Here's a question about how to use a kthread. The usb-storage driver creates a new thread to do LUN scanning whenever a newly-hotplugged device is detected. This scanning involves waiting for several seconds and then carrying out a potentially long-lasting series of I/O operations. So we don't want to use schedule_work(); instead we create a new thread to do it.
Once the scanning thread's work is done, there's no reason for it to hang around. The driver's probe() method has long since exited, leaving nobody to reap the thread. Of course it could always just exit normally, without checking kthread_should_stop(), but... If the device is unplugged during that initial several-second-long delay period, we need to stop the scanning thread immediately. The obvious answer is to use kthread_stop(), but that's not consistent with the thread's normal behavior of exiting without waiting for kthread_should_stop(). Another problem arises as well. If the driver's remove() method doesn't call kthread_stop() then it doesn't have any straightforward way to wait for the thread to exit. This leads to the possibility that the driver's module could be unloaded while the scanning thread is still running. Would the best approach be to set up a special-purpose struct completion? Then the thread could call complete_and_exit() and the remove() method could wait for it safely. Alan Stern - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
