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Commit fbac09a3 authored by Oliver Hartkopp's avatar Oliver Hartkopp Committed by Greg Kroah-Hartman
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can: bcm: use call_rcu() instead of costly synchronize_rcu() 

commit f1b4e32aca0811aa011c76e5d6cf2fa19224b386 upstream.

In commit d5f9023fa61e ("can: bcm: delay release of struct bcm_op
after synchronize_rcu()") Thadeu Lima de Souza Cascardo introduced two
synchronize_rcu() calls in bcm_release() (only once at socket close)
and in bcm_delete_rx_op() (called on removal of each single bcm_op).

Unfortunately this slow removal of the bcm_op's affects user space
applications like cansniffer where the modification of a filter
removes 2048 bcm_op's which blocks the cansniffer application for
40(!) seconds.

In commit 181d4447905d ("can: gw: use call_rcu() instead of costly
synchronize_rcu()") Eric Dumazet replaced the synchronize_rcu() calls
with several call_rcu()'s to safely remove the data structures after
the removal of CAN ID subscriptions with can_rx_unregister() calls.

This patch adopts Erics approach for the can-bcm which should be
applicable since the removal of tasklet_kill() in bcm_remove_op() and
the introduction of the HRTIMER_MODE_SOFT timer handling in Linux 5.4.

Fixes: d5f9023fa61e ("can: bcm: delay release of struct bcm_op after synchronize_rcu()") # >= 5.4
Link: https://lore.kernel.org/all/20220520183239.19111-1-socketcan@hartkopp.net


Cc: stable@vger.kernel.org
Cc: Eric Dumazet <edumazet@google.com>
Cc: Norbert Slusarek <nslusarek@gmx.net>
Cc: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Signed-off-by: default avatarOliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: default avatarMarc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent e2b2f0e2

net/can/bcm.c

+14 −4
Original line number Original line Diff line number Diff line
@@ -99,6 +99,7 @@ static inline u64 get_u64(const struct canfd_frame *cp, int offset) 




struct bcm_op {

struct bcm_op {

	struct list_head list;

	struct list_head list;

	struct rcu_head rcu;

	int ifindex;

	int ifindex;

	canid_t can_id;

	canid_t can_id;

	u32 flags;

	u32 flags;
@@ -717,10 +718,9 @@ static struct bcm_op *bcm_find_op(struct list_head *ops, 
	return NULL;

	return NULL;

}

}





static void bcm_remove_op(struct bcm_op *op)

static void bcm_free_op_rcu(struct rcu_head *rcu_head)

{

{

	hrtimer_cancel(&op->timer);

	struct bcm_op *op = container_of(rcu_head, struct bcm_op, rcu);

	hrtimer_cancel(&op->thrtimer);





	if ((op->frames) && (op->frames != &op->sframe))

	if ((op->frames) && (op->frames != &op->sframe))

		kfree(op->frames);

		kfree(op->frames);
@@ -731,6 +731,14 @@ static void bcm_remove_op(struct bcm_op *op) 
	kfree(op);

	kfree(op);

}

}





static void bcm_remove_op(struct bcm_op *op)

{

	hrtimer_cancel(&op->timer);

	hrtimer_cancel(&op->thrtimer);



	call_rcu(&op->rcu, bcm_free_op_rcu);

}



static void bcm_rx_unreg(struct net_device *dev, struct bcm_op *op)

static void bcm_rx_unreg(struct net_device *dev, struct bcm_op *op)

{

{

	if (op->rx_reg_dev == dev) {

	if (op->rx_reg_dev == dev) {
@@ -756,6 +764,9 @@ static int bcm_delete_rx_op(struct list_head *ops, struct bcm_msg_head *mh, 
		if ((op->can_id == mh->can_id) && (op->ifindex == ifindex) &&

		if ((op->can_id == mh->can_id) && (op->ifindex == ifindex) &&

		    (op->flags & CAN_FD_FRAME) == (mh->flags & CAN_FD_FRAME)) {

		    (op->flags & CAN_FD_FRAME) == (mh->flags & CAN_FD_FRAME)) {





			/* disable automatic timer on frame reception */

			op->flags |= RX_NO_AUTOTIMER;



			/*

			/*

			 * Don't care if we're bound or not (due to netdev

			 * Don't care if we're bound or not (due to netdev

			 * problems) can_rx_unregister() is always a save

			 * problems) can_rx_unregister() is always a save
@@ -784,7 +795,6 @@ static int bcm_delete_rx_op(struct list_head *ops, struct bcm_msg_head *mh, 
						  bcm_rx_handler, op);

						  bcm_rx_handler, op);





			list_del(&op->list);

			list_del(&op->list);

			synchronize_rcu();

			bcm_remove_op(op);

			bcm_remove_op(op);

			return 1; /* done */

			return 1; /* done */

		}

		}