Subject: Re: linux-next: manual merge of the tty tree with the tty.current tree

From: Greg KH <[email-masked]>
Date: Tue, 23 Apr 2024 13:24:50 +0200

On Fri, Apr 19, 2024 at 02:19:47PM +1000, Stephen Rothwell wrote:
> Hi all,
> 
> Today's linux-next merge of the tty tree got a conflict in:
> 
>   drivers/tty/serial/serial_core.c
> 
> between commit:
> 
>   9cf7ea2eeb74 ("serial: core: Clearing the circular buffer before NULLifying it")
> 
> from the tty.current tree and commits:
> 
>   1788cf6a91d9 ("tty: serial: switch from circ_buf to kfifo")
>   abcd8632f26b ("serial: core: Extract uart_alloc_xmit_buf() and uart_free_xmit_buf()")
> 
> from the tty tree.
> 
> I fixed it up (see below) and can carry the fix as necessary. This
> is now fixed as far as linux-next is concerned, but any non trivial
> conflicts should be mentioned to your upstream maintainer when your tree
> is submitted for merging.  You may also want to consider cooperating
> with the maintainer of the conflicting tree to minimise any particularly
> complex conflicts.
> 
> -- 
> Cheers,
> Stephen Rothwell
> 
> diff --cc drivers/tty/serial/serial_core.c
> index c476d884356d,b9d631037ff6..000000000000
> --- a/drivers/tty/serial/serial_core.c
> +++ b/drivers/tty/serial/serial_core.c
> @@@ -285,6 -273,53 +273,54 @@@ static int uart_alloc_xmit_buf(struct t
>   		free_page(page);
>   	}
>   
> + 	return 0;
> + }
> + 
> + static void uart_free_xmit_buf(struct tty_port *port)
> + {
> + 	struct uart_state *state = container_of(port, struct uart_state, port);
> + 	struct uart_port *uport;
> + 	unsigned long flags;
> + 	char *xmit_buf;
> + 
> + 	/*
> + 	 * Do not free() the transmit buffer page under the port lock since
> + 	 * this can create various circular locking scenarios. For instance,
> + 	 * console driver may need to allocate/free a debug object, which
> + 	 * can end up in printk() recursion.
> + 	 */
> + 	uport = uart_port_lock(state, flags);
> ++	kfifo_reset(&state->port.xmit_fifo);
> + 	xmit_buf = port->xmit_buf;
> + 	port->xmit_buf = NULL;
> + 	INIT_KFIFO(port->xmit_fifo);

The INIT_KFIFO() call here does the same (same plus more) than the
kfifo_reset() call does, so I'll just drop the kfifo_reset() here and
all should be fine.  I'll do this in my tree now, thanks.

greg k-h