On Wed, May 23, 2018 at 02:08:27PM +0200, Oliver Neukum wrote:
> 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.
Processes can share file descriptors as well, no need to mess with a
thread :)
good catch.
greg k-h
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