[media] dvb_frontend: fix ioctls failing if frontend open/closed too fast

That likely fixes this MythTV ticket:
	http://code.mythtv.org/trac/ticket/10830
(which btw affects all usb tuners I tested as well, pctv452e,
dib0700, af9015)  pctv452e is still possibly broken with MythTV
even after this fix; it does work with VDR here tho despite I2C
errors.
Reduced testcase:
	http://people.freebsd.org/~nox/tmp/ioctltst.c
Thanx to devinheitmueller and crope from #linuxtv for helping with
this fix! :)

Signed-off-by: Juergen Lock <nox@jelal.kn-bremen.de>
Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

diff --git a/drivers/media/dvb-core/dvb_frontend.c b/drivers/media/dvb-core/dvb_frontend.c
index 49d95040096a42589627d7e3446df5f470c2f919..9b4a47c104a109fb2deca031537ff59155d28b1d 100644 (file)
--- a/drivers/media/dvb-core/dvb_frontend.c
+++ b/drivers/media/dvb-core/dvb_frontend.c
@@ -603,6 +603,7 @@ static int dvb_frontend_thread(void *data)
        enum dvbfe_algo algo;
 
        bool re_tune = false;
+       bool semheld = false;
 
        dev_dbg(fe->dvb->device, "%s:\n", __func__);
 
@@ -626,6 +627,8 @@ restart:
 
                if (kthread_should_stop() || dvb_frontend_is_exiting(fe)) {
                        /* got signal or quitting */
+                       if (!down_interruptible(&fepriv->sem))
+                               semheld = true;
                        fepriv->exit = DVB_FE_NORMAL_EXIT;
                        break;
                }
@@ -741,6 +744,8 @@ restart:
                fepriv->exit = DVB_FE_NO_EXIT;
        mb();
 
+       if (semheld)
+               up(&fepriv->sem);
        dvb_frontend_wakeup(fe);
        return 0;
 }
@@ -1823,16 +1828,20 @@ static int dvb_frontend_ioctl(struct file *file,
        int err = -ENOTTY;
 
        dev_dbg(fe->dvb->device, "%s: (%d)\n", __func__, _IOC_NR(cmd));
-       if (fepriv->exit != DVB_FE_NO_EXIT)
+       if (down_interruptible(&fepriv->sem))
+               return -ERESTARTSYS;
+
+       if (fepriv->exit != DVB_FE_NO_EXIT) {
+               up(&fepriv->sem);
                return -ENODEV;
+       }
 
        if ((file->f_flags & O_ACCMODE) == O_RDONLY &&
            (_IOC_DIR(cmd) != _IOC_READ || cmd == FE_GET_EVENT ||
-            cmd == FE_DISEQC_RECV_SLAVE_REPLY))
+            cmd == FE_DISEQC_RECV_SLAVE_REPLY)) {
+               up(&fepriv->sem);
                return -EPERM;
-
-       if (down_interruptible (&fepriv->sem))
-               return -ERESTARTSYS;
+       }
 
        if ((cmd == FE_SET_PROPERTY) || (cmd == FE_GET_PROPERTY))
                err = dvb_frontend_ioctl_properties(file, cmd, parg);