Petr Mladek <pmla...@suse.com> writes: > On Thu 2019-03-21 13:59:53, Michael Ellerman wrote: >> Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp> writes: >> ... >> > From 91f85d2bd494df2f73c605d8b4747e8cc0a61ae2 Mon Sep 17 00:00:00 2001 >> > From: Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp> >> > Date: Tue, 18 Dec 2018 05:53:04 +0900 >> > Subject: [PATCH] printk: Add caller information to printk() output. >> > >> > Sometimes we want to print a series of printk() messages to consoles >> > without being disturbed by concurrent printk() from interrupts and/or >> > other threads. But we can't enforce printk() callers to use their local >> > buffers because we need to ask them to make too much changes. Also, even >> > buffering up to one line inside printk() might cause failing to emit >> > an important clue under critical situation. >> > >> > Therefore, instead of trying to help buffering, let's try to help >> > reconstructing messages by saving caller information as of calling >> > log_store() and adding it as "[T$thread_id]" or "[C$processor_id]" >> > upon printing to consoles. >> > >> > Some examples for console output: >> > >> > [ 1.222773][ T1] x86: Booting SMP configuration: >> > [ 2.779635][ T1] pci 0000:00:01.0: PCI bridge to [bus 01] >> > [ 5.069193][ T268] Fusion MPT base driver 3.04.20 >> > [ 9.316504][ C2] random: fast init done >> > [ 13.413336][ T3355] Initialized host personality >> > >> > Some examples for /dev/kmsg output: >> > >> > 6,496,1222773,-,caller=T1;x86: Booting SMP configuration: >> > 6,968,2779635,-,caller=T1;pci 0000:00:01.0: PCI bridge to [bus 01] >> > SUBSYSTEM=pci >> > DEVICE=+pci:0000:00:01.0 >> > 6,1353,5069193,-,caller=T268;Fusion MPT base driver 3.04.20 >> > 5,1526,9316504,-,caller=C2;random: fast init done >> > 6,1575,13413336,-,caller=T3355;Initialized host personality >> > >> > Note that this patch changes max length of messages which can be printed >> > by printk() or written to /dev/kmsg interface from 992 bytes to 976 bytes, >> > based on an assumption that userspace won't try to write messages hitting >> > that border line to /dev/kmsg interface. >> >> Do you have any plans to update dmesg or other userspace tools to show >> the caller information? > > dmesg already works via the syslog interface, try dmesg -S.
Oh nice, thanks. > The current implementation does not pass the information into > the /dev/kmsg interface. It has the following format: > > "<level>,<sequnum>,<timestamp>,<contflag>[,additional_values, ... > ];<message text>\n" > > It would be possible to add it as an additional value. To be hones > I am not sure how they are handled by userspace tools. OK, yeah I guess there's the potential for a backward compatibility can of worms there. I'm happy with dmesg -S :) cheers
