Hi,

Lu Baolu <baolu.lu@linux.intel.com> writes:
> In sg_timeout(), req->status is set to "-ETIMEDOUT" before calling
> into usb_sg_cancel(). usb_sg_cancel() will do nothing and return
> directly if req->status has been set to a non-zero value. This will
> cause driver hang as soon as transfer time out is triggered.
>
> In my test case, below system log shows when port reset happens after
> urb being submitted.
>
> [55099.746213] usb 2-3: USB disconnect, device number 2
> [55321.955451] INFO: task kworker/6:0:59 blocked for more than 120 seconds.
> [55321.955463]       Not tainted 4.7.0-rc6+ #19
> [55321.955466] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> [55321.955472] kworker/6:0     D ffff88045ad3bbf8     0    59      2 0x00000000
> [55321.955489] Workqueue: usb_hub_wq hub_event
> [55321.955493]  ffff88045ad3bbf8 ffff880400000030 ffff88045ad30f40 ffff88045ad3bbd0
> [55321.955499]  ffff88045ad3c000 ffff8804590920fc ffff88045ad30f40 00000000ffffffff
> [55321.955505]  ffff880459092100 ffff88045ad3bc10 ffffffff817b5925 ffff8804590920f8
> [55321.955511] Call Trace:
> [55321.955521]  [<ffffffff817b5925>] schedule+0x35/0x80
> [55321.955527]  [<ffffffff817b5c1e>] schedule_preempt_disabled+0xe/0x10
> [55321.955533]  [<ffffffff817b7505>] __mutex_lock_slowpath+0x95/0x110
> [55321.955538]  [<ffffffff817b759f>] mutex_lock+0x1f/0x2f
> [55321.955544]  [<ffffffff815b28a3>] usb_disconnect+0x53/0x270
> [55321.955550]  [<ffffffff815b4521>] hub_port_connect+0x71/0x900
> [55321.955556]  [<ffffffff815b08be>] ? hub_port_reset+0x3de/0x630
> [55321.955562]  [<ffffffff815b53ee>] hub_event+0x63e/0xb20
> [55321.955569]  [<ffffffff810ae675>] ? put_prev_entity+0x35/0x730
> [55321.955577]  [<ffffffff810921f3>] process_one_work+0x153/0x3f0
> [55321.955583]  [<ffffffff810929ab>] worker_thread+0x12b/0x4b0
> [55321.955590]  [<ffffffff81092880>] ? rescuer_thread+0x340/0x340
> [55321.955595]  [<ffffffff810981c9>] kthread+0xc9/0xe0
> [55321.955601]  [<ffffffff817b961f>] ret_from_fork+0x1f/0x40
> [55321.955606]  [<ffffffff81098100>] ? kthread_park+0x60/0x60
> [55321.955638] INFO: task testusb:3011 blocked for more than 120 seconds.
> [55321.955643]       Not tainted 4.7.0-rc6+ #19
> [55321.955647] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> [55321.955651] testusb         D ffff880449a079f8     0  3011   2367 0x00000000
> [55321.955657]  ffff880449a079f8 0000000000000002 ffff88045754cc40 ffffffff815b91b9
> [55321.955663]  ffff880449a08000 7fffffffffffffff ffff880449a07cb0 ffff88045754cc40
> [55321.955668]  0000000000000000 ffff880449a07a10 ffffffff817b5925 ffff880449a07cb8
> [55321.955673] Call Trace:
> [55321.955680]  [<ffffffff815b91b9>] ? usb_hcd_submit_urb+0xa9/0xba0
> [55321.955685]  [<ffffffff817b5925>] schedule+0x35/0x80
> [55321.955691]  [<ffffffff817b8661>] schedule_timeout+0x231/0x2d0
> [55321.955698]  [<ffffffff8117a592>] ? __alloc_pages_nodemask+0x112/0x2b0
> [55321.955703]  [<ffffffff817b62e4>] wait_for_completion+0xa4/0x110
> [55321.955709]  [<ffffffff810a2cb0>] ? wake_up_q+0x80/0x80
> [55321.955713]  [<ffffffff815bcf78>] usb_sg_wait+0x138/0x190
> [55321.955722]  [<ffffffffc01b6fdf>] perform_sglist+0xef/0x180 [usbtest]
> [55321.955728]  [<ffffffffc01b6020>] ? usbtest_resume+0x10/0x10 [usbtest]
> [55321.955734]  [<ffffffffc01b9648>] usbtest_do_ioctl+0x898/0x1520 [usbtest]
> [55321.955740]  [<ffffffff815ba2a5>] ? usb_hcd_reset_endpoint+0x25/0x60
> [55321.955745]  [<ffffffff815bd4f5>] ? usb_enable_endpoint+0x85/0x90
> [55321.955751]  [<ffffffffc01ba3f3>] usbtest_ioctl+0x123/0x26e [usbtest]
> [55321.955756]  [<ffffffff81172335>] ? filemap_map_pages+0x295/0x310
> [55321.955763]  [<ffffffff815c5cc8>] ? proc_ioctl+0x48/0x210
> [55321.955769]  [<ffffffff815c5db0>] proc_ioctl+0x130/0x210
> [55321.955776]  [<ffffffff815c7d4a>] usbdev_do_ioctl+0x50a/0x1170
> [55321.955782]  [<ffffffff815c89de>] usbdev_ioctl+0xe/0x20
> [55321.955789]  [<ffffffff81207786>] do_vfs_ioctl+0x96/0x590
> [55321.955794]  [<ffffffff81203723>] ? putname+0x53/0x60
> [55321.955800]  [<ffffffff81207cf9>] SyS_ioctl+0x79/0x90
> [55321.955806]  [<ffffffff817b93f6>] entry_SYSCALL_64_fastpath+0x1e/0xa
>
> This patch fixes this driver hang. It should be back-ported to stable
> kernel with version after v3.15.
>
> Cc: stable@vger.kernel.org
> Cc: Alan Stern <stern@rowland.harvard.edu>
> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
> ---
>  drivers/usb/misc/usbtest.c | 1 -
>  1 file changed, 1 deletion(-)
>
> diff --git a/drivers/usb/misc/usbtest.c b/drivers/usb/misc/usbtest.c
> index 6b978f0..6c6586d 100644
> --- a/drivers/usb/misc/usbtest.c
> +++ b/drivers/usb/misc/usbtest.c
> @@ -585,7 +585,6 @@ static void sg_timeout(unsigned long _req)
>  {
>  	struct usb_sg_request	*req = (struct usb_sg_request *) _req;
>  
> -	req->status = -ETIMEDOUT;
>  	usb_sg_cancel(req);
>  }

IMO, req->status = -ETIMEDOUT should still be done, but perhaps after
usb_sg_cancel(). Alan?

-- 
balbi