Messages in this thread | | | Subject | Re: [PATCH] printk: Add loglevel for "do not print to consoles". | From | Tetsuo Handa <> | Date | Wed, 29 Apr 2020 01:23:15 +0900 |
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On 2020/04/29 0:45, Michal Hocko wrote: > On Tue 28-04-20 22:11:19, Tetsuo Handa wrote: >> Existing KERN_$LEVEL allows a user to determine whether he/she wants that message >> to be printed on consoles (even if it spams his/her operation doing on consoles), and >> at the same time constrains that user whether that message is saved to log files. >> KERN_NO_CONSOLES allows a user to control whether he/she wants that message to be >> saved to log files (without spamming his/her operation doing on consoles). > > I understand that. But how do I know whether the user considers the > particular information important enough to be dumped on the console. > This sounds like a policy in the kernel to me.
I'm still unable to understand your question.
> I simply cannot forsee > any console configuration to tell whether my information is going to > swamp the console to no use or not.
Neither can I.
> Compare that to KERN_$LEVEL instead. > I know that an information is of low/high importance. It is the user > policy to decide and base some filtering on top of that priority.
Whether to use KERN_NO_CONSOLES is not per-importance basis but per-content basis.
Since both pr_info("[%7d] %5d %5d %8lu %8lu %8ld %8lu %5hd %s\n", ...) from dump_tasks() and pr_info("oom-kill:constraint=%s,nodemask=%*pbl", ...) from dump_oom_summary() use KERN_INFO importance, existing KERN_$LEVEL-based approach cannot handle these messages differently. Since changing the former to e.g. KERN_DEBUG will cause userspace to discard the messages, we effectively can't change KERN_$LEVEL. If the kernel allows the former to use KERN_NO_CONSOLES in addition to KERN_INFO, the administrator can select from two choices: printing "both the former and the latter" or "only the latter" to consoles.
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