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

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Message-ID: <20090727164857.GA8908@Pilar.aei.mpg.de>
Date:	Mon, 27 Jul 2009 18:48:57 +0200
From:	"Carlos R. Mafra" <crmafra2@...il.com>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Ferenc Wagner <wferi@...f.hu>, 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'09 at 12:18:36 -0400, Alan Stern wrote:
> 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

No, unfortunately it does not fix it. I've just tested it.
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