-like mechanism.

 * @cblist: Callback list.

 * @cbs_pcpu_lock: Lock protecting per-CPU callback list.

 * @lock: Lock protecting per-CPU callback list.

 */

struct rcu_tasks_percpu {

	struct rcu_segcblist cblist;

	raw_spinlock_t cbs_pcpu_lock;

	raw_spinlock_t __private lock;

};



/**
@@ -82,7 +82,7 @@ struct rcu_tasks { 


#define DEFINE_RCU_TASKS(rt_name, gp, call, n)						\

static DEFINE_PER_CPU(struct rcu_tasks_percpu, rt_name ## __percpu) = {			\

	.cbs_pcpu_lock = __RAW_SPIN_LOCK_UNLOCKED(rt_name ## __percpu.cbs_pcpu_lock),	\

	.lock = __RAW_SPIN_LOCK_UNLOCKED(rt_name ## __percpu.cbs_pcpu_lock),		\

};											\

static struct rcu_tasks rt_name =							\

{											\
@@ -177,11 +177,11 @@ static void cblist_init_generic(struct rcu_tasks *rtp) 


		WARN_ON_ONCE(!rtpcp);

		if (cpu)

			raw_spin_lock_init(&rtpcp->cbs_pcpu_lock);

		raw_spin_lock(&rtpcp->cbs_pcpu_lock); // irqs already disabled.

			raw_spin_lock_init(&ACCESS_PRIVATE(rtpcp, lock));

		raw_spin_lock_rcu_node(rtpcp); // irqs already disabled.

		if (rcu_segcblist_empty(&rtpcp->cblist))

			rcu_segcblist_init(&rtpcp->cblist);

		raw_spin_unlock(&rtpcp->cbs_pcpu_lock); // irqs remain disabled.

		raw_spin_unlock_rcu_node(rtpcp); // irqs remain disabled.

	}

	raw_spin_unlock_irqrestore(&rtp->cbs_gbl_lock, flags);
@@ -200,15 +200,15 @@ static void call_rcu_tasks_generic(struct rcu_head *rhp, rcu_callback_t func, 
	local_irq_save(flags);

	rtpcp = per_cpu_ptr(rtp->rtpcpu,

			    smp_processor_id() >> READ_ONCE(rtp->percpu_enqueue_shift));

	raw_spin_lock(&rtpcp->cbs_pcpu_lock);

	raw_spin_lock_rcu_node(rtpcp); // irqs already disabled.

	if (!rcu_segcblist_is_enabled(&rtpcp->cblist)) {

		raw_spin_unlock(&rtpcp->cbs_pcpu_lock); // irqs remain disabled.

		raw_spin_unlock_rcu_node(rtpcp); // irqs remain disabled.

		cblist_init_generic(rtp);

		raw_spin_lock(&rtpcp->cbs_pcpu_lock); // irqs already disabled.

		raw_spin_lock_rcu_node(rtpcp); // irqs already disabled.

	}

	needwake = rcu_segcblist_empty(&rtpcp->cblist);

	rcu_segcblist_enqueue(&rtpcp->cblist, rhp);

	raw_spin_unlock_irqrestore(&rtpcp->cbs_pcpu_lock, flags);

	raw_spin_unlock_irqrestore_rcu_node(rtpcp, flags);

	/* We can't create the thread unless interrupts are enabled. */

	if (needwake && READ_ONCE(rtp->kthread_ptr))

		wake_up(&rtp->cbs_wq);
@@ -250,11 +250,10 @@ static int __noreturn rcu_tasks_kthread(void *arg) 
		set_tasks_gp_state(rtp, RTGS_WAIT_CBS);



		/* Pick up any new callbacks. */

		raw_spin_lock_irqsave(&rtpcp->cbs_pcpu_lock, flags);

		smp_mb__after_spinlock(); // Order updates vs. GP.

		raw_spin_lock_irqsave_rcu_node(rtpcp, flags);

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

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

		raw_spin_unlock_irqrestore(&rtpcp->cbs_pcpu_lock, flags);

		raw_spin_unlock_irqrestore_rcu_node(rtpcp, flags);



		/* If there were none, wait a bit and start over. */

		if (!rcu_segcblist_pend_cbs(&rtpcp->cblist)) {
@@ -277,11 +276,10 @@ static int __noreturn rcu_tasks_kthread(void *arg) 


		/* Invoke the callbacks. */

		set_tasks_gp_state(rtp, RTGS_INVOKE_CBS);

		raw_spin_lock_irqsave(&rtpcp->cbs_pcpu_lock, flags);

		smp_mb__after_spinlock(); // Order updates vs. GP.

		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(&rtpcp->cbs_pcpu_lock, flags);

		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();
@@ -289,10 +287,10 @@ static int __noreturn rcu_tasks_kthread(void *arg) 
			local_bh_enable();

			cond_resched();

		}

		raw_spin_lock_irqsave(&rtpcp->cbs_pcpu_lock, flags);

		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(&rtpcp->cbs_pcpu_lock, flags);

		raw_spin_unlock_irqrestore_rcu_node(rtpcp, flags);

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

		schedule_timeout_idle(rtp->gp_sleep);

	}
@@ -470,10 +468,10 @@ static void rcu_tasks_wait_gp(struct rcu_tasks *rtp) 
// exit_tasks_rcu_finish() functions begin and end, respectively, the SRCU

// read-side critical sections waited for by rcu_tasks_postscan().

//

// Pre-grace-period update-side code is ordered before the grace via the

// ->cbs_lock and the smp_mb__after_spinlock().  Pre-grace-period read-side

// code is ordered before the grace period via synchronize_rcu() call

// in rcu_tasks_pregp_step() and by the scheduler's locks and interrupt

// Pre-grace-period update-side code is ordered before the grace

// via the raw_spin_lock.*rcu_node().  Pre-grace-period read-side code

// is ordered before the grace period via synchronize_rcu() call in

// rcu_tasks_pregp_step() and by the scheduler's locks and interrupt

// disabling.



/* Pre-grace-period preparation. */