Hi Claudiu,
Thanks for your patch, which is now commit 3791ea69a4858b81 ("serial:
sh-sci: Clean sci_ports[0] after at earlycon exit") in tty/tty-next.
On Wed, Nov 6, 2024 at 1:02 PM Claudiu <claudiu.beznea@xxxxxxxxx> wrote:
> From: Claudiu Beznea <claudiu.beznea.uj@xxxxxxxxxxxxxx>
>
> The early_console_setup() function initializes the sci_ports[0].port with
> an object of type struct uart_port obtained from the object of type
> struct earlycon_device received as argument by the early_console_setup().
>
> It may happen that later, when the rest of the serial ports are probed,
> the serial port that was used as earlycon (e.g., port A) to be mapped to a
> different position in sci_ports[] and the slot 0 to be used by a different
> serial port (e.g., port B), as follows:
>
> sci_ports[0] = port A
> sci_ports[X] = port B
Haven't you mixed A and B?
> In this case, the new port mapped at index zero will have associated data
> that was used for earlycon.
Oops, do you have a simple reproducer for this?
> In case this happens, after Linux boot, any access to the serial port that
> maps on sci_ports[0] (port A) will block the serial port that was used as
> earlycon (port B).
Again, A <-> B?
> To fix this, add early_console_exit() that clean the sci_ports[0] at
> earlycon exit time.
>
> Fixes: 0b0cced19ab1 ("serial: sh-sci: Add CONFIG_SERIAL_EARLYCON support")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@xxxxxxxxxxxxxx>
This causes a crash (lock-up without any output) when
CONFIG_DEBUG_SPINLOCK=y (e.g. CONFIG_PROVE_LOCKING=y).
> --- a/drivers/tty/serial/sh-sci.c
> +++ b/drivers/tty/serial/sh-sci.c
> @@ -3546,6 +3546,32 @@ sh_early_platform_init_buffer("earlyprintk", &sci_driver,
> #ifdef CONFIG_SERIAL_SH_SCI_EARLYCON
> static struct plat_sci_port port_cfg __initdata;
>
> +static int early_console_exit(struct console *co)
> +{
> + struct sci_port *sci_port = &sci_ports[0];
> + struct uart_port *port = &sci_port->port;
> + unsigned long flags;
> + int locked = 1;
> +
> + if (port->sysrq)
> + locked = 0;
> + else if (oops_in_progress)
> + locked = uart_port_trylock_irqsave(port, &flags);
> + else
> + uart_port_lock_irqsave(port, &flags);
> +
> + /*
> + * Clean the slot used by earlycon. A new SCI device might
> + * map to this slot.
> + */
> + memset(sci_ports, 0, sizeof(*sci_port));
Nit: I'd rather use "*sci_port" instead of "sci_ports".
> +
> + if (locked)
> + uart_port_unlock_irqrestore(port, flags);
"BUG: spinlock bad magic", as you've just cleared the port, including
the spinlock.
I guess we can just remove all locking from this function to fix this?
However, could it happen that the new device taking slot 0 is probed
before the early console is terminated? In that case, its active
sci_ports[] entry would be cleared when early_console_exit() is called.
Also, what happens if "earlycon keep_bootcon" is passed on the kernel
command line, and the new device takes slot 0?
Thanks!
> +
> + return 0;
> +}
> +
> static int __init early_console_setup(struct earlycon_device *device,
> int type)
> {
> @@ -3562,6 +3588,8 @@ static int __init early_console_setup(struct earlycon_device *device,
> SCSCR_RE | SCSCR_TE | port_cfg.scscr);
>
> device->con->write = serial_console_write;
> + device->con->exit = early_console_exit;
> +
> return 0;
> }
> static int __init sci_early_console_setup(struct earlycon_device *device,
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
