Zitat von Oliver Neukum <oneukum@xxxxxxxx>:
Am Donnerstag, den 17.05.2018, 19:03 +0200 schrieb Guido Kiener:+static int usbtmc488_ioctl_wait_srq(struct usbtmc_file_data *file_data, + unsigned int __user *arg) +{ + struct usbtmc_device_data *data = file_data->data; + struct device *dev = &data->intf->dev; + int rv; + unsigned int timeout; + unsigned long expire; + + if (!data->iin_ep_present) { + dev_dbg(dev, "no interrupt endpoint present\n"); + return -EFAULT; + } + + if (get_user(timeout, arg)) + return -EFAULT; + + expire = msecs_to_jiffies(timeout); + + mutex_unlock(&data->io_mutex);There is such a thing as threads sharing file descriptors. That leads to the question what happens to the mutex if this ioctl() is called multiple times. Regards Oliver
Multiple threads can wait with the same or different file descriptors. When an SRQ interrupt occurs, all threads and file descriptors are informed concurrently with wake_up_interruptible_all(&data->waitq); The "_all" is already fixed in 02/12. Regards, Guido -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
