| Message ID | 20220602090038.3201897-1-michael@walle.cc |
|---|---|
| State | New |
| Headers | show |
| Series | [v2] earlycon: prevent multiple register_console() | expand |
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>
diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c index a8f5b6532165..043b12be22d6 100644 --- a/drivers/of/fdt.c +++ b/drivers/of/fdt.c @@ -1025,6 +1025,7 @@ int __init early_init_dt_scan_chosen_stdout(void) int l; const struct earlycon_id *match; const void *fdt = initial_boot_params; + int ret; offset = fdt_path_offset(fdt, "/chosen"); if (offset < 0) @@ -1057,7 +1058,8 @@ int __init early_init_dt_scan_chosen_stdout(void) if (fdt_node_check_compatible(fdt, offset, match->compatible)) continue; - if (of_setup_earlycon(match, offset, options) == 0) + ret = of_setup_earlycon(match, offset, options); + if (!ret || ret == -EALREADY) return 0; } return -ENODEV; diff --git a/drivers/tty/serial/earlycon.c b/drivers/tty/serial/earlycon.c index 57c70851f22a..88d08ba1ca83 100644 --- a/drivers/tty/serial/earlycon.c +++ b/drivers/tty/serial/earlycon.c @@ -253,6 +253,9 @@ int __init of_setup_earlycon(const struct earlycon_id *match, bool big_endian; u64 addr; + if (early_con.flags & CON_ENABLED) + return -EALREADY; + spin_lock_init(&port->lock); port->iotype = UPIO_MEM; addr = of_flat_dt_translate_address(node);
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(-)