On Mon, Jul 26, 2010 at 10:36 AM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > On Mon, 26 Jul 2010, Elly Jones wrote: > >> On Mon, Jul 26, 2010 at 12:57 AM, David Miller <davem@xxxxxxxxxxxxx> wrote: >> > From: Elly Jones <ellyjones@xxxxxxxxxx> >> > Date: Wed, 21 Jul 2010 14:51:48 -0400 >> > >> >> Subject: [patch] usbnet: fix 100% CPU use on suspended device >> >> From: Elly Jones <ellyjones@xxxxxxxxxx> >> >> >> >> This patch causes the usbnet module not to attempt to submit URBs to the device >> >> if the device is not ready to accept them. This fixes a misbehavior trigged by >> >> the Qualcomm Gobi driver (released under GPL through their Code Aurora >> >> initiative) which causes the usbnet core to consume 100% of CPU attempting and >> >> failing to submit URBs. This patch is against Linus's 2.6 repo commit >> >> a9f7f2e74ae0e6a801a2433dc8e9124d73da0cb4. >> >> Signed-off-by: Elizabeth Jones <ellyjones@xxxxxxxxxx> >> > >> > If the Qualcomm Gobi driver is the only one where this happens, maybe the >> > real problem is in that driver. >> >> The member in question (dev->udev->can_submit) is documented as 'URBs >> may be submitted'. The existing code doesn't honor that flag. It is >> somewhat puzzling that (so far) only the Gobi driver seems to use that >> flag, but I don't think the bug lies in their driver here. > > That flag is not intended for use by drivers but by the USB core. (It > gets cleared only when the device is suspended.) usbnet and Gobi > shouldn't need to look at it. Aha! >> > I'm not applying this until a USB person looks more deeply into this. >> >> Alright. Can you suggest a particular USB person to bother? >> >> >> --- >> >> diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c >> >> index 81c76ad..df7e72e 100644 >> >> --- a/drivers/net/usb/usbnet.c >> >> +++ b/drivers/net/usb/usbnet.c >> >> @@ -1172,6 +1172,7 @@ static void usbnet_bh (unsigned long param) >> >> // or are we maybe short a few urbs? >> >> } else if (netif_running (dev->net) && >> >> netif_device_present (dev->net) && >> >> + dev->udev->can_submit && >> >> !timer_pending (&dev->delay) && >> >> !test_bit (EVENT_RX_HALT, &dev->flags)) { >> >> int temp = dev->rxq.qlen; > > This isn't right. The problem should be fixed some other way. Under > what circumstances are URBs submitted incorrectly? When the device is autosuspended. What is the proper thing for a device to do here? > Alan Stern -- Elly -- 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