diff mbox series

[net-next,1/2] r8152: If inaccessible at resume time, issue a reset

Message ID 20240520134108.net-next.1.Ibeda5c0772812ce18953150da5a0888d2d875150@changeid
State Superseded
Headers show
Series [net-next,1/2] r8152: If inaccessible at resume time, issue a reset | expand

Commit Message

Doug Anderson May 20, 2024, 8:41 p.m. UTC
If we happened to get a USB transfer error during the transition to
suspend then the usb_queue_reset_device() that r8152_control_msg()
calls will get dropped on the floor. This is because
usb_lock_device_for_reset() (which usb_queue_reset_device() uses)
silently fails if it's called when a device is suspended or if too
much time passes.

Let's resolve this by resetting the device ourselves in r8152's
resume() function.

NOTE: due to timing, it's _possible_ that we could end up with two USB
resets: the one queued previously and the one called from the resume()
patch. This didn't happen in test cases I ran, though it's conceivably
possible. We can't easily know if this happened since
usb_queue_reset_device() can just silently drop the reset request. In
any case, it's not expected that this is a problem since the two
resets can't run at the same time (because of the device lock) and it
should be OK to reset the device twice. If somehow the double-reset
causes problems we could prevent resets from being queued up while
suspend is running.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
---

 drivers/net/usb/r8152.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

Comments

Paolo Abeni May 21, 2024, 9:13 a.m. UTC | #1
On Mon, 2024-05-20 at 13:41 -0700, Douglas Anderson wrote:
> If we happened to get a USB transfer error during the transition to
> suspend then the usb_queue_reset_device() that r8152_control_msg()
> calls will get dropped on the floor. This is because
> usb_lock_device_for_reset() (which usb_queue_reset_device() uses)
> silently fails if it's called when a device is suspended or if too
> much time passes.
> 
> Let's resolve this by resetting the device ourselves in r8152's
> resume() function.
> 
> NOTE: due to timing, it's _possible_ that we could end up with two USB
> resets: the one queued previously and the one called from the resume()
> patch. This didn't happen in test cases I ran, though it's conceivably
> possible. We can't easily know if this happened since
> usb_queue_reset_device() can just silently drop the reset request. In
> any case, it's not expected that this is a problem since the two
> resets can't run at the same time (because of the device lock) and it
> should be OK to reset the device twice. If somehow the double-reset
> causes problems we could prevent resets from being queued up while
> suspend is running.
> 
> Signed-off-by: Douglas Anderson <dianders@chromium.org>

## Form letter - net-next-closed

The merge window for v6.10 has begun and we have already posted our
pull
request. Therefore net-next is closed for new drivers, features, code
refactoring and optimizations. We are currently accepting bug fixes
only.

Please repost when net-next reopens after May 26th.

RFC patches sent for review only are obviously welcome at any time.

See:
https://www.kernel.org/doc/html/next/process/maintainer-netdev.html#development-cycle
diff mbox series

Patch

diff --git a/drivers/net/usb/r8152.c b/drivers/net/usb/r8152.c
index 19df1cd9f072..6a3f4b2114ee 100644
--- a/drivers/net/usb/r8152.c
+++ b/drivers/net/usb/r8152.c
@@ -8554,6 +8554,19 @@  static int rtl8152_system_resume(struct r8152 *tp)
 		usb_submit_urb(tp->intr_urb, GFP_NOIO);
 	}
 
+	/* If the device is RTL8152_INACCESSIBLE here then we should do a
+	 * reset. This is important because the usb_lock_device_for_reset()
+	 * that happens as a result of usb_queue_reset_device() will silently
+	 * fail if the device was suspended or if too much time passed.
+	 *
+	 * NOTE: The device is locked here so we can directly do the reset.
+	 * We don't need usb_lock_device_for_reset() because that's just a
+	 * wrapper over device_lock() and device_resume() (which calls us)
+	 * does that for us.
+	 */
+	if (test_bit(RTL8152_INACCESSIBLE, &tp->flags))
+		usb_reset_device(tp->udev);
+
 	return 0;
 }