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authorDarron Broad <darron@kewl.org>2008-10-15 13:37:59 -0300
committerMauro Carvalho Chehab <mchehab@redhat.com>2008-10-17 17:28:22 -0300
commit6594690b39f9f9fcadafb1caf019bfd7a326e2e5 (patch)
treef302b75e9c1e8827ec491bdc82aebe47c0773d27
parent5c310b1360f4be8a2cf944d9d65892839ed27d00 (diff)
V4L/DVB (9264): MFE: bugfix: multi-frontend mutual exclusion parallel open
When moving from one frontend to another an application could spawn multiple threads opening the same new frontend and in some circumstances all of these could become delayed waiting for the previous frontend readers or previous frontend writer thread to complete. In this scenario the first thread will succeed on open to bring the new frontend online but any others will return EBUSY. This is a fault. If the first succeeds and all others are on the same frontend then they should succeed also. Signed-off-by: Darron Broad <darron@kewl.org> Signed-off-by: Steven Toth <stoth@linuxtv.org> Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
-rw-r--r--drivers/media/dvb/dvb-core/dvb_frontend.c49
1 files changed, 28 insertions, 21 deletions
diff --git a/drivers/media/dvb/dvb-core/dvb_frontend.c b/drivers/media/dvb/dvb-core/dvb_frontend.c
index 62696f86557..6c9b9be9e28 100644
--- a/drivers/media/dvb/dvb-core/dvb_frontend.c
+++ b/drivers/media/dvb/dvb-core/dvb_frontend.c
@@ -1710,39 +1710,46 @@ static int dvb_frontend_open(struct inode *inode, struct file *file)
struct dvb_frontend *fe = dvbdev->priv;
struct dvb_frontend_private *fepriv = fe->frontend_priv;
struct dvb_adapter *adapter = fe->dvb;
- struct dvb_device *mfedev;
- struct dvb_frontend *mfe;
- struct dvb_frontend_private *mfepriv;
- int mferetry;
int ret;
dprintk ("%s\n", __func__);
if (adapter->mfe_shared) {
mutex_lock (&adapter->mfe_lock);
- if (adapter->mfe_dvbdev != dvbdev) {
- if (adapter->mfe_dvbdev) {
- mfedev = adapter->mfe_dvbdev;
- mfe = mfedev->priv;
- mfepriv = mfe->frontend_priv;
- mutex_unlock (&adapter->mfe_lock);
- mferetry = (dvb_mfe_wait_time << 1);
- while (mferetry-- && (mfedev->users != -1 || mfepriv->thread != NULL)) {
- if(msleep_interruptible(500)) {
- if(signal_pending(current))
- return -EINTR;
- }
+
+ if (adapter->mfe_dvbdev == NULL)
+ adapter->mfe_dvbdev = dvbdev;
+
+ else if (adapter->mfe_dvbdev != dvbdev) {
+ struct dvb_device
+ *mfedev = adapter->mfe_dvbdev;
+ struct dvb_frontend
+ *mfe = mfedev->priv;
+ struct dvb_frontend_private
+ *mfepriv = mfe->frontend_priv;
+ int mferetry = (dvb_mfe_wait_time << 1);
+
+ mutex_unlock (&adapter->mfe_lock);
+ while (mferetry-- && (mfedev->users != -1 ||
+ mfepriv->thread != NULL)) {
+ if(msleep_interruptible(500)) {
+ if(signal_pending(current))
+ return -EINTR;
}
- mutex_lock (&adapter->mfe_lock);
+ }
+
+ mutex_lock (&adapter->mfe_lock);
+ if(adapter->mfe_dvbdev != dvbdev) {
mfedev = adapter->mfe_dvbdev;
mfe = mfedev->priv;
mfepriv = mfe->frontend_priv;
- if (mfedev->users != -1 || mfepriv->thread != NULL) {
- ret = -EBUSY;
- goto err0;
+ if (mfedev->users != -1 ||
+ mfepriv->thread != NULL) {
+ mutex_unlock (&adapter->mfe_lock);
+ return -EBUSY;
}
+ adapter->mfe_dvbdev = dvbdev;
}
- adapter->mfe_dvbdev = dvbdev;
}
}