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Re: [PATCH v5 1/4] printk/nmi: generic solution for safe printk in NMI

From Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Newsgroups linux.kernel
Subject Re: [PATCH v5 1/4] printk/nmi: generic solution for safe printk in NMI
Date 2017-04-28 03:40 +0200
Message-ID <tB333-Ac-7@gated-at.bofh.it> (permalink)
References (1 earlier) <rqlhn-8vU-3@gated-at.bofh.it> <ty1qO-6bq-33@gated-at.bofh.it> <tyb6N-3Js-13@gated-at.bofh.it> <tyka5-XM-19@gated-at.bofh.it> <tAUj8-338-23@gated-at.bofh.it>
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On (04/27/17 12:14), Steven Rostedt wrote:
[..]
> I tried this patch. It's better because I get the end of the trace, but
> I do lose the beginning of it:
> 
> ** 196358 printk messages dropped ** [  102.321182]     perf-5981    0.... 12983650us : d_path <-seq_path

many thanks!

so we now drop messages from logbuf, not from per-CPU buffers. that
"queue printk_deferred irq_work on every online CPU when we bypass per-CPU
buffers from NMI" idea *probably* might help here - we need someone to emit
messages from the logbuf while we printk from NMI. there is still a
possibility that we can drop messages, though, since log_store() from NMI
CPU can be much-much faster than call_console_drivers() on other CPU.

	-ss

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Thread

Re: [PATCH v5 1/4] printk/nmi: generic solution for safe printk in  NMI Steven Rostedt <rostedt@goodmis.org> - 2017-04-27 18:20 +0200
  Re: [PATCH v5 1/4] printk/nmi: generic solution for safe printk in  NMI Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-04-28 03:40 +0200
    Re: [PATCH v5 1/4] printk/nmi: generic solution for safe printk in  NMI Petr Mladek <pmladek@suse.com> - 2017-04-28 15:00 +0200
      Re: [PATCH v5 1/4] printk/nmi: generic solution for safe printk in  NMI Steven Rostedt <rostedt@goodmis.org> - 2017-04-28 16:20 +0200

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