Commit 3ec25826 authored Apr 12, 2019 by Paul Gortmaker Committed by Petr Mladek Apr 15, 2019

printk: Tie printk_once / printk_deferred_once into .data.once for reset

In commit b1fca27d ("kernel debug: support resetting WARN*_ONCE")
we got the opportunity to reset state on the one shot messages,
without having to reboot.

However printk_once (printk_deferred_once) live in a different file
and didn't get the same kind of update/conversion, so they remain
unconditionally one shot, until the system is rebooted.

For example, we currently have:

  sched/rt.c: printk_deferred_once("sched: RT throttling activated\n");

..which could reasonably be tripped as someone is testing and tuning
a new system/workload and their task placements.  For consistency, and
to avoid reboots in the same vein as the original commit, we make these
two instances of _once the same as the WARN*_ONCE instances are.

Link: http://lkml.kernel.org/r/1555121491-31213-1-git-send-email-paul.gortmaker@windriver.com


Cc: Andi Kleen <ak@linux.intel.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>

parent 2821fd0c

Documentation/clearing-warn-once.txt

+1 −1

Original line number	Diff line number	Diff line

		WARN_ONCE / WARN_ON_ONCE only print a warning once.
		WARN_ONCE / WARN_ON_ONCE / printk_once only emit a message once.

		echo 1 > /sys/kernel/debug/clear_warn_once

include/linux/printk.h

+2 −2

Original line number	Diff line number	Diff line
		@@ -347,7 +347,7 @@ extern int kptr_restrict;
		#ifdef CONFIG_PRINTK
		#define printk_once(fmt, ...) \
		({ \
		static bool __print_once __read_mostly; \
		static bool __section(.data.once) __print_once; \
		bool __ret_print_once = !__print_once; \
		\
		if (!__print_once) { \
		@@ -358,7 +358,7 @@ extern int kptr_restrict;
		})
		#define printk_deferred_once(fmt, ...) \
		({ \
		static bool __print_once __read_mostly; \
		static bool __section(.data.once) __print_once; \
		bool __ret_print_once = !__print_once; \
		\
		if (!__print_once) { \

Admin message