On Tue, Apr 08, 2014 at 12:22:22PM +0200, Oliver Neukum wrote: > On Tue, 2014-04-08 at 09:33 +0200, Johan Hovold wrote: > > On Tue, Apr 08, 2014 at 11:05:20AM +0800, Xiao Jin wrote: > > > We find two problems on acm tty write delayed mechanism. > > > > Then you should split this into two patches. > > > > > (1) When acm resume, the delayed wb will be started. But now > > > only one write can be saved during acm suspend. More acm write > > > may be abandoned. > > > > Why not simply return 0 in write and use the tty buffering rather than > > implement another buffer in cdc_acm? > > Yes. We need a single buffer because the tty layer is not happy > when you accept no data. But we should be able to refuse subsequent > writes. Could you test this patch? > > Regards > Oliver > > From 1d44c1f2a10b5617824a37c8ec51f5547e482259 Mon Sep 17 00:00:00 2001 > From: Oliver Neukum <oneukum@xxxxxxx> > Date: Tue, 8 Apr 2014 12:17:39 +0200 > Subject: [PATCH] cdc-acm: fix consecutive writes while device is suspended > > CDC-ACM needs to handle one attempt to write to a suspended > device because we told the tty layer that there is room. > A second attempt may and must fail or we drop data. > > Signed-off-by: Oliver Neukum <oneukum@xxxxxxx> > CC: stable@xxxxxxxxxxxxxxx > --- > drivers/usb/class/cdc-acm.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c > index 900f7ff..7ad3105 100644 > --- a/drivers/usb/class/cdc-acm.c > +++ b/drivers/usb/class/cdc-acm.c > @@ -646,10 +646,12 @@ static int acm_tty_write(struct tty_struct *tty, > > usb_autopm_get_interface_async(acm->control); > if (acm->susp_count) { > - if (!acm->delayed_wb) > + if (!acm->delayed_wb) { > acm->delayed_wb = wb; > - else > + } else { > usb_autopm_put_interface_async(acm->control); > + count = 0; You would still leak write urbs here, unless you set wb.use = 0. > + } > spin_unlock_irqrestore(&acm->write_lock, flags); > return count; /* A white lie */ > } -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html