Messages in this thread | | | Date | Mon, 04 Feb 2013 20:17:04 +0100 | From | Alexander Holler <> | Subject | Re: [PATCH 2/3 v2] fb: udlfb: fix hang at disconnect |
| |
Am 04.02.2013 13:05, schrieb Alexander Holler: > Am 04.02.2013 02:14, schrieb Greg KH: > >> So you are right in that your driver will wait for forever for a >> disconnect() to happen, as it will never be called. I don't understand >> the problem that this is causing when it happens. What's wrong with >> udlfb that having the cpu suddently reset as the powerdown happened >> without it knowing about it? > > There is nothing wrong with that. I've just explained why a problem > doesn't occur on shutdown but on disconnect (of the device).
Maybe my explanation before was just to long and I try to explain it a bit shorter:
If a device gets disconnected, the disconnect in udlfb might wait forever in down_interruptible() (because it waits for an urb it never receives). This even prevents a shutdown afterwards, because that down_interruptible() never receives a signal (at shutdown, because kernel threads don't get such).
So the change from down_timeout() to down_interruptible() in dlfb_free_urb_list() with commit 33077b8d3042e01da61924973e372abe589ba297 only results in that the following code (thus the break there) will never be reached if an urb got missed (because of a disconnect).
And the accompanying comment (... at shutdown) is misleading, because on shutdown, the kernel thread which calls dlfb_free_urb_list() never gets a signal, so the interruption just never happens.
As I've experienced the "missing urb on disconnect" problem quiet often, I've changed that down_interruptible() to down_timeout() (in v1 and in v2 to down_timeout_interruptible, because I wasn't aware that no signal arrives on shutdown).
Hmm, ok, that explanation isn't much shorter. ;)
Regards,
Alexander
| |