Messages in this thread Patch in this message | | | From | Dmitry Safonov <> | Subject | [PATCH] printk: Add CONFIG_CONSOLE_LOGLEVEL_PANIC | Date | Tue, 22 Jun 2021 15:33:50 +0100 |
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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 CONFIG_CONSOLE_LOGLEVEL_PANIC, which allows to choose how verbose the kernel must be on oops/panic.
Cc: Andrew Morton <akpm@linux-foundation.org> Cc: John Ogness <john.ogness@linutronix.de> Cc: Petr Mladek <pmladek@suse.com> Cc: Sergey Senozhatsky <senozhatsky@chromium.org> Cc: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Dmitry Safonov <dima@arista.com> --- include/linux/printk.h | 4 ++-- lib/Kconfig.debug | 13 +++++++++++++ 2 files changed, 15 insertions(+), 2 deletions(-)
diff --git a/include/linux/printk.h b/include/linux/printk.h index fe7eb2351610..5a65a719f917 100644 --- a/include/linux/printk.h +++ b/include/linux/printk.h @@ -76,8 +76,8 @@ static inline void console_silent(void) static inline void console_verbose(void) { - if (console_loglevel) - console_loglevel = CONSOLE_LOGLEVEL_MOTORMOUTH; + if (console_loglevel && (CONFIG_CONSOLE_LOGLEVEL_PANIC > 0)) + console_loglevel = CONFIG_CONSOLE_LOGLEVEL_PANIC; } /* strlen("ratelimit") + 1 */ diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 678c13967580..0c12cafd9d8b 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -61,6 +61,19 @@ config CONSOLE_LOGLEVEL_QUIET will be used as the loglevel. IOW passing "quiet" will be the equivalent of passing "loglevel=<CONSOLE_LOGLEVEL_QUIET>" +config CONSOLE_LOGLEVEL_PANIC + int "panic console loglevel (1-15)" + range 0 15 + default "15" + help + loglevel to use in kernel panic or oopses. + + Usually in order to provide more debug information on console upon + panic, one wants to see everything being printed (loglevel = 15). + With an exception to setups with low baudrate on serial console, + keeping this value high is a good choice. + 0 value is to keep the loglevel during panic/oops unchanged. + config MESSAGE_LOGLEVEL_DEFAULT int "Default message log level (1-7)" range 1 7 -- 2.31.1
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