TTY: tty_buffer, warn on leaks

When we leak some tty buffer, warn about that. For that we need to
account the memory used also in the tty_buffer_free_all function. On
other locations, the accounting is handled correctly.

Note that we do not account the free list, as that was accounted in
tty_buffer_free before put on the free list.

I have been using this patch for ages, so let's see if anybody else
encounters any issues.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 6 insertions, 1 deletions

diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c
index c996b6859c5e..76151c002858 100644
--- a/drivers/tty/tty_buffer.c
+++ b/drivers/tty/tty_buffer.c
@@ -118,9 +118,12 @@ void tty_buffer_free_all(struct tty_port *port)
         struct tty_bufhead *buf = &port->buf;
         struct tty_buffer *p, *next;
         struct llist_node *llist;
+        unsigned int freed = 0;
+        int still_used;
 
         while ((p = buf->head) != NULL) {
                 buf->head = p->next;
+                freed += p->size;
                 if (p->size > 0)
                         kfree(p);
         }
@@ -132,7 +135,9 @@ void tty_buffer_free_all(struct tty_port *port)
         buf->head = &buf->sentinel;
         buf->tail = &buf->sentinel;
 
-        atomic_set(&buf->mem_used, 0);
+        still_used = atomic_xchg(&buf->mem_used, 0);
+        WARN(still_used != freed, "we still have not freed %d bytes!",
+                        still_used - freed);
 }
 
 /**