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Commit b41772ab authored by Paul E. McKenney's avatar Paul E. McKenney Committed by Paul E. McKenney
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rcu: Stop rcu_do_batch() from multiplexing the "count" variable 



Commit b1420f1c (Make rcu_barrier() less disruptive) rearranged the
code in rcu_do_batch(), moving the ->qlen manipulation to follow
the requeueing of the callbacks.  Unfortunately, this rearrangement
clobbered the value of the "count" local variable before the value
of rdp->qlen was adjusted, resulting in the value of rdp->qlen being
inaccurate.  This commit therefore introduces an index variable "i",
avoiding the inadvertent multiplexing.

Signed-off-by: default avatarPaul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: default avatarJosh Triplett <josh@joshtriplett.org>
parent 6b16351a

kernel/rcutree.c

+7 −7
Original line number Diff line number Diff line
@@ -1530,7 +1530,7 @@ static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp) 
{

	unsigned long flags;

	struct rcu_head *next, *list, **tail;

	int bl, count, count_lazy;

	int bl, count, count_lazy, i;



	/* If no callbacks are ready, just return.*/

	if (!cpu_has_callbacks_ready_to_invoke(rdp)) {
@@ -1553,9 +1553,9 @@ static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp) 
	rdp->nxtlist = *rdp->nxttail[RCU_DONE_TAIL];

	*rdp->nxttail[RCU_DONE_TAIL] = NULL;

	tail = rdp->nxttail[RCU_DONE_TAIL];

	for (count = RCU_NEXT_SIZE - 1; count >= 0; count--)

		if (rdp->nxttail[count] == rdp->nxttail[RCU_DONE_TAIL])

			rdp->nxttail[count] = &rdp->nxtlist;

	for (i = RCU_NEXT_SIZE - 1; i >= 0; i--)

		if (rdp->nxttail[i] == rdp->nxttail[RCU_DONE_TAIL])

			rdp->nxttail[i] = &rdp->nxtlist;

	local_irq_restore(flags);



	/* Invoke callbacks. */
@@ -1583,9 +1583,9 @@ static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp) 
	if (list != NULL) {

		*tail = rdp->nxtlist;

		rdp->nxtlist = list;

		for (count = 0; count < RCU_NEXT_SIZE; count++)

			if (&rdp->nxtlist == rdp->nxttail[count])

				rdp->nxttail[count] = tail;

		for (i = 0; i < RCU_NEXT_SIZE; i++)

			if (&rdp->nxtlist == rdp->nxttail[i])

				rdp->nxttail[i] = tail;

			else

				break;

	}