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Subject[PATCH 3/3] [media] cx88: use a mutex to protect cx8802_devlist
From: Ben Hutchings <ben@decadent.org.uk>
Date: Tue, 29 Mar 2011 03:25:15 +0100

Add and use a mutex to protect the cx88-mpeg device list. Previously
the BKL prevented races.

[jn: split from a larger patch, with new commit message; also protect
use in cx8802_probe]

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
---
That's the end of the series. Hopefully I haven't mangled the patches
too much --- if we're lucky they might even still work, though I
wouldn't bet on it. Bug reports and improvements welcome.
Good night,
Jonathan

drivers/media/video/cx88/cx88-mpeg.c | 20 +++++++++++++++++---
1 files changed, 17 insertions(+), 3 deletions(-)
diff --git a/drivers/media/video/cx88/cx88-mpeg.c b/drivers/media/video/cx88/cx88-mpeg.c
index 9147c16..6b58647 100644
--- a/drivers/media/video/cx88/cx88-mpeg.c
+++ b/drivers/media/video/cx88/cx88-mpeg.c
@@ -78,6 +78,7 @@ static void flush_request_modules(struct cx8802_dev *dev)


static LIST_HEAD(cx8802_devlist);
+static DEFINE_MUTEX(cx8802_mutex);
/* ------------------------------------------------------------------ */

static int cx8802_start_dma(struct cx8802_dev *dev,
@@ -689,6 +690,8 @@ int cx8802_register_driver(struct cx8802_driver *drv)
return err;
}

+ mutex_lock(&cx8802_mutex);
+
list_for_each_entry(dev, &cx8802_devlist, devlist) {
printk(KERN_INFO
"%s/2: subsystem: %04x:%04x, board: %s [card=%d]\n",
@@ -698,8 +701,10 @@ int cx8802_register_driver(struct cx8802_driver *drv)

/* Bring up a new struct for each driver instance */
driver = kzalloc(sizeof(*drv),GFP_KERNEL);
- if (driver == NULL)
- return -ENOMEM;
+ if (driver == NULL) {
+ err = -ENOMEM;
+ goto out;
+ }

/* Snapshot of the driver registration data */
drv->core = dev->core;
@@ -723,7 +728,10 @@ int cx8802_register_driver(struct cx8802_driver *drv)

}

- return i ? 0 : -ENODEV;
+ err = i ? 0 : -ENODEV;
+out:
+ mutex_unlock(&cx8802_mutex);
+ return err;
}

int cx8802_unregister_driver(struct cx8802_driver *drv)
@@ -737,6 +745,8 @@ int cx8802_unregister_driver(struct cx8802_driver *drv)
drv->type_id == CX88_MPEG_DVB ? "dvb" : "blackbird",
drv->hw_access == CX8802_DRVCTL_SHARED ? "shared" : "exclusive");

+ mutex_lock(&cx8802_mutex);
+
list_for_each_entry(dev, &cx8802_devlist, devlist) {
printk(KERN_INFO
"%s/2: subsystem: %04x:%04x, board: %s [card=%d]\n",
@@ -763,6 +773,8 @@ int cx8802_unregister_driver(struct cx8802_driver *drv)
mutex_unlock(&dev->core->lock);
}

+ mutex_unlock(&cx8802_mutex);
+
return err;
}

@@ -800,7 +812,9 @@ static int __devinit cx8802_probe(struct pci_dev *pci_dev,
goto fail_free;

INIT_LIST_HEAD(&dev->drvlist);
+ mutex_lock(&cx8802_mutex);
list_add_tail(&dev->devlist,&cx8802_devlist);
+ mutex_unlock(&cx8802_mutex);

/* now autoload cx88-dvb or cx88-blackbird */
request_modules(dev);
--
1.7.5.rc0


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