From 10102a890b543a8a08457dc69fa55bc032403c7d Mon Sep 17 00:00:00 2001 From: Dmitry Safonov Date: Tue, 27 Jul 2021 14:06:35 +0100 Subject: printk: Add printk.console_no_auto_verbose boot parameter console_verbose() increases console loglevel to CONSOLE_LOGLEVEL_MOTORMOUTH, which provides more information to debug a panic/oops. Unfortunately, in Arista we maintain some DUTs (Device Under Test) that are configured to have 9600 baud rate. While verbose console messages have their value to post-analyze crashes, on such setup they: - may prevent panic/oops messages being printed - take too long to flush on console resulting in watchdog reboot In all our setups we use kdump which saves dmesg buffer after panic, so in reality those extra messages on console provide no additional value, but rather add risk of not getting to __crash_kexec(). Provide printk.console_no_auto_verbose boot parameter, which allows to switch off printk being verbose on oops/panic/lockdep. Cc: Andrew Morton Cc: John Ogness Cc: Petr Mladek Cc: Sergey Senozhatsky Cc: Steven Rostedt Signed-off-by: Dmitry Safonov Suggested-by: Petr Mladek Reviewed-by: Sergey Senozhatsky Reviewed-by: Petr Mladek Tested-by: Petr Mladek Signed-off-by: Petr Mladek Link: https://lore.kernel.org/r/20210727130635.675184-3-dima@arista.com --- Documentation/admin-guide/kernel-parameters.txt | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'Documentation/admin-guide') diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 26453f250683..fdd80888217a 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -4101,6 +4101,15 @@ Format: (1/Y/y=enable, 0/N/n=disable) default: disabled + printk.console_no_auto_verbose= + Disable console loglevel raise on oops, panic + or lockdep-detected issues (only if lock debug is on). + With an exception to setups with low baudrate on + serial console, keeping this 0 is a good choice + in order to provide more debug information. + Format: + default: 0 (auto_verbose is enabled) + printk.devkmsg={on,off,ratelimit} Control writing to /dev/kmsg. on - unlimited logging to /dev/kmsg from userspace -- cgit