netdev - Re: Hangs in r8152 connected to power management in kernels at least up v4.17-rc4

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Date:   Fri, 25 May 2018 10:41:37 +0200
From:   Jiri Slaby <jslaby@...e.cz>
To:     Hayes Wang <hayeswang@...ltek.com>,
        Oliver Neukum <ONeukum@...e.com>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: Hangs in r8152 connected to power management in kernels at least
 up v4.17-rc4

On 05/16/2018, 03:36 PM, Jiri Slaby wrote:
> So I assume it must be a problem of making usb->disconnect without prior
> ndo->close (or alike).

So according to my debug messages, I think this should workaround the
problem:
--- a/drivers/net/usb/r8152.c
+++ b/drivers/net/usb/r8152.c
@@ -3962,7 +3962,8 @@ static int rtl8152_close(struct net_device *netdev)
 #ifdef CONFIG_PM_SLEEP
        unregister_pm_notifier(&tp->pm_notifier);
 #endif
-       napi_disable(&tp->napi);
+       if (!test_bit(RTL8152_UNPLUG, &tp->flags))
+               napi_disable(&tp->napi);
        clear_bit(WORK_ENABLE, &tp->flags);
        usb_kill_urb(tp->intr_urb);
        cancel_delayed_work_sync(&tp->schedule);


napi is deleted in usb->disconnect, then unregister_netdev is called
which invokes netdev->ndo_stop, i.e. rtl8152_close above. And
rtl8152_close tries to napi_disable, but that is already deleted.

The patch does not solve the race between disconnect and ndo_stop
AFAICS. It needs locking, IMO. I am not familiar enough with the code,
but it looks like ->disconnect can happen any time while ->stop is in
progress.

thanks,
-- 
js
suse labs