Re: [PATCH 3/3 v12] printk: Add monotonic, boottime, and realtime timestamps

[Pavel Machek]

Hi!

> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index b19c491cbc4e..e21b0c002d0f 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -8,12 +8,58 @@ config PRINTK_TIME
> messages to be added to the output of the syslog() system
> call and at the console.
>  
> +choice
> + prompt "printk default clock timestamp" if PRINTK_TIME
> + default PRINTK_TIME_LOCAL if PRINTK_TIME
> + help
> +   This option is selected by setting one of
> +   PRINTK_TIME_[DISABLE|LOCAL|BOOT|MONO|REAL] and causes time stamps of
> +   the printk() messages to be added to the output of the syslog()
> +   system call and at the console.
> +
> 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.
>  
> The behavior is also controlled by the kernel command line
> -   parameter printk.time=1. See 
> Documentation/admin-guide/kernel-parameters.rst
> +   parameter printk.time. See
> +   Documentation/admin-guide/kernel-parameters.rst
> +
> +config PRINTK_TIME_LOCAL
> + bool "Local Clock"
> + help
> +   Selecting this option causes the time stamps of printk() to be
> +   stamped with the unadjusted hardware clock.
> +
> +config PRINTK_TIME_BOOT
> + bool "Boot Time Clock"
> + help
> +   Selecting this option causes the time stamps of printk() to be
> +   stamped with the adjusted boottime clock.
> +
> +config PRINTK_TIME_MONO
> + bool "Monotonic Clock"
> + help
> +   Selecting this option causes the time stamps of printk() to be
> +   stamped with the adjusted monotonic clock.
> +
> +config PRINTK_TIME_REAL
> + bool "Real Time Clock"
> + help
> +   Selecting this option causes the time stamps of printk() to be
> +   stamped with the adjusted realtime clock (UTC).
> +endchoice
> +
> +config PRINTK_TIME_TYPE
> + int
> + depends on PRINTK
> + range 0 4
> + default 0 if !PRINTK_TIME
> + default 1 if PRINTK_TIME_LOCAL
> + default 2 if PRINTK_TIME_BOOT
> + default 3 if PRINTK_TIME_MONO
> + default 4 if PRINTK_TIME_REAL
> +
>  
>  config CONSOLE_LOGLEVEL_DEFAULT
>   int "Default console loglevel (1-15)"

Come on, you don't need to ask user just to set default value to be
overriden by command line. This is not nearly important enough.

Drop it. You can still use CONFIG_CMDLINE="...".

Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) 
http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html


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Re: [PATCH 3/3 v12] printk: Add monotonic, boottime, and realtime timestamps

[Pavel Machek]

Hi!

> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index b19c491cbc4e..e21b0c002d0f 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -8,12 +8,58 @@ config PRINTK_TIME
> messages to be added to the output of the syslog() system
> call and at the console.
>  
> +choice
> + prompt "printk default clock timestamp" if PRINTK_TIME
> + default PRINTK_TIME_LOCAL if PRINTK_TIME
> + help
> +   This option is selected by setting one of
> +   PRINTK_TIME_[DISABLE|LOCAL|BOOT|MONO|REAL] and causes time stamps of
> +   the printk() messages to be added to the output of the syslog()
> +   system call and at the console.
> +
> 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.
>  
> The behavior is also controlled by the kernel command line
> -   parameter printk.time=1. See 
> Documentation/admin-guide/kernel-parameters.rst
> +   parameter printk.time. See
> +   Documentation/admin-guide/kernel-parameters.rst
> +
> +config PRINTK_TIME_LOCAL
> + bool "Local Clock"
> + help
> +   Selecting this option causes the time stamps of printk() to be
> +   stamped with the unadjusted hardware clock.
> +
> +config PRINTK_TIME_BOOT
> + bool "Boot Time Clock"
> + help
> +   Selecting this option causes the time stamps of printk() to be
> +   stamped with the adjusted boottime clock.
> +
> +config PRINTK_TIME_MONO
> + bool "Monotonic Clock"
> + help
> +   Selecting this option causes the time stamps of printk() to be
> +   stamped with the adjusted monotonic clock.
> +
> +config PRINTK_TIME_REAL
> + bool "Real Time Clock"
> + help
> +   Selecting this option causes the time stamps of printk() to be
> +   stamped with the adjusted realtime clock (UTC).
> +endchoice
> +
> +config PRINTK_TIME_TYPE
> + int
> + depends on PRINTK
> + range 0 4
> + default 0 if !PRINTK_TIME
> + default 1 if PRINTK_TIME_LOCAL
> + default 2 if PRINTK_TIME_BOOT
> + default 3 if PRINTK_TIME_MONO
> + default 4 if PRINTK_TIME_REAL
> +
>  
>  config CONSOLE_LOGLEVEL_DEFAULT
>   int "Default console loglevel (1-15)"

Come on, you don't need to ask user just to set default value to be
overriden by command line. This is not nearly important enough.

Drop it. You can still use CONFIG_CMDLINE="...".

Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) 
http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html


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Re: [PATCH 3/3 v12] printk: Add monotonic, boottime, and realtime timestamps

[Prarit Bhargava]

On 09/26/2017 07:48 AM, Petr Mladek wrote:
> On Mon 2017-09-18 13:51:00, Prarit Bhargava wrote:
>> printk.time=1/CONFIG_PRINTK_TIME=1 adds a unmodified local hardware clock
>> timestamp to printk messages.  The local hardware clock loses time each
>> day making it difficult to determine exactly when an issue has occurred in
>> the kernel log, and making it difficult to determine how kernel and
>> hardware issues relate to each other in real time.
>>
>> Make printk output different timestamps by adding options for no
>> timestamp, the local hardware clock, the monotonic clock, the boottime
>> clock, and the real clock.  Allow a user to pick one of the clocks by
>> using the printk.time kernel parameter.  Output the type of clock in
>> /sys/module/printk/parameters/time so userspace programs can interpret the
>> timestamp.
>>
>> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
>> index 512f7c2baedd..5e0bf2ef02f7 100644
>> --- a/kernel/printk/printk.c
>> +++ b/kernel/printk/printk.c
>> @@ -1201,14 +1204,130 @@ static inline void boot_delay_msec(int level)
>> +static int printk_time = CONFIG_PRINTK_TIME_TYPE;
>> +
>> +static int printk_set_ts_source(enum timestamp_sources ts_source)
>> +{
>> +int err = 0;
> 
> 
>> @@ -1861,6 +1980,7 @@ static size_t msg_print_text(const struct printk_log 
>> *msg,
>>   bool syslog, char *buf, size_t size) { return 0; }
>>  static bool suppress_message_printing(int level) { return false; }
>>  
>> +static int printk_time;
> 
> I worried if the variable should have got initialized. But it seems to
> be a relic from an older version. The variable is not longer used and
> needed when CONFIG_PRINTK is not defined. It is proved by gcc:
> 
>   CC  kernel/printk/printk.o
> kernel/printk/printk.c:1983:12: warning: ‘printk_time’ defined but not used 
> [-Wunused-variable]
>  static int printk_time;
> 

I didn't catch that :(.  tglx, want a v14?

P.

> 
>>  #endif /* CONFIG_PRINTK */
>>  
>>  #ifdef CONFIG_EARLY_PRINTK
> 
> Otherwise that patch looks fine. With the unused variable removed,
> feel free to use:
> 
> Reviewed-by: Petr Mladek 
> 
> Best Regards,
> Petr
> 

Re: [PATCH 3/3 v12] printk: Add monotonic, boottime, and realtime timestamps

[Prarit Bhargava]

On 09/26/2017 07:48 AM, Petr Mladek wrote:
> On Mon 2017-09-18 13:51:00, Prarit Bhargava wrote:
>> printk.time=1/CONFIG_PRINTK_TIME=1 adds a unmodified local hardware clock
>> timestamp to printk messages.  The local hardware clock loses time each
>> day making it difficult to determine exactly when an issue has occurred in
>> the kernel log, and making it difficult to determine how kernel and
>> hardware issues relate to each other in real time.
>>
>> Make printk output different timestamps by adding options for no
>> timestamp, the local hardware clock, the monotonic clock, the boottime
>> clock, and the real clock.  Allow a user to pick one of the clocks by
>> using the printk.time kernel parameter.  Output the type of clock in
>> /sys/module/printk/parameters/time so userspace programs can interpret the
>> timestamp.
>>
>> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
>> index 512f7c2baedd..5e0bf2ef02f7 100644
>> --- a/kernel/printk/printk.c
>> +++ b/kernel/printk/printk.c
>> @@ -1201,14 +1204,130 @@ static inline void boot_delay_msec(int level)
>> +static int printk_time = CONFIG_PRINTK_TIME_TYPE;
>> +
>> +static int printk_set_ts_source(enum timestamp_sources ts_source)
>> +{
>> +int err = 0;
> 
> 
>> @@ -1861,6 +1980,7 @@ static size_t msg_print_text(const struct printk_log 
>> *msg,
>>   bool syslog, char *buf, size_t size) { return 0; }
>>  static bool suppress_message_printing(int level) { return false; }
>>  
>> +static int printk_time;
> 
> I worried if the variable should have got initialized. But it seems to
> be a relic from an older version. The variable is not longer used and
> needed when CONFIG_PRINTK is not defined. It is proved by gcc:
> 
>   CC  kernel/printk/printk.o
> kernel/printk/printk.c:1983:12: warning: ‘printk_time’ defined but not used 
> [-Wunused-variable]
>  static int printk_time;
> 

I didn't catch that :(.  tglx, want a v14?

P.

> 
>>  #endif /* CONFIG_PRINTK */
>>  
>>  #ifdef CONFIG_EARLY_PRINTK
> 
> Otherwise that patch looks fine. With the unused variable removed,
> feel free to use:
> 
> Reviewed-by: Petr Mladek 
> 
> Best Regards,
> Petr
> 

Re: [PATCH 3/3 v12] printk: Add monotonic, boottime, and realtime timestamps

[Petr Mladek]

On Mon 2017-09-18 13:51:00, Prarit Bhargava wrote:
> printk.time=1/CONFIG_PRINTK_TIME=1 adds a unmodified local hardware clock
> timestamp to printk messages.  The local hardware clock loses time each
> day making it difficult to determine exactly when an issue has occurred in
> the kernel log, and making it difficult to determine how kernel and
> hardware issues relate to each other in real time.
> 
> Make printk output different timestamps by adding options for no
> timestamp, the local hardware clock, the monotonic clock, the boottime
> clock, and the real clock.  Allow a user to pick one of the clocks by
> using the printk.time kernel parameter.  Output the type of clock in
> /sys/module/printk/parameters/time so userspace programs can interpret the
> timestamp.
> 
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> index 512f7c2baedd..5e0bf2ef02f7 100644
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -1201,14 +1204,130 @@ static inline void boot_delay_msec(int level)
> +static int printk_time = CONFIG_PRINTK_TIME_TYPE;
> +
> +static int printk_set_ts_source(enum timestamp_sources ts_source)
> +{
> + int err = 0;


> @@ -1861,6 +1980,7 @@ static size_t msg_print_text(const struct printk_log 
> *msg,
>bool syslog, char *buf, size_t size) { return 0; }
>  static bool suppress_message_printing(int level) { return false; }
>  
> +static int printk_time;

I worried if the variable should have got initialized. But it seems to
be a relic from an older version. The variable is not longer used and
needed when CONFIG_PRINTK is not defined. It is proved by gcc:

  CC  kernel/printk/printk.o
kernel/printk/printk.c:1983:12: warning: ‘printk_time’ defined but not used 
[-Wunused-variable]
 static int printk_time;


>  #endif /* CONFIG_PRINTK */
>  
>  #ifdef CONFIG_EARLY_PRINTK

Otherwise that patch looks fine. With the unused variable removed,
feel free to use:

Reviewed-by: Petr Mladek 

Best Regards,
Petr

Re: [PATCH 3/3 v12] printk: Add monotonic, boottime, and realtime timestamps

[Petr Mladek]

On Mon 2017-09-18 13:51:00, Prarit Bhargava wrote:
> printk.time=1/CONFIG_PRINTK_TIME=1 adds a unmodified local hardware clock
> timestamp to printk messages.  The local hardware clock loses time each
> day making it difficult to determine exactly when an issue has occurred in
> the kernel log, and making it difficult to determine how kernel and
> hardware issues relate to each other in real time.
> 
> Make printk output different timestamps by adding options for no
> timestamp, the local hardware clock, the monotonic clock, the boottime
> clock, and the real clock.  Allow a user to pick one of the clocks by
> using the printk.time kernel parameter.  Output the type of clock in
> /sys/module/printk/parameters/time so userspace programs can interpret the
> timestamp.
> 
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> index 512f7c2baedd..5e0bf2ef02f7 100644
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -1201,14 +1204,130 @@ static inline void boot_delay_msec(int level)
> +static int printk_time = CONFIG_PRINTK_TIME_TYPE;
> +
> +static int printk_set_ts_source(enum timestamp_sources ts_source)
> +{
> + int err = 0;


> @@ -1861,6 +1980,7 @@ static size_t msg_print_text(const struct printk_log 
> *msg,
>bool syslog, char *buf, size_t size) { return 0; }
>  static bool suppress_message_printing(int level) { return false; }
>  
> +static int printk_time;

I worried if the variable should have got initialized. But it seems to
be a relic from an older version. The variable is not longer used and
needed when CONFIG_PRINTK is not defined. It is proved by gcc:

  CC  kernel/printk/printk.o
kernel/printk/printk.c:1983:12: warning: ‘printk_time’ defined but not used 
[-Wunused-variable]
 static int printk_time;


>  #endif /* CONFIG_PRINTK */
>  
>  #ifdef CONFIG_EARLY_PRINTK

Otherwise that patch looks fine. With the unused variable removed,
feel free to use:

Reviewed-by: Petr Mladek 

Best Regards,
Petr

[PATCH 3/3 v12] printk: Add monotonic, boottime, and realtime timestamps

[Prarit Bhargava]

printk.time=1/CONFIG_PRINTK_TIME=1 adds a unmodified local hardware clock
timestamp to printk messages.  The local hardware clock loses time each
day making it difficult to determine exactly when an issue has occurred in
the kernel log, and making it difficult to determine how kernel and
hardware issues relate to each other in real time.

Make printk output different timestamps by adding options for no
timestamp, the local hardware clock, the monotonic clock, the boottime
clock, and the real clock.  Allow a user to pick one of the clocks by
using the printk.time kernel parameter.  Output the type of clock in
/sys/module/printk/parameters/time so userspace programs can interpret the
timestamp.

v2: Use peterz's suggested Kconfig options.  Merge patchset together.
Fix i386 !CONFIG_PRINTK builds.

v3: Fixed x86_64_defconfig. Added printk_time_type enum and
printk_time_str for better output. Added BOOTTIME clock functionality.

v4: Fix messages, add additional printk.time options, and fix configs.

v5: Renaming of structures, and allow printk_time_set() to
evaluate substrings of entries (eg: allow 'r', 'real', 'realtime').  From
peterz, make fast functions return 0 until timekeeping is initialized
(removes timekeeping_active & ktime_get_boot|real_log_ts() suggested by
 tglx and adds ktime_get_real_offset()).  Switch to a function pointer
for printk_get_ts() and reference fast functions.  Make timestamp_sources enum
match choice options for CONFIG_PRINTK_TIME (adds PRINTK_TIME_UNDEFINED).

v6: Define PRINTK_TIME_UNDEFINED for !CONFIG_PRINTK builds.  Separate
timekeeping changes into separate patch.  Minor include file cleanup.

v7: Add default case to printk_set_timestamp() and add PRINTK_TIME_DEBUG
for users that want to set timestamp to different values during runtime.
Add jstultz' Kconfig to avoid defconfig churn.

v8: Add CONFIG_PRINTK_TIME_DEBUG to allow timestamp runtime switching.
Rename PRINTK_TIME_DISABLE to PRINTK_TIME_DISABLED.  Rename
printk_set_timestamp() to printk_set_ts_func().  Separate
printk_set_ts_func() and printk_get_first_ts() portions.  Rename param
functions.  Adjust configs, enum, and timestamp_sources_str to be 0-4.
Add mention realtime clock is UTC in Documentation.

v9: Fix typo.  Add __ktime_get_real_fast_ns_unsafe().

v10: Remove time parameter restrictions.

v11: Rework using tglx's real time patch

v12: Reword Kconfig names.  Simplify timestamp logic and remove
recursive code.

Signed-off-by: Prarit Bhargava 
Cc: Mark Salyzyn 
Cc: Jonathan Corbet 
Cc: Petr Mladek 
Cc: Sergey Senozhatsky 
Cc: Steven Rostedt 
Cc: John Stultz 
Cc: Thomas Gleixner 
Cc: Stephen Boyd 
Cc: Andrew Morton 
Cc: Greg Kroah-Hartman 
Cc: "Paul E. McKenney" 
Cc: Christoffer Dall 
Cc: Deepa Dinamani 
Cc: Ingo Molnar 
Cc: Joel Fernandes 
Cc: Prarit Bhargava 
Cc: Kees Cook 
Cc: Peter Zijlstra 
Cc: Geert Uytterhoeven 
Cc: "Luis R. Rodriguez" 
Cc: Nicholas Piggin 
Cc: "Jason A. Donenfeld" 
Cc: Olof Johansson 
Cc: Josh Poimboeuf 
Cc: linux-...@vger.kernel.org
[jstultz: reworked Kconfig settings to avoid defconfig noise]
Signed-off-by: John Stultz 
---
 Documentation/admin-guide/kernel-parameters.txt |   6 +-
 kernel/printk/printk.c  | 130 +++-
 lib/Kconfig.debug   |  48 -
 3 files changed, 176 insertions(+), 8 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt 
b/Documentation/admin-guide/kernel-parameters.txt
index 05496622b4ef..9a84483db403 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3211,8 +3211,10 @@
ratelimit - ratelimit the logging
Default: ratelimit
 
-   printk.time=Show timing data prefixed to each printk message line
-   Format:   (1/Y/y=enable, 0/N/n=disable)
+   printk.time=Show timestamp prefixed to each printk message line
+   Format: 
+   (0/N/n/disable, 1/Y/y/local,
+b/boot, m/monotonic, r/realtime (in UTC))
 
processor.max_cstate=   [HW,ACPI]
Limit processor to maximum C-state
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 512f7c2baedd..5e0bf2ef02f7 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -576,6 +576,9 @@ static u32 truncate_msg(u16 

[PATCH 3/3 v12] printk: Add monotonic, boottime, and realtime timestamps

[Prarit Bhargava]

printk.time=1/CONFIG_PRINTK_TIME=1 adds a unmodified local hardware clock
timestamp to printk messages.  The local hardware clock loses time each
day making it difficult to determine exactly when an issue has occurred in
the kernel log, and making it difficult to determine how kernel and
hardware issues relate to each other in real time.

Make printk output different timestamps by adding options for no
timestamp, the local hardware clock, the monotonic clock, the boottime
clock, and the real clock.  Allow a user to pick one of the clocks by
using the printk.time kernel parameter.  Output the type of clock in
/sys/module/printk/parameters/time so userspace programs can interpret the
timestamp.

v2: Use peterz's suggested Kconfig options.  Merge patchset together.
Fix i386 !CONFIG_PRINTK builds.

v3: Fixed x86_64_defconfig. Added printk_time_type enum and
printk_time_str for better output. Added BOOTTIME clock functionality.

v4: Fix messages, add additional printk.time options, and fix configs.

v5: Renaming of structures, and allow printk_time_set() to
evaluate substrings of entries (eg: allow 'r', 'real', 'realtime').  From
peterz, make fast functions return 0 until timekeeping is initialized
(removes timekeeping_active & ktime_get_boot|real_log_ts() suggested by
 tglx and adds ktime_get_real_offset()).  Switch to a function pointer
for printk_get_ts() and reference fast functions.  Make timestamp_sources enum
match choice options for CONFIG_PRINTK_TIME (adds PRINTK_TIME_UNDEFINED).

v6: Define PRINTK_TIME_UNDEFINED for !CONFIG_PRINTK builds.  Separate
timekeeping changes into separate patch.  Minor include file cleanup.

v7: Add default case to printk_set_timestamp() and add PRINTK_TIME_DEBUG
for users that want to set timestamp to different values during runtime.
Add jstultz' Kconfig to avoid defconfig churn.

v8: Add CONFIG_PRINTK_TIME_DEBUG to allow timestamp runtime switching.
Rename PRINTK_TIME_DISABLE to PRINTK_TIME_DISABLED.  Rename
printk_set_timestamp() to printk_set_ts_func().  Separate
printk_set_ts_func() and printk_get_first_ts() portions.  Rename param
functions.  Adjust configs, enum, and timestamp_sources_str to be 0-4.
Add mention realtime clock is UTC in Documentation.

v9: Fix typo.  Add __ktime_get_real_fast_ns_unsafe().

v10: Remove time parameter restrictions.

v11: Rework using tglx's real time patch

v12: Reword Kconfig names.  Simplify timestamp logic and remove
recursive code.

Signed-off-by: Prarit Bhargava 
Cc: Mark Salyzyn 
Cc: Jonathan Corbet 
Cc: Petr Mladek 
Cc: Sergey Senozhatsky 
Cc: Steven Rostedt 
Cc: John Stultz 
Cc: Thomas Gleixner 
Cc: Stephen Boyd 
Cc: Andrew Morton 
Cc: Greg Kroah-Hartman 
Cc: "Paul E. McKenney" 
Cc: Christoffer Dall 
Cc: Deepa Dinamani 
Cc: Ingo Molnar 
Cc: Joel Fernandes 
Cc: Prarit Bhargava 
Cc: Kees Cook 
Cc: Peter Zijlstra 
Cc: Geert Uytterhoeven 
Cc: "Luis R. Rodriguez" 
Cc: Nicholas Piggin 
Cc: "Jason A. Donenfeld" 
Cc: Olof Johansson 
Cc: Josh Poimboeuf 
Cc: linux-...@vger.kernel.org
[jstultz: reworked Kconfig settings to avoid defconfig noise]
Signed-off-by: John Stultz 
---
 Documentation/admin-guide/kernel-parameters.txt |   6 +-
 kernel/printk/printk.c  | 130 +++-
 lib/Kconfig.debug   |  48 -
 3 files changed, 176 insertions(+), 8 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt 
b/Documentation/admin-guide/kernel-parameters.txt
index 05496622b4ef..9a84483db403 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3211,8 +3211,10 @@
ratelimit - ratelimit the logging
Default: ratelimit
 
-   printk.time=Show timing data prefixed to each printk message line
-   Format:   (1/Y/y=enable, 0/N/n=disable)
+   printk.time=Show timestamp prefixed to each printk message line
+   Format: 
+   (0/N/n/disable, 1/Y/y/local,
+b/boot, m/monotonic, r/realtime (in UTC))
 
processor.max_cstate=   [HW,ACPI]
Limit processor to maximum C-state
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 512f7c2baedd..5e0bf2ef02f7 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -576,6 +576,9 @@ static u32 truncate_msg(u16 *text_len, u16 *trunc_msg_len,
return msg_used_size(*text_len + *trunc_msg_len, 0, pad_len);
 }
 
+static u64 printk_get_first_ts(void);
+static u64 (*printk_get_ts)(void) = printk_get_first_ts;
+
 /* insert record into the buffer, discard old ones, update heads */
 static int log_store(int facility, int level,
 enum log_flags flags, u64 ts_nsec,
@@ -624,7 +627,7 @@ static int log_store(int facility, int level,
if (ts_nsec > 0)
msg->ts_nsec = ts_nsec;
else
-   msg->ts_nsec =