Messages in this thread | | | Subject | Re: [PATCH] printk: Add caller information to printk() output. | From | Tetsuo Handa <> | Date | Sat, 1 Dec 2018 23:44:37 +0900 |
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On 2018/12/01 0:40, Petr Mladek wrote: >> Some examples for console output: >> >> [ 0.293000] [T1] smpboot: CPU0: Intel(R) Core(TM) i5-4440S CPU @ 2.80GHz (family: 0x6, model: 0x3c, stepping: 0x3) >> [ 0.299733] [T1] Performance Events: Haswell events, core PMU driver. >> [ 2.813808] [T35] clocksource: Switched to clocksource tsc >> [ 2.893984] [C0] random: fast init done > ^ > > Please, remove the space between the timestamp and the from field.
This space was emitted by print_time(). Do we want to modify print_time() not to emit this space if the from field is printed?
If we modify print_time(), I think that the leading spaces inserted by "%5lu" makes little sense, for "%5lu" is too small for systems with uptime >= 1.16 days and parsers after all cannot assume fixed length for the timestamp field. Then, we could change from "%5lu.%06lu" to "%lu.%06lu" so that parsers (like /bin/awk) can get prefix part using white spaces as a delimiter.
If we want to reduce space, do we want to do like
[0.293000@T1] smpboot: CPU0: Intel(R) Core(TM) i5-4440S CPU @ 2.80GHz (family: 0x6, model: 0x3c, stepping: 0x3) [0.299733@T1] Performance Events: Haswell events, core PMU driver. [2.813808@T35] clocksource: Switched to clocksource tsc [2.893984@C0] random: fast init done
(if printk_time = true) or
[@T1] smpboot: CPU0: Intel(R) Core(TM) i5-4440S CPU @ 2.80GHz (family: 0x6, model: 0x3c, stepping: 0x3) [@T1] Performance Events: Haswell events, core PMU driver. [@T35] clocksource: Switched to clocksource tsc [@C0] random: fast init done
(if printk_time = false) ?
Dmitry, what format/delimiter is convenient for parsing by syzbot?
>> @@ -1037,6 +1054,9 @@ void log_buf_vmcoreinfo_setup(void) >> VMCOREINFO_OFFSET(printk_log, len); >> VMCOREINFO_OFFSET(printk_log, text_len); >> VMCOREINFO_OFFSET(printk_log, dict_len); >> +#ifdef CONFIG_PRINTK_FROM >> + VMCOREINFO_OFFSET(printk_log, from_id); >> +#endif > > The crash tool would need to be updated if anyone wanted to read > the log from the extended structure. Well, it might be done later > if people start using it more widely.
Since syzbot can utilize output from only normal consoles, I can keep extended records unmodified for now.
> > I think about adding one more filed "u8 version". It would help > to solve the external compatibility in the long term.
/dev/kmsg format allows adding more fields, but that format did not define how to tell what fields are there. If fields are conditionally added by kernel config options, I don't think that "u8 version" field helps. Unless we add fields unconditionally, we will need to use $name=$value (where $name and $value must not contain ',' and ';') representation.
> Anyway, I like this feature. It is compatible with /dev/kmsg > format. dmesg works well. It helps to sort any mixed output > from both full and continuous lines.
OK, let's refine this approach.
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