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SubjectRe: [PATCH v2] earlycon: prevent multiple register_console()
On Thu, 02 Jun 2022 11:00:38 +0200, Michael Walle wrote:
> If the earlycon parameter is given twice, the kernel will spit out a
> WARN() in register_console() because it was already registered. The
> non-dt variant setup_earlycon() already handles that gracefully. The dt
> variant of_setup_earlycon() doesn't. Add the check there and add the
> -EALREADY handling in early_init_dt_scan_chosen_stdout().
>
> FWIW, this doesn't happen if CONFIG_ACPI_SPCR_TABLE is set. In that case
> the registration is delayed until after earlycon parameter(s) are
> parsed.
>
> Signed-off-by: Michael Walle <michael@walle.cc>
> ---
> changes since v1:
> - add missing EALREADY handling in of_setup_earlycon()
> - return 0 early as suggested by Rob
>
> For the curious, here is the backtrace:
>
> [ 0.000000] ------------[ cut here ]------------
> [ 0.000000] WARNING: CPU: 0 PID: 0 at kernel/printk/printk.c:3328 register_console+0x2b4/0x364
> [ 0.000000] console 'atmel_serial0' already registered
> [ 0.000000] Modules linked in:
> [ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 5.18.0-next-20220601+ #652
> [ 0.000000] Hardware name: Generic DT based system
> [ 0.000000] Backtrace:
> [ 0.000000] dump_backtrace from show_stack+0x18/0x1c
> [ 0.000000] show_stack from dump_stack_lvl+0x48/0x54
> [ 0.000000] dump_stack_lvl from dump_stack+0x18/0x1c
> [ 0.000000] dump_stack from __warn+0xd0/0x148
> [ 0.000000] __warn from warn_slowpath_fmt+0x9c/0xc4
> [ 0.000000] warn_slowpath_fmt from register_console+0x2b4/0x364
> [ 0.000000] register_console from of_setup_earlycon+0x29c/0x2ac
> [ 0.000000] of_setup_earlycon from early_init_dt_scan_chosen_stdout+0x154/0x18c
> [ 0.000000] early_init_dt_scan_chosen_stdout from param_setup_earlycon+0x40/0x48
> [ 0.000000] param_setup_earlycon from do_early_param+0x88/0xc4
> [ 0.000000] do_early_param from parse_args+0x1a4/0x404
> [ 0.000000] parse_args from parse_early_options+0x40/0x48
> [ 0.000000] parse_early_options from parse_early_param+0x38/0x48
> [ 0.000000] parse_early_param from setup_arch+0x114/0x7a4
> [ 0.000000] setup_arch from start_kernel+0x74/0x6dc
> [ 0.000000] start_kernel from 0x0
> [ 0.000000] ---[ end trace 0000000000000000 ]---
>
> drivers/of/fdt.c | 4 +++-
> drivers/tty/serial/earlycon.c | 3 +++
> 2 files changed, 6 insertions(+), 1 deletion(-)
>

Reviewed-by: Rob Herring <robh@kernel.org>

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