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Commit bdcabf4c authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu: Add single-element dequeue functions to rcu_segcblist 



This commit adds single-element dequeue functions to rcu_segcblist.
These are less efficient than using the extract and insert functions,
but allow more precise debugging code.  These functions are thus
expected to be used only in debug builds, for example, CONFIG_PROVE_RCU.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent b5eaeaa5

kernel/rcu/rcu_segcblist.h

+45 −0
Original line number Diff line number Diff line
@@ -289,6 +289,51 @@ static inline bool rcu_segcblist_pend_cbs(struct rcu_segcblist *rsclp) 
	       !rcu_segcblist_restempty(rsclp, RCU_DONE_TAIL);

}



/*

 * Dequeue and return the first ready-to-invoke callback.  If there

 * are no ready-to-invoke callbacks, return NULL.  Disables interrupts

 * to avoid interference.  Does not protect from interference from other

 * CPUs or tasks.

 */

static inline struct rcu_head *

rcu_segcblist_dequeue(struct rcu_segcblist *rsclp)

{

	unsigned long flags;

	int i;

	struct rcu_head *rhp;



	local_irq_save(flags);

	if (!rcu_segcblist_ready_cbs(rsclp)) {

		local_irq_restore(flags);

		return NULL;

	}

	rhp = rsclp->head;

	BUG_ON(!rhp);

	rsclp->head = rhp->next;

	for (i = RCU_DONE_TAIL; i < RCU_CBLIST_NSEGS; i++) {

		if (rsclp->tails[i] != &rhp->next)

			break;

		rsclp->tails[i] = &rsclp->head;

	}

	smp_mb(); /* Dequeue before decrement for rcu_barrier(). */

	WRITE_ONCE(rsclp->len, rsclp->len - 1);

	local_irq_restore(flags);

	return rhp;

}



/*

 * Account for the fact that a previously dequeued callback turned out

 * to be marked as lazy.

 */

static inline void rcu_segcblist_dequeued_lazy(struct rcu_segcblist *rsclp)

{

	unsigned long flags;



	local_irq_save(flags);

	rsclp->len_lazy--;

	local_irq_restore(flags);

}



/*

 * Return a pointer to the first callback in the specified rcu_segcblist

 * structure.  This is useful for diagnostics.