On Monday 02 February 2009, Alan Stern wrote: > On Mon, 2 Feb 2009 kilgota@xxxxxxxxxxxxxxxxxxxxxx wrote: > > The attached file is an extract from dmesg from the Pentium4 Dual Core > > machine. One can see that the camera has been attached, and then an svv > > session has been run. The kernel is the "stock" Slackware 2.6.27.7 kernel > > (*). We have a situation, again, in which svv (**) can not be exited. We > > have an oops in the log, and we have a filesystem check on reboot, which > > is going on as I write this. > > Well, the problem is clear enough, and it is in the gspca.c module, not > your sq905-3 driver. I'm not sure what the best way is to fix it, so > I'm CC'ing the people responsible for the gspca driver. > Thanks for confirming that Alan. I'd been looking at this too and suspected this was the case but as it wouldn't fail on my uniprocessor machine I couldn't prove it. (Theodore, if you can generate the log we discussed of this failing it might still be helpful in tracking down the underlying problem.) > To summarize: Unplugging the camera while it is in use by a program > causes an oops (particularly on an SMP machine). > > The problem is that gspca_stream_off() calls destroy_urbs(), which in > turn calls usb_buffer_free() -- but this happens too late, after > gspca_disconnect() has returned. By that time gspca_dev->dev is a > stale pointer, so it shouldn't be passed to usb_buffer_free(). > By my reading it should be OK for gspca_disconnect to have returned as long as video_unregister_device waits for the last close to complete before calling gspca_release. I know that there were some patches a while back that attempted to ensure that was the case so I suspect there is still a hole there. > What should happen is that as part of disconnect processing, the > existing stream(s) should be put in an error state and destroy_urbs() > should be called immediately. Then when gspca_stream_off() calls > destroy_urbs() again there would be no more work left to do. > > Alan Stern > Adam Baker -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
