example.c ends in a segfault about libuvc

[coreylowman]

I am currently running it on a beaglebone black, and sometimes it runs fine, but sometimes it does segfault. I ran gdb on it and it seems like its crashing in a call libusb. It crashes in uvc_stop_streaming call.

[ovchinnikov-v-a]

It seems I've had the same trouble - my app using libuvc crashes when trying to close device with uvc_close() after starting a stream with uvc_stream_start().

The actual problem was in function called uvc_stream_stop - there is erroneous usage of libusb_cancel_transfer return value:

int res = libusb_cancel_transfer(strmh->transfers[i]); if(res < 0) { free(strmh->transfers[i]->buffer); libusb_free_transfer(strmh->transfers[i]); strmh->transfers[i] = NULL; }

It is not valid to free transfer immediately after libusb_cancel_transfer returned negative result cause this transfer may still be used in uvc_iso_callback function.

So I commented out transfer freeing code in uvc_stream_stop and add transfer deletion to uvc_iso_callback for LIBUSB_TRANSFER_COMPLETED, LIBUSB_TRANSFER_TIMED_OUT, LIBUSB_TRANSFER_STALL and LIBUSB_TRANSFER_OVERFLOW cases.
Of course transfer deletion in uvc_iso_callback for these cases should happen only when strmh->running == 0.

I'm not sure if this quick and dirty solution is the best one, but it works for me - no more crashes when calling uvc_close(). My current version of stream.c is attached.
stream.zip