Re: [PATCH 1/1] TTY: tty_buffer, warn on leaks

[Peter Hurley <peter@hurleysoftware.com>]

On 11/11/2013 03:05 PM, Jiri Slaby wrote:
> When we leak something, warn about that. For that we need to account
> the memory used also in the free_all method. It is handled elsewhere
> correctly.

Hi Jiri,

Good idea.

> Signed-off-by: Jiri Slaby <jslaby@suse.cz>
> ---
>   drivers/tty/tty_buffer.c | 10 ++++++++--
>   1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c
> index 5f08c39e76ab..20cb9492dbf8 100644
> --- a/drivers/tty/tty_buffer.c
> +++ b/drivers/tty/tty_buffer.c
> @@ -115,21 +115,27 @@ void tty_buffer_free_all(struct tty_port *port)
>   	struct tty_bufhead *buf = &port->buf;
>   	struct tty_buffer *p, *next;
>   	struct llist_node *llist;
> +	int zero = 0;
>
>   	while ((p = buf->head) != NULL) {
>   		buf->head = p->next;
> +		atomic_sub(p->size, &buf->memory_used);

buf->memory_used doesn't need to be treated atomically here,
and doing so implies that it's necessary.

Accumulating p->size in a non-atomic local is probably better.

>   		if (p->size > 0)
>   			kfree(p);
>   	}
>   	llist = llist_del_all(&buf->free);
> -	llist_for_each_entry_safe(p, next, llist, free)
> +	llist_for_each_entry_safe(p, next, llist, free) {
> +		atomic_sub(p->size, &buf->memory_used);

Same here.

>   		kfree(p);
> +	}
> +
>
>   	tty_buffer_reset(&buf->sentinel, 0);
>   	buf->head = &buf->sentinel;
>   	buf->tail = &buf->sentinel;
>
> -	atomic_set(&buf->memory_used, 0);
> +	atomic_xchg(&buf->memory_used, zero);
> +	WARN_ON(zero != 0);

Then,

WARN_ON(atomic_read(&buf->memory_used) != <local accum>);
atomic_set(&buf->memory_used, 0);

?

Regards,
Peter Hurley