linux-kernel - Re: [Bisected] [Bug #13821] Replugging USB serial converter uses new device node

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Message-ID: <Pine.LNX.4.44L0.0907271217441.5217-100000@iolanthe.rowland.org>
Date:	Mon, 27 Jul 2009 12:18:36 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Ferenc Wagner <wferi@...f.hu>
cc:	"Carlos R. Mafra" <crmafra2@...il.com>, Greg KH <greg@...ah.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Kernel Testers List <kernel-testers@...r.kernel.org>,
	USB list <linux-usb@...r.kernel.org>,
	Kay Sievers <kay.sievers@...y.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: [Bisected] [Bug #13821] Replugging USB serial converter uses
 new device node

On Mon, 27 Jul 2009, Ferenc Wagner wrote:

> > Are you certain this really is a regression?  Under 2.6.30 and 2.6.27
> > the same thing happened if I unplugged a USB serial device while it was
> > in use.
> 
> My original report is about unplugging the USB servial device *after*
> using it.
> 
> > Can you check whether the device is still being used when you unplug 
> > it?  For instance, is there still a pppd process trying to communicate 
> > with the device?
> 
> I checked and rechecked that the pppd process is already dead by the
> time I unplug the device.  However, the minor number did not increase
> if I unplugged the device without using it beforehand, as expected.
> 
> > In short, it seems likely that this is not new behavior but rather the 
> > way usb-serial has worked all along.
> 
> I didn't experience this problem with 2.6.30: my ppp script was
> hardwired to use ttyUSB0 and it always worked.  Now with 2.6.31-rc3 it
> does not, as the device node keeps changing.
> 
> I'll test this with opening ttyUSB directly from the shell, instead of
> via pppd, and report back whether it makes a difference.

Another thing to check is whether this patch (not yet merged) fixes it:

	http://marc.info/?l=linux-usb&m=124825571403844&w=2

Alan Stern

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