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can: bcm: use call_rcu() instead of costly synchronize_rcu()

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In commit d5f9023fa6 ("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 181d444790 ("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: d5f9023fa6 ("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>
This commit is contained in:
Oliver Hartkopp 2022-05-20 20:32:39 +02:00 committed by Marc Kleine-Budde
parent 280e3a857d
commit f1b4e32aca
1 changed files with 14 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
net/can/bcm.c
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@ -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 */
}