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From: David Miller <davem@davemloft.net>
To: Jan.Kloetzke@preh.de
Cc: oneukum@suse.com, netdev@vger.kernel.org, jan@kloetzke.net,
	linux-usb@vger.kernel.org
Subject: Re: [PATCH] usbnet: fix kernel crash after disconnect
Date: Thu, 18 Apr 2019 16:35:44 -0700 (PDT)	[thread overview]
Message-ID: <20190418.163544.2153438649838575906.davem@davemloft.net> (raw)
In-Reply-To: <1555574578.4173.215.camel@preh.de>

From: Kloetzke Jan <Jan.Kloetzke@preh.de>
Date: Thu, 18 Apr 2019 08:02:59 +0000

> I think this assumption is not correct. As far as I understand the
> networking code it is still possible that the ndo_start_xmit callback
> is called while ndo_stop is running and even after ndo_stop has
> returned. You can only be sure after unregister_netdev() has returned.
> Maybe some networking folks can comment on that.

The kernel loops over the devices being unregistered, and first it clears
the __LINK_STATE_START on all of them, then it invokes ->ndo_stop() on
all of them.

__LINK_STATE_START controls what netif_running() returns.

All calls to ->ndo_start_xmit() are guarded by netif_running() checks.

So when ndo_stop is invoked you should get no more ndo_start_xmit
invocations on that device.  Otherwise how could you shut down DMA
resources and turn off the TX engine properly?

  reply	other threads:[~2019-04-18 23:35 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-17  9:19 [PATCH] usbnet: fix kernel crash after disconnect Kloetzke Jan
2019-04-18  6:37 ` Oliver Neukum
2019-04-18  8:02   ` Kloetzke Jan
2019-04-18 23:35     ` David Miller [this message]
2019-04-19  7:17       ` Jan Klötzke
2019-04-29 18:48         ` Oliver Neukum
2019-04-30 14:08           ` Kloetzke Jan
2019-04-30 14:15           ` [PATCH v2] " Kloetzke Jan
2019-05-05  7:45             ` David Miller
2019-05-06  8:17               ` Oliver Neukum
2019-05-16  7:10                 ` Kloetzke Jan
2019-05-21  0:09                   ` David Miller
2019-05-21  9:48                   ` Oliver Neukum
2019-05-21 10:12                     ` Kloetzke Jan
2019-05-21 11:42                       ` Oliver Neukum
2019-05-21 13:18                         ` [PATCH v3] " Kloetzke Jan
2019-05-21 20:47                           ` David Miller

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