tty: Ensure single-threaded flip buffer consumer with mutex

The buffer work may race with parallel tty_buffer_flush. Use a
mutex to guarantee exclusive modify access to the head flip
buffer.

Remove the unneeded spin lock.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/include/linux/tty.h b/include/linux/tty.h
index 7c124541f011..1c8fef0e3ff6 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -66,7 +66,7 @@ static inline char *flag_buf_ptr(struct tty_buffer *b, int ofs)
 
 struct tty_bufhead {
         struct work_struct work;
-        spinlock_t lock;
+        struct mutex flush_mutex;
         struct tty_buffer sentinel;
         struct tty_buffer *head;        /* Queue head */
         struct tty_buffer *tail;        /* Active buffer */