linux-kernel - Re: [PATCH] printk: Add caller information to printk() output.

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Message-ID: <20181207053101.GA3729@jagdpanzerIV>
Date:   Fri, 7 Dec 2018 14:31:01 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Petr Mladek <pmladek@...e.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        syzkaller <syzkaller@...glegroups.com>
Subject: Re: [PATCH] printk: Add caller information to printk() output.

On (12/07/18 13:58), Tetsuo Handa wrote:
> >                  All you need is a way to reconstruct a message around
> > some very specific place in the log - say in a range [-500, +500] lines,
> > assuming that a backtrace you are trying to reconstruct is badly fragmented.
> > I think, even 3 lower digits of a PID should do the trick.
> 
> 3 lower digits is insufficient for reconstructing PID of interest; it can
> conflict at 1/1000 probability.

OK. So you want to "trace" PID, not just a way to reconstruct fragmented
backtraces in particular places of a serial log file; that's a different
story.

> [15.922239TABI/] e1000: ens32 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: None
> [15.923927TABYb] IPv6: ADDRCONF(NETDEV_UP): ens32: link is not ready
> [15.930537TABI/] IPv6: ADDRCONF(NETDEV_CHANGE): ens32: link becomes ready
> [40.506011CAAAA] random: crng init done
> [926.716687TAAAB] reboot: Power down
> ----------------------------------------

Please, no.

PIDs, fixed size area, human readable. Just like Petr suggested.

[  123.12312][    T234] apic: boom

	-ss