Re: [RFC][PATCHv4 0/7] printk: introduce printing kernel threads

From	Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Newsgroups	linux.kernel
Subject	Re: [RFC][PATCHv4 0/7] printk: introduce printing kernel threads
Date	2017-06-30 14:50 +0200
Message-ID	<tY3x0-5xi-5@gated-at.bofh.it> (permalink)
References	<tNQKJ-7rJ-7@gated-at.bofh.it> <tQ0PE-1Le-23@gated-at.bofh.it> <tXlvX-7r0-3@gated-at.bofh.it> <tXCwO-4ON-17@gated-at.bofh.it> <tY33Y-5nU-19@gated-at.bofh.it>
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On (06/30/17 14:11), Petr Mladek wrote:
> > 2) can offload printing to other CPUs from vprintk_emit()
> >    and avoid any of scheduler->timekeeping->etc. paths. which will
> >    replace printk_deferred().
> 
> I probably miss something. There is still called wake_up_process()
> in this patchset and we could not do this in some scheduler and
> timekeeping paths. Also we must not take the console_lock() in
> these paths because it calls wake_up_process() as well. But
> we want to flush few lines when possible.

yes. but we could call wake_up_process() on !this_cpu.
so we wouldn't take this_cpu ->rq lock and so on.

	CPU1

	vprintk_emit()
		wake_up_process(printk_kthread on CPU2);

	-ss

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Re: [RFC][PATCHv4 0/7] printk: introduce printing kernel threads Petr Mladek <pmladek@suse.com> - 2017-06-28 15:50 +0200
  Re: [RFC][PATCHv4 0/7] printk: introduce printing kernel threads Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-06-29 10:00 +0200
    Re: [RFC][PATCHv4 0/7] printk: introduce printing kernel threads Petr Mladek <pmladek@suse.com> - 2017-06-30 14:20 +0200
      Re: [RFC][PATCHv4 0/7] printk: introduce printing kernel threads Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-06-30 14:50 +0200

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