[PATCH] dvb: core: fix race condition in FE_READ_STATUS ioctl

Fix a race condition where an application which issued a FE_READ_STATUS ioctl
directly after FE_SET_FRONTEND would see an old status, i.e.  FE_READ_STATUS
would be executed before the frontend thread has even seen the tungin request
from FE_SET_FRONTEND.

Signed-off-by: Peter Beutner <p.beutner@gmx.net>
Signed-off-by: Johannes Stezenbach <js@linuxtv.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 13 insertions, 3 deletions

diff --git a/drivers/media/dvb/dvb-core/dvb_frontend.c b/drivers/media/dvb/dvb-core/dvb_frontend.c
index f11daae91cd4..e561ac1e1b16 100644
--- a/drivers/media/dvb/dvb-core/dvb_frontend.c
+++ b/drivers/media/dvb/dvb-core/dvb_frontend.c
@@ -626,11 +626,21 @@ static int dvb_frontend_ioctl(struct inode *inode, struct file *file,
                 break;
         }
 
-        case FE_READ_STATUS:
+        case FE_READ_STATUS: {
+                fe_status_t* status = parg;
+
+                /* if retune was requested but hasn't occured yet, prevent
+                 * that user get signal state from previous tuning */
+                if(fepriv->state == FESTATE_RETUNE) {
+                        err=0;
+                        *status = 0;
+                        break;
+                }
+
                 if (fe->ops->read_status)
-                        err = fe->ops->read_status(fe, (fe_status_t*) parg);
+                        err = fe->ops->read_status(fe, status);
                 break;
-
+        }
         case FE_READ_BER:
                 if (fe->ops->read_ber)
                         err = fe->ops->read_ber(fe, (__u32*) parg);