| Message ID | 20220214234814.1321599-1-mailhol.vincent@wanadoo.fr (mailing list archive) |
|---|---|
| State | RFC |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [RFC,v1] can: gs_usb: change active_channels's type from atomic_t to u8 | expand |
| Context | Check | Description |
|---|---|---|
| netdev/tree_selection | success | Series ignored based on subject |
On 15.02.2022 08:48:14, Vincent Mailhol wrote: > The driver uses an atomic_t variable: gs_usb:active_channels to keep > track of the number of opened channels in order to only allocate > memory for the URBs when this count changes from zero to one. > > However, the driver does not decrement the counter when an error > occurs in gs_can_open(). This issue is fixed by changing the type from > atomic_t to u8 and by simplifying the logic accordingly. > > It is safe to use an u8 here because the network stack big kernel lock > (a.k.a. rtnl_mutex) is being hold. For details, please refer to [1]. > > [1] https://lore.kernel.org/linux-can/CAMZ6Rq+sHpiw34ijPsmp7vbUpDtJwvVtdV7CvRZJsLixjAFfrg@mail.gmail.com/T/#t > > Fixes: d08e973a77d1 ("can: gs_usb: Added support for the GS_USB CAN > devices") > Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr> Looks good to me, added to linux-can/testing. regards, Marc
diff --git a/drivers/net/can/usb/gs_usb.c b/drivers/net/can/usb/gs_usb.c index b487e3fe770a..d35749fad1ef 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);
The driver uses an atomic_t variable: gs_usb:active_channels to keep track of the number of opened channels in order to only allocate memory for the URBs when this count changes from zero to one. However, the driver does not decrement the counter when an error occurs in gs_can_open(). This issue is fixed by changing the type from atomic_t to u8 and by simplifying the logic accordingly. It is safe to use an u8 here because the network stack big kernel lock (a.k.a. rtnl_mutex) is being hold. For details, please refer to [1]. [1] https://lore.kernel.org/linux-can/CAMZ6Rq+sHpiw34ijPsmp7vbUpDtJwvVtdV7CvRZJsLixjAFfrg@mail.gmail.com/T/#t Fixes: d08e973a77d1 ("can: gs_usb: Added support for the GS_USB CAN devices") Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr> --- drivers/net/can/usb/gs_usb.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-)