1 files changed, 4 insertions, 5 deletions

diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index 20104443081a..d50a99f70aee 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -158,16 +158,12 @@ static int acm_wb_is_avail(struct acm *acm)
 }
 
 /*
- * Finish write.
+ * Finish write. Caller must hold acm->write_lock
  */
 static void acm_write_done(struct acm *acm, struct acm_wb *wb)
 {
-        unsigned long flags;
-
-        spin_lock_irqsave(&acm->write_lock, flags);
         wb->use = 0;
         acm->transmitting--;
-        spin_unlock_irqrestore(&acm->write_lock, flags);
 }
 
 /*
@@ -482,6 +478,7 @@ static void acm_write_bulk(struct urb *urb)
 {
         struct acm_wb *wb = urb->context;
         struct acm *acm = wb->instance;
+        unsigned long flags;
 
         if (verbose || urb->status
                         || (urb->actual_length != urb->transfer_buffer_length))
@@ -490,7 +487,9 @@ static void acm_write_bulk(struct urb *urb)
                         urb->transfer_buffer_length,
                         urb->status);
 
+        spin_lock_irqsave(&acm->write_lock, flags);
         acm_write_done(acm, wb);
+        spin_unlock_irqrestore(&acm->write_lock, flags);
         if (ACM_READY(acm))
                 schedule_work(&acm->work);
         else