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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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