Hi everyone, In the process of extending the libsuinput library (https://github.com/tuomasjjrasanen/python-uinput/tree/master/libsuinput/src) to support force feedback, I encountered some bugs in the kernel. For some bugs, I'm not sure for the right fix, so it's safer to first present the problem and ask for feedback. For clarity, I divided the bugs between different mail subjects. This subject handles about a deadlock encountered when userspace issues a UI_DEV_DESTROY ioctl on a uinput device, while a non-zero number of ff_effects is still active (i.e. the application that issued the ioctl has not yet erased all uploaded effects). The mutex causing the deadlock is "(struct uinput_device).mutex". The chain of the deadlock is as follows: - uinput.c::uinput_ioctl_handler() LOCKS using mutex_lock_interruptible() - uinput.c::uinput_ioctl_handler() calls uinput.c::uinput_destroy_device() - uinput.c::uinput_destroy_device() calls input.c::input_unregister_device() - input.c::input_unregister_device() calls input.c::__input_unregister_device() - input.c::__input_unregister_device() calls handle->handler->disconnect() - evdev.c::evdev_disconnect calls evdev.c::evdev_cleanup() - evdev.c::evdev_cleanup() calls input.c::input_flush_device() - input.c::input_flush_device() calls dev->flush() - ff-core.c::flush_effects() calls ff-core.c::erase_effect() - ff-core.c::erase_effect() calls ff->erase() - uinput.c::uinput_dev_erase_effect() calls uinput.c::uinput_request_submit() - uinput.c::uinput_request_submit() calls uinput.c::uinput_request_send() - uinput.c::uinput_request_send() LOCKS using mutex_lock_interruptible() Hints for solving this problem are much appreciated. Maybe by setting a flag when UI_DEV_DESTROY ioctl is issued, and avoiding to acquire the mutex in uinput_request_send() when this flag is found to be set? Thanks, Elias -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
