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USB: hub: Fix handling of connect changes during sleep

Browse source 
commit 9f952e26295d977dbfc6fedeaf8c4f112c818d37 upstream.

Commit 8099f58f1ecd ("USB: hub: Don't record a connect-change event
during reset-resume") wasn't very well conceived.  The problem it
tried to fix was that if a connect-change event occurred while the
system was asleep (such as a device disconnecting itself from the bus
when it is suspended and then reconnecting when it resumes)
requiring a reset-resume during the system wakeup transition, the hub
port's change_bit entry would remain set afterward.  This would cause
the hub driver to believe another connect-change event had occurred
after the reset-resume, which was wrong and would lead the driver to
send unnecessary requests to the device (which could interfere with a
firmware update).

The commit tried to fix this by not setting the change_bit during the
wakeup.  But this was the wrong thing to do; it means that when a
device is unplugged while the system is asleep, the hub driver doesn't
realize anything has happened: The change_bit flag which would tell it
to handle the disconnect event is clear.

The commit needs to be reverted and the problem fixed in a different
way.  Fortunately an alternative solution was noted in the commit's
Changelog: We can continue to set the change_bit entry in
hub_activate() but then clear it when a reset-resume occurs.  That way
the the hub driver will see the change_bit when a device is
disconnected but won't see it when the device is still present.

That's what this patch does.

Reported-and-tested-by: Peter Chen <[email protected]>
Signed-off-by: Alan Stern <[email protected]>
Fixes: 8099f58f1ecd ("USB: hub: Don't record a connect-change event during reset-resume")
Tested-by: Paul Zimmerman <[email protected]>
CC: <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>
This commit is contained in:
Alan Stern 2020-04-22 16:09:51 -04:00 • committed by Greg Kroah-Hartman
commit 50ad463e20
1 changed files with 14 additions and 0 deletions
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14
drivers/usb/core/hub.c
View file

@ -1222,6 +1222,11 @@ static void hub_activate(struct usb_hub *hub, enum hub_activation_type type)
#ifdef CONFIG_PM
udev->reset_resume = 1;
#endif
/* Don't set the change_bits when the device
* was powered off.
*/
if (test_bit(port1, hub->power_bits))
set_bit(port1, hub->change_bits);
} else {
/* The power session is gone; tell hub_wq */
@ -3087,6 +3092,15 @@ static int check_port_resume_type(struct usb_device *udev,
if (portchange & USB_PORT_STAT_C_ENABLE)
usb_clear_port_feature(hub->hdev, port1,
USB_PORT_FEAT_C_ENABLE);
/*
* Whatever made this reset-resume necessary may have
* turned on the port1 bit in hub->change_bits. But after
* a successful reset-resume we want the bit to be clear;
* if it was on it would indicate that something happened
* following the reset-resume.
*/
clear_bit(port1, hub->change_bits);
}
return status;