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

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Message-ID: <c62ac962-0368-7667-de3e-1f97f4d5b032@redhat.com>
Date:   Tue, 26 Sep 2017 08:55:25 -0400
From:   Prarit Bhargava <prarit@...hat.com>
To:     Petr Mladek <pmladek@...e.com>
Cc:     linux-kernel@...r.kernel.org, Mark Salyzyn <salyzyn@...roid.com>,
        Jonathan Corbet <corbet@....net>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        John Stultz <john.stultz@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Christoffer Dall <cdall@...aro.org>,
        Deepa Dinamani <deepa.kernel@...il.com>,
        Ingo Molnar <mingo@...nel.org>,
        Joel Fernandes <joelaf@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        "Luis R. Rodriguez" <mcgrof@...nel.org>,
        Nicholas Piggin <npiggin@...il.com>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        Olof Johansson <olof@...om.net>,
        Josh Poimboeuf <jpoimboe@...hat.com>, linux-doc@...r.kernel.org
Subject: Re: [PATCH 3/3 v12] printk: Add monotonic, boottime, and realtime
 timestamps



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 <pmladek@...e.com>
> 
> Best Regards,
> Petr
>