Messages in this thread | | | From | John Ogness <> | Subject | Re: [PATCH printk v2 09/12] printk: add functions to prefer direct printing | Date | Thu, 07 Apr 2022 22:10:19 +0206 |
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On 2022-04-07, Helge Deller <deller@gmx.de> wrote: > In my case - while I debug low-level kernel code - I then just need to > use pr_warn() or pr_emerg() and get it printed non-threadened. That's > sufficient for me.
Actually, no. The loglevel does not determine if a message is direct printed or not. By "warn" I was referring to WARN_ON(condition).
If you are debugging low-level kernel code, you usually will _want_ threaded printing. The timestamps match the printk() call, so you will get accurate logs. And the runtime performance of your low-level kernel code will not be significantly affected by the printk() call.
If for some reason you really want non-threaded printing, the patch we are discussing creates new functions to manually activate it:
printk_prefer_direct_enter(); pr_info("debugging\n"); printk_prefer_direct_exit();
But then your pr_info() will cause significant latencies. The timestamp would be the same, with or without direct printing.
John
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