USB: Remove BKL from poll()

Replace BKL with usbfs_mutex to protect a global counter
and a per file data structure

Signed-off-by: Oliver Neukum <oliver@neukum.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 9 insertions, 19 deletions

diff --git a/drivers/usb/core/devices.c b/drivers/usb/core/devices.c
index 355dffcc23b..175529fd02f 100644
--- a/drivers/usb/core/devices.c
+++ b/drivers/usb/core/devices.c
@@ -118,6 +118,7 @@ static const char *format_endpt =
  */
 
 static DECLARE_WAIT_QUEUE_HEAD(deviceconndiscwq);
+/* guarded by usbfs_mutex */
 static unsigned int conndiscevcnt;
 
 /* this struct stores the poll state for <mountpoint>/devices pollers */
@@ -156,7 +157,9 @@ static const struct class_info clas_info[] =
 
 void usbfs_conn_disc_event(void)
 {
+        mutex_lock(&usbfs_mutex);
         conndiscevcnt++;
+        mutex_unlock(&usbfs_mutex);
         wake_up(&deviceconndiscwq);
 }
 
@@ -629,42 +632,29 @@ static ssize_t usb_device_read(struct file *file, char __user *buf,
 static unsigned int usb_device_poll(struct file *file,
                                     struct poll_table_struct *wait)
 {
-        struct usb_device_status *st = file->private_data;
+        struct usb_device_status *st;
         unsigned int mask = 0;
 
-        lock_kernel();
+        mutex_lock(&usbfs_mutex);
+        st = file->private_data;
         if (!st) {
                 st = kmalloc(sizeof(struct usb_device_status), GFP_KERNEL);
-
-                /* we may have dropped BKL -
-                 * need to check for having lost the race */
-                if (file->private_data) {
-                        kfree(st);
-                        st = file->private_data;
-                        goto lost_race;
-                }
-                /* we haven't lost - check for allocation failure now */
                 if (!st) {
-                        unlock_kernel();
+                        mutex_unlock(&usbfs_mutex);
                         return POLLIN;
                 }
 
-                /*
-                 * need to prevent the module from being unloaded, since
-                 * proc_unregister does not call the release method and
-                 * we would have a memory leak
-                 */
                 st->lastev = conndiscevcnt;
                 file->private_data = st;
                 mask = POLLIN;
         }
-lost_race:
+
         if (file->f_mode & FMODE_READ)
                 poll_wait(file, &deviceconndiscwq, wait);
         if (st->lastev != conndiscevcnt)
                 mask |= POLLIN;
         st->lastev = conndiscevcnt;
-        unlock_kernel();
+        mutex_unlock(&usbfs_mutex);
         return mask;
 }