On Sat, Jun 15, 2024 at 01:45:56AM +0300, Dmitry Smirnov wrote:
> This patch addresses a kernel hang issue with the mos7840 driver when
> PC resuming from a suspend with a device connected to the serial port.
>
> This patch introduces two new functions: mos7840_suspend() and mos7840_resume().
>
> Tested with Delock 87414 USB 2.0 to 4x serial adapter.
>
> Signed-off-by: Dmitry Smirnov <d.smirnov@xxxxxxxx>
> ---
> V4: Removed debug prints
> V3: Code cleanup
> V2: Reworked mos7840_suspend() based on comments from reviewer
> V1: Initial version
Thanks for the fix and sorry about the late reply on this one.
I took a closer look at this today, and indeed we have a kernel crash
here on resume with mos7840. This is a bug that dates back to 2011 when
I added support for multiple read URBs and failed to notice this
interaction with drivers that only uses one URB.
This actually affects a few more drivers, but judging from a quick look
not as severely as for mos7840 which uses a different structure for the
URB context. I'll make sure to go back and review this more thoroughly
in the next few weeks.
> +static int mos7840_resume(struct usb_serial *serial)
> +{
> + struct moschip_port *mos7840_port;
> + struct usb_serial_port *port;
> + int res;
> + int i;
> +
> + for (i = 0; i < serial->num_ports; ++i) {
> + port = serial->port[i];
> + if (!tty_port_initialized(&port->port))
> + continue;
> +
> + mos7840_port = usb_get_serial_port_data(port);
> +
> + if (port->bulk_in_size) {
Not needed, checked on probe.
Need to set the read_urb_busy flag here.
> + res = usb_submit_urb(mos7840_port->read_urb, GFP_NOIO);
> + if (res) {
> + usb_kill_urb(mos7840_port->read_urb);
Not needed as submission failed.
> + mos7840_port->read_urb_busy = false;
> + }
> + }
> + }
> +
> + return 0;
> +}
I've reworded the commit message to provide some more background on the
crash, added the missing busy flag set, dropped the unnecessary
bulk_in_size check and dropped the unnecessary usb_kill_urb() in case
submission fails on resume.
The end result is here:
https://git.kernel.org/pub/scm/linux/kernel/git/johan/usb-serial.git/commit/?h=usb-linus&id=c15a688e49987385baa8804bf65d570e362f8576
Johan
