Merge tag 'linux-can-fixes-for-5.17-20220225' of git://git.kernel.org/pub/scm/linux/kernel/git/mkl/linux-can

Marc Kleine-Budde says:

====================
pull-request: can 2022-02-25

The first 2 patches are by Vincent Mailhol and fix the error handling
of the ndo_open callbacks of the etas_es58x and the gs_usb CAN USB
drivers.

The last patch is by Lad Prabhakar and fixes a small race condition in
the rcar_canfd's rcar_canfd_channel_probe() function.

* tag 'linux-can-fixes-for-5.17-20220225' of git://git.kernel.org/pub/scm/linux/kernel/git/mkl/linux-can:
  can: rcar_canfd: rcar_canfd_channel_probe(): register the CAN device when fully ready
  can: gs_usb: change active_channels's type from atomic_t to u8
  can: etas_es58x: change opened_channel_cnt's type from atomic_t to u8
====================

Link: https://lore.kernel.org/r/20220225165622.3231809-1-mkl@pengutronix.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

4 files changed, 18 insertions, 15 deletions

diff --git a/drivers/net/can/rcar/rcar_canfd.c b/drivers/net/can/rcar/rcar_canfd.c
index b7dc1c32875f2..acd74725831f2 100644
--- a/drivers/net/can/rcar/rcar_canfd.c
+++ b/drivers/net/can/rcar/rcar_canfd.c
@@ -1715,15 +1715,15 @@ static int rcar_canfd_channel_probe(struct rcar_canfd_global *gpriv, u32 ch,
 
 	netif_napi_add(ndev, &priv->napi, rcar_canfd_rx_poll,
 		       RCANFD_NAPI_WEIGHT);
+	spin_lock_init(&priv->tx_lock);
+	devm_can_led_init(ndev);
+	gpriv->ch[priv->channel] = priv;
 	err = register_candev(ndev);
 	if (err) {
 		dev_err(&pdev->dev,
 			"register_candev() failed, error %d\n", err);
 		goto fail_candev;
 	}
-	spin_lock_init(&priv->tx_lock);
-	devm_can_led_init(ndev);
-	gpriv->ch[priv->channel] = priv;
 	dev_info(&pdev->dev, "device registered (channel %u)\n", priv->channel);
 	return 0;
 
diff --git a/drivers/net/can/usb/etas_es58x/es58x_core.c b/drivers/net/can/usb/etas_es58x/es58x_core.c
index 2ed2370a31667..2d73ebbf38364 100644
--- a/drivers/net/can/usb/etas_es58x/es58x_core.c
+++ b/drivers/net/can/usb/etas_es58x/es58x_core.c
@@ -1787,7 +1787,7 @@ static int es58x_open(struct net_device *netdev)
 	struct es58x_device *es58x_dev = es58x_priv(netdev)->es58x_dev;
 	int ret;
 
-	if (atomic_inc_return(&es58x_dev->opened_channel_cnt) == 1) {
+	if (!es58x_dev->opened_channel_cnt) {
 		ret = es58x_alloc_rx_urbs(es58x_dev);
 		if (ret)
 			return ret;
@@ -1805,12 +1805,13 @@ static int es58x_open(struct net_device *netdev)
 	if (ret)
 		goto free_urbs;
 
+	es58x_dev->opened_channel_cnt++;
 	netif_start_queue(netdev);
 
 	return ret;
 
  free_urbs:
-	if (atomic_dec_and_test(&es58x_dev->opened_channel_cnt))
+	if (!es58x_dev->opened_channel_cnt)
 		es58x_free_urbs(es58x_dev);
 	netdev_err(netdev, "%s: Could not open the network device: %pe\n",
 		   __func__, ERR_PTR(ret));
@@ -1845,7 +1846,8 @@ static int es58x_stop(struct net_device *netdev)
 
 	es58x_flush_pending_tx_msg(netdev);
 
-	if (atomic_dec_and_test(&es58x_dev->opened_channel_cnt))
+	es58x_dev->opened_channel_cnt--;
+	if (!es58x_dev->opened_channel_cnt)
 		es58x_free_urbs(es58x_dev);
 
 	return 0;
@@ -2215,7 +2217,6 @@ static struct es58x_device *es58x_init_es58x_dev(struct usb_interface *intf,
 	init_usb_anchor(&es58x_dev->tx_urbs_idle);
 	init_usb_anchor(&es58x_dev->tx_urbs_busy);
 	atomic_set(&es58x_dev->tx_urbs_idle_cnt, 0);
-	atomic_set(&es58x_dev->opened_channel_cnt, 0);
 	usb_set_intfdata(intf, es58x_dev);
 
 	es58x_dev->rx_pipe = usb_rcvbulkpipe(es58x_dev->udev,
diff --git a/drivers/net/can/usb/etas_es58x/es58x_core.h b/drivers/net/can/usb/etas_es58x/es58x_core.h
index 826a15871573a..e5033cb5e6959 100644
--- a/drivers/net/can/usb/etas_es58x/es58x_core.h
+++ b/drivers/net/can/usb/etas_es58x/es58x_core.h
@@ -373,8 +373,6 @@ struct es58x_operators {
  *	queue wake/stop logic should prevent this URB from getting
  *	empty. Please refer to es58x_get_tx_urb() for more details.
  * @tx_urbs_idle_cnt: number of urbs in @tx_urbs_idle.
- * @opened_channel_cnt: number of channels opened (c.f. es58x_open()
- *	and es58x_stop()).
  * @ktime_req_ns: kernel timestamp when es58x_set_realtime_diff_ns()
  *	was called.
  * @realtime_diff_ns: difference in nanoseconds between the clocks of
@@ -384,6 +382,10 @@ struct es58x_operators {
  *	in RX branches.
  * @rx_max_packet_size: Maximum length of bulk-in URB.
  * @num_can_ch: Number of CAN channel (i.e. number of elements of @netdev).
+ * @opened_channel_cnt: number of channels opened. Free of race
+ *	conditions because its two users (net_device_ops:ndo_open()
+ *	and net_device_ops:ndo_close()) guarantee that the network
+ *	stack big kernel lock (a.k.a. rtnl_mutex) is being hold.
  * @rx_cmd_buf_len: Length of @rx_cmd_buf.
  * @rx_cmd_buf: The device might split the URB commands in an
  *	arbitrary amount of pieces. This buffer is used to concatenate
@@ -406,7 +408,6 @@ struct es58x_device {
 	struct usb_anchor tx_urbs_busy;
 	struct usb_anchor tx_urbs_idle;
 	atomic_t tx_urbs_idle_cnt;
-	atomic_t opened_channel_cnt;
 
 	u64 ktime_req_ns;
 	s64 realtime_diff_ns;
@@ -415,6 +416,7 @@ struct es58x_device {
 
 	u16 rx_max_packet_size;
 	u8 num_can_ch;
+	u8 opened_channel_cnt;
 
 	u16 rx_cmd_buf_len;
 	union es58x_urb_cmd rx_cmd_buf;
diff --git a/drivers/net/can/usb/gs_usb.c b/drivers/net/can/usb/gs_usb.c
index b487e3fe770ae..d35749fad1efa 100644
--- a/drivers/net/can/usb/gs_usb.c
+++ b/drivers/net/can/usb/gs_usb.c
@@ -191,8 +191,8 @@ struct gs_can {
 struct gs_usb {
 	struct gs_can *canch[GS_MAX_INTF];
 	struct usb_anchor rx_submitted;
-	atomic_t active_channels;
 	struct usb_device *udev;
+	u8 active_channels;
 };
 
 /* 'allocate' a tx context.
@@ -589,7 +589,7 @@ static int gs_can_open(struct net_device *netdev)
 	if (rc)
 		return rc;
 
-	if (atomic_add_return(1, &parent->active_channels) == 1) {
+	if (!parent->active_channels) {
 		for (i = 0; i < GS_MAX_RX_URBS; i++) {
 			struct urb *urb;
 			u8 *buf;
@@ -690,6 +690,7 @@ static int gs_can_open(struct net_device *netdev)
 
 	dev->can.state = CAN_STATE_ERROR_ACTIVE;
 
+	parent->active_channels++;
 	if (!(dev->can.ctrlmode & CAN_CTRLMODE_LISTENONLY))
 		netif_start_queue(netdev);
 
@@ -705,7 +706,8 @@ static int gs_can_close(struct net_device *netdev)
 	netif_stop_queue(netdev);
 
 	/* Stop polling */
-	if (atomic_dec_and_test(&parent->active_channels))
+	parent->active_channels--;
+	if (!parent->active_channels)
 		usb_kill_anchored_urbs(&parent->rx_submitted);
 
 	/* Stop sending URBs */
@@ -984,8 +986,6 @@ static int gs_usb_probe(struct usb_interface *intf,
 
 	init_usb_anchor(&dev->rx_submitted);
 
-	atomic_set(&dev->active_channels, 0);
-
 	usb_set_intfdata(intf, dev);
 	dev->udev = interface_to_usbdev(intf);