From 6594690b39f9f9fcadafb1caf019bfd7a326e2e5 Mon Sep 17 00:00:00 2001 From: Darron Broad Date: Wed, 15 Oct 2008 13:37:59 -0300 Subject: [PATCH] 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 Signed-off-by: Steven Toth Signed-off-by: Mauro Carvalho Chehab --- drivers/media/dvb/dvb-core/dvb_frontend.c | 57 +++++++++++++---------- 1 file changed, 32 insertions(+), 25 deletions(-) diff --git a/drivers/media/dvb/dvb-core/dvb_frontend.c b/drivers/media/dvb/dvb-core/dvb_frontend.c index 62696f865576..6c9b9be9e286 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; - } - } - mutex_lock (&adapter->mfe_lock); - mfedev = adapter->mfe_dvbdev; - mfe = mfedev->priv; - mfepriv = mfe->frontend_priv; - if (mfedev->users != -1 || mfepriv->thread != NULL) { - ret = -EBUSY; - goto err0; + + 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; } } - adapter->mfe_dvbdev = dvbdev; + + 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) { + mutex_unlock (&adapter->mfe_lock); + return -EBUSY; + } + adapter->mfe_dvbdev = dvbdev; + } } }