Add explicit lock_kernel() calls to hwicap_open() even though the existing
locking looks adequate.
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
 #include <linux/poll.h>
 #include <linux/proc_fs.h>
 #include <linux/mutex.h>
+#include <linux/smp_lock.h>
 #include <linux/sysctl.h>
 #include <linux/version.h>
 #include <linux/fs.h>
        struct hwicap_drvdata *drvdata;
        int status;
 
+       lock_kernel();
        drvdata = container_of(inode->i_cdev, struct hwicap_drvdata, cdev);
 
        status = mutex_lock_interruptible(&drvdata->sem);
        if (status)
-               return status;
+               goto out;
 
        if (drvdata->is_open) {
                status = -EBUSY;
 
  error:
        mutex_unlock(&drvdata->sem);
+ out:
+       unlock_kernel();
        return status;
 }