Messages in this thread | | | Date | Thu, 19 Mar 2020 17:01:56 +0900 | From | Sergey Senozhatsky <> | Subject | Re: [RFC PATCH 3/3] watchdog: Turn console verbosity on when reporting softlockup |
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On (20/03/19 03:38), Valdis Klētnieks wrote: > On Thu, 19 Mar 2020 15:48:36 +0900, Sergey Senozhatsky said: > > > So the issue is that when we bump `console_loglevel' or `ignore_loglevel' > > we lift restrictions globally. For all CPUs, for all contexts which call > > printk(). This may have negative impact. Fuzzing is one example. It > > usually generates a lot of printk() noise, so lifting global printk() > > log_level restrictions does cause problems. I recall that fuzzing people > > really disliked the > > old_level = console_loglevel > > console_loglevel = new_level > > .... > > console_loglevel = old_level > > > > approach. Because if lets all CPUs and tasks to pollute serial logs. > > While what we want is to print messages from a particular CPU/task. > > Well... how does this sound for a RFC idea? We already have CONFIG_PRINTK_TIME > and CONFIG_PRINTK_CALLER. How about adding an option to allow printing the > calling CPU as well, or just extend CALLER to print [pid/cpu] rather than just > [pid]?
IIRC, CONFIG_PRINTK_CALLER prints pid when printk() caller is a running task, and CPU-id otherwise.
It was added by fuzzing people, because it's almost (or "simply") impossible to get through serial logs sometimes.
-ss
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