dgnc_driver_pollrate_store needs to take a lock before modifying the
shared variable dgnc_poll_tick.

Signed-off-by: Salah Triki <salah.tr...@acm.org>
---
 drivers/staging/dgnc/dgnc_sysfs.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/dgnc/dgnc_sysfs.c 
b/drivers/staging/dgnc/dgnc_sysfs.c
index 44db870..204ae05 100644
--- a/drivers/staging/dgnc/dgnc_sysfs.c
+++ b/drivers/staging/dgnc/dgnc_sysfs.c
@@ -57,10 +57,20 @@ static ssize_t dgnc_driver_pollrate_store(struct 
device_driver *ddp,
                                          const char *buf, size_t count)
 {
        int ret;
+       int tick;
+       static DEFINE_MUTEX(mut);
 
-       ret = sscanf(buf, "%d\n", &dgnc_poll_tick);
+       ret = sscanf(buf, "%d\n", &tick);
        if (ret != 1)
                return -EINVAL;
+
+       ret = mutex_lock_interruptible(&mut);
+       if (ret)
+               return -ERESTARTSYS;
+
+       dgnc_poll_tick = tick;
+
+       mutex_unlock(&mut);
        return count;
 }
 static DRIVER_ATTR(pollrate, (S_IRUSR | S_IWUSR), dgnc_driver_pollrate_show,
-- 
1.9.1

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