Re: [PATCH 2/2] printk: Add boottime and real timestamps

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On 07/25/2017 06:00 AM, Peter Zijlstra wrote:
On Tue, Jul 25, 2017 at 08:17:27AM -0400, Prarit Bhargava wrote:
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 5b1662ec546f..6cd38a25f8ea 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1,8 +1,8 @@
  menu "printk and dmesg options"
config PRINTK_TIME
-	int "Show timing information on printks (0-1)"
-	range 0 1
+	int "Show timing information on printks (0-3)"
+	range 0 3
  	default "0"
  	depends on PRINTK
  	help
@@ -13,7 +13,8 @@ config PRINTK_TIME
  	  The timestamp is always recorded internally, and exported
  	  to /dev/kmsg. This flag just specifies if the timestamp should
  	  be included, not that the timestamp is recorded. 0 disables the
-	  timestamp and 1 uses the local clock.
+	  timestamp and 1 uses the local clock, 2 uses the monotonic clock, and
+	  3 uses real clock.
The behavior is also controlled by the kernel command line
  	  parameter printk.time=1. See Documentation/admin-guide/kernel-parameters.rst

choice
	prompt "printk default clock"
	default PRIMTK_TIME_DISABLE
	help
	 goes here

	config PRINTK_TIME_DISABLE
	bool "Disabled"
	help
	 goes here

	config PRINTK_TIME_LOCAL
	bool "local clock"
	help
	 goes here

	config PRINTK_TIME_MONO
	bool "CLOCK_MONOTONIC"
	help
	 goes here

	config PRINTK_TIME_REAL
	bool "CLOCK_REALTIME"
	help
	 goes here

endchoice

config PRINTK_TIME
	int
	default 0 if PRINTK_TIME_DISABLE
	default 1 if PRINTK_TIME_LOCAL
	default 2 if PRINTK_TIME_MONO
	default 3 if PRINTK_TIME_REAL


Although I must strongly discourage using REALTIME, DST will make
untangling your logs an absolute nightmare. I would simply not provide
it.

I agree with using select, ensures only valid values are landed. It does mean that CONFIG_PRINTK_TIME in-effect gets deprecated.

REALTIME is always UTC in the kernel.

What about BOOTTIME?

-- Mark

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