The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From f1b4e32aca0811aa011c76e5d6cf2fa19224b386 Mon Sep 17 00:00:00 2001 From: Oliver Hartkopp socketcan@hartkopp.net Date: Fri, 20 May 2022 20:32:39 +0200 Subject: [PATCH] can: bcm: use call_rcu() instead of costly synchronize_rcu()

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: Oliver Hartkopp socketcan@hartkopp.net Signed-off-by: Marc Kleine-Budde mkl@pengutronix.de

diff --git a/net/can/bcm.c b/net/can/bcm.c index 65ee1b784a30..e60161bec850 100644 --- a/net/can/bcm.c +++ b/net/can/bcm.c @@ -100,6 +100,7 @@ static inline u64 get_u64(const struct canfd_frame *cp, int offset)

struct bcm_op { struct list_head list; + struct rcu_head rcu; int ifindex; canid_t can_id; u32 flags; @@ -718,10 +719,9 @@ static struct bcm_op *bcm_find_op(struct list_head *ops, 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); - hrtimer_cancel(&op->thrtimer); + struct bcm_op *op = container_of(rcu_head, struct bcm_op, rcu);

if ((op->frames) && (op->frames != &op->sframe)) kfree(op->frames); @@ -732,6 +732,14 @@ static void bcm_remove_op(struct bcm_op *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) { if (op->rx_reg_dev == dev) { @@ -757,6 +765,9 @@ 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) && (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 * problems) can_rx_unregister() is always a save @@ -785,7 +796,6 @@ static int bcm_delete_rx_op(struct list_head *ops, struct bcm_msg_head *mh, bcm_rx_handler, op);

list_del(&op->list); - synchronize_rcu(); bcm_remove_op(op); return 1; /* done */ }