Hi Matti, On 2/19/19 6:30 AM, Matti Hämäläinen wrote: > > Hello! > > Last week while testing some webcams that use gspca-based v4l2 drivers, I > noticed that the driver was spewing some errors in klog whenever the > program using them issued VIDIOC_STREAMOFF ioctl. This seems to be a > regression caused by commit 1f5965c4dfd7665f2914a1f1095dcc6020656b04 > "media: gspca: convert to vb2" in the mainline kernel. > > The errors were as follows (with gspca_main debug=3): > [ 2497.147902] gspca_zc3xx 3-9.3.2:1.0: isoc 32 pkts size 768 = bsize:24576 > [ 2498.194657] gspca_zc3xx 3-9.3.2:1.0: probe 2wr ov vga 0x0000 > [ 2499.602538] gspca_zc3xx 3-9.3.2:1.0: found int in endpoint: 0x82, buffer_len=8, interval=10 > [ 2501.785244] gspca_zc3xx 3-9.3.2:1.0: kill transfer > [ 2501.787218] gspca_zc3xx 3-9.3.2:1.0: urb status: -2 > [ 2501.787223] gspca_main: usb_submit_urb() ret -1 > [ 2501.789217] gspca_zc3xx 3-9.3.2:1.0: urb status: -2 > [ 2501.789222] gspca_main: usb_submit_urb() ret -1 > [ 2501.791218] gspca_zc3xx 3-9.3.2:1.0: urb status: -2 > [ 2501.791223] gspca_main: usb_submit_urb() ret -1 > [ 2501.791226] gspca_zc3xx 3-9.3.2:1.0: releasing urbs > [ 2501.795919] gspca_zc3xx 3-9.3.2:1.0: found int in endpoint: 0x82, buffer_len=8, interval=10 > [ 2501.870710] gspca_zc3xx 3-9.3.2:1.0: stream off OK > > Additionally I noticed that on another PC I could trigger a complete > hard system lockup simply by unplugging the USB camera when a video > capture was ongoing AND while running under Xorg. (For some reason > without Xorg there was no hang.) > > Also, on the same system another gspca camera (again with this commit) > results in following errors on "clean" disconnect, e.g. plug on/off and no > capture running: > > [ 8492.613643] STV06xx 4-2:1.0: URB error -84, resubmitting > [ 8492.661638] STV06xx 4-2:1.0: URB error -84, resubmitting > [ 8492.709638] STV06xx 4-2:1.0: URB error -84, resubmitting > [ 8492.755542] usb 4-2: USB disconnect, device number 3 > > > While I am no kernel dev, I believe that the changes to the mutex locking > in the aforementioned commit are probably causing some race conditions. > > What I think is happening in the first case (urb status errors) is that > when userspace program does ioctl(fd, VIDIOC_STREAMOFF, V4L2_BUF_TYPE_VIDEO_CAPTURE), > the kernel goes to gspca_stream_off() and through that to destroy_urbs(). > > Meanwhile fill_frame() can get called from isoc_irq(), which then results > in the failures that spew "urb status: -2" to klog, goto resubmit -> > "usb_submit_urb() ret -1" > > Sorry if I've forgotten to provide some relevant information, > feel free to ask if something is required. > Which kernel version are you using? I got other, similar reports as well and I plan to look at it next week. Regards, Hans
