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    Subject[PATCH 15/18] dvb/bt8xx: kill the big kernel lock
    Date
    The bt8xx driver only uses the big kernel lock in its dst_ca_ioctl
    function and never to serialize against other code, so we can
    trivially replace it with a private mutex.

    Signed-off-by: Arnd Bergmann <arnd@arndb.de>
    Cc: linux-media@vger.kernel.org
    Cc: Mauro Carvalho Chehab <mchehab@infradead.org>
    ---
    drivers/media/dvb/bt8xx/dst_ca.c | 7 ++++---
    1 files changed, 4 insertions(+), 3 deletions(-)

    diff --git a/drivers/media/dvb/bt8xx/dst_ca.c b/drivers/media/dvb/bt8xx/dst_ca.c
    index cf87051..d75788b 100644
    --- a/drivers/media/dvb/bt8xx/dst_ca.c
    +++ b/drivers/media/dvb/bt8xx/dst_ca.c
    @@ -22,7 +22,7 @@
    #include <linux/module.h>
    #include <linux/slab.h>
    #include <linux/init.h>
    -#include <linux/smp_lock.h>
    +#include <linux/mutex.h>
    #include <linux/string.h>
    #include <linux/dvb/ca.h>
    #include "dvbdev.h"
    @@ -52,6 +52,7 @@
    } while(0)


    +static DEFINE_MUTEX(dst_ca_mutex);
    static unsigned int verbose = 5;
    module_param(verbose, int, 0644);
    MODULE_PARM_DESC(verbose, "verbose startup messages, default is 1 (yes)");
    @@ -564,7 +565,7 @@ static long dst_ca_ioctl(struct file *file, unsigned int cmd, unsigned long ioct
    void __user *arg = (void __user *)ioctl_arg;
    int result = 0;

    - lock_kernel();
    + mutex_lock(&dst_ca_mutex);
    dvbdev = file->private_data;
    state = (struct dst_state *)dvbdev->priv;
    p_ca_message = kmalloc(sizeof (struct ca_msg), GFP_KERNEL);
    @@ -652,7 +653,7 @@ static long dst_ca_ioctl(struct file *file, unsigned int cmd, unsigned long ioct
    kfree (p_ca_slot_info);
    kfree (p_ca_caps);

    - unlock_kernel();
    + mutex_unlock(&dst_ca_mutex);
    return result;
    }

    --
    1.7.1


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