From: Oliver Neukum <oliver@neukum.org>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>,
linux-next@vger.kernel.org, linux-kernel@vger.kernel.org,
Greg KH <greg@kroah.com>
Subject: Re: linux-next: manual merge of the ttydev tree with the usb.current tree
Date: Tue, 28 Jul 2009 14:10:40 +0200 [thread overview]
Message-ID: <200907281410.41449.oliver@neukum.org> (raw)
In-Reply-To: <20090728112608.09a494e0@lxorguk.ukuu.org.uk>
Am Dienstag, 28. Juli 2009 12:26:08 schrieb Alan Cox:
> On Tue, 28 Jul 2009 14:01:10 +1000
>
> Stephen Rothwell <sfr@canb.auug.org.au> wrote:
> > Hi Alan,
> >
> > Today's linux-next merge of the ttydev tree got a conflict in
> > drivers/usb/serial/usb-serial.c between commit
> > a00b8d98aca97bfb6fa983f41dae25b424058592 ("USB: fix usage count in usb
> > serial generic open regarding autoresume") from the usb.current tree
>
> That looks wrong. The extra fiddling with port.count looks both unsafe
> and incorrect. I've never seen the "autoresume" patch referred to so I've
> no idea what it is trying to do
The problem is subdrivers looking at port->count to determine
whether URBs have to be resubmitted. That must happen once.
Therefore if serial_open() needs to do it itself it must make sure
resume() runs without port->count already incremented.
As serial_open() takes the lock, resume() must not do so.
If however, remote wakeup is used a lock must be taken
to look at port->count reliably. As this is impossible, the patch
implementing use of remote wakeup for the option driver
implements a private flag for opened ports.
This code from option_resume():
for (i = 0; i < serial->num_ports; i++) {
/* walk all ports */
port = serial->port[i];
portdata = usb_get_serial_port_data(port);
mutex_lock(&port->mutex);
/* skip closed ports */
if (!port->port.count) {
mutex_unlock(&port->mutex);
continue;
}
for (j = 0; j < N_IN_URB; j++) {
urb = portdata->in_urbs[j];
err = usb_submit_urb(urb, GFP_NOIO);
if (err < 0) {
mutex_unlock(&port->mutex);
err("%s: Error %d for bulk URB %d",
__func__, err, i);
return err;
}
}
mutex_unlock(&port->mutex);
must not take the port->mutex.
Unfortunately I have no access to my trees today and yesterday.
Regards
Oliver
next prev parent reply other threads:[~2009-07-28 12:10 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-07-28 4:01 linux-next: manual merge of the ttydev tree with the usb.current tree Stephen Rothwell
2009-07-28 10:26 ` Alan Cox
2009-07-28 12:10 ` Oliver Neukum [this message]
2009-07-28 12:29 ` Alan Cox
2009-07-28 12:35 ` Stephen Rothwell
2009-07-28 13:17 ` Alan Cox
2009-07-28 16:32 ` Greg KH
2009-07-28 16:34 ` Greg KH
2009-07-28 19:21 ` Oliver Neukum
2009-07-28 19:24 ` Alan Cox
-- strict thread matches above, loose matches on Subject: below --
2009-07-09 3:04 Stephen Rothwell
2009-07-09 23:19 ` Greg KH
2009-07-10 0:06 ` Stephen Rothwell
2009-07-10 0:13 ` Greg KH
2009-04-23 4:49 Stephen Rothwell
2009-04-23 4:34 Stephen Rothwell
2009-04-23 4:30 Stephen Rothwell
2009-04-22 3:38 Stephen Rothwell
2009-04-22 15:50 ` Alan Stern
2009-04-22 16:30 ` Alan Cox
2009-04-22 16:38 ` Greg KH
2009-04-28 4:42 ` Stephen Rothwell
2009-04-28 4:58 ` Greg KH
2009-04-28 6:45 ` Stephen Rothwell
2009-03-12 4:04 Stephen Rothwell
2009-03-12 9:44 ` Alan Cox
2009-03-12 11:02 ` Stephen Rothwell
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