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Re: [Query] Preemption (hogging) of the work handler

From Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Newsgroups linux.kernel
Subject Re: [Query] Preemption (hogging) of the work handler
Date 2016-07-15 15:20 +0200
Message-ID <rVbc5-7mF-3@gated-at.bofh.it> (permalink)
References (5 earlier) <rTS1P-4LO-17@gated-at.bofh.it> <rU2kx-32M-11@gated-at.bofh.it> <rU5s5-51i-3@gated-at.bofh.it> <rU6xQ-5Z5-31@gated-at.bofh.it> <rUYHU-7Ps-27@gated-at.bofh.it>
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Hello,

On (07/14/16 16:52), Viresh Kumar wrote:
> On 12-07-16, 23:03, Sergey Senozhatsky wrote:
> > so, I'm looking at this thing now:
> > 
> > : [   12.874909] sched: RT throttling activated for rt_rq ffffffc0ac13fcd0 (cpu 0)
> > : [   12.874909] potential CPU hogs:
> > : [   12.874909]  printk (292)
> > 
[..]
> - But before that it dumps the kernel-messages from last boot and the prints
>   looked like this:

kmsg_dump()? a wild guess... any chance that you kmsg dumper iterates
log_buf records under logbuf_lock long enough to cause throttling on
other CPU, because printk_kthread is simply has to spin on logbuf_lock?

something like

CPU0						CPU1

console_unlock()				kmsg_dump()
{						{
							kmsg_dump_get_buffer()
							{
								spin_lock(&logbuf_lock)

	spin_lock(&logbuf_lock)					while (....) {
							 	^^^^^^^^^^^^^^ long enough
									...
								}
								spin_unlock(&logbuf_lock)
							}
	....					}
	spin_unlock(&logbuf_lock)

	call_console_drivers()

	cond_resched()
		RT throttling
			printk_deferred("RT throttling")
}

	-ss


>   [   12.805180] [    7.919623] **Some Kernel Messages here**
> 
> Double time-stamp here, because one was already present in the last KMSG (logs
> from previous boot).
> 
> After around 100 lines got printed, we had this throttling messages (without the
> double timestamp), and we continue to print things after it as well.
> 
> -- 
> viresh
> 

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Thread

Re: [Query] Preemption (hogging) of the work handler Jan Kara <jack@suse.cz> - 2016-07-11 12:30 +0200
  Re: [Query] Preemption (hogging) of the work handler Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2016-07-11 17:50 +0200
    Re: [Query] Preemption (hogging) of the work handler "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2016-07-12 00:40 +0200
      Re: [Query] Preemption (hogging) of the work handler Viresh Kumar <viresh.kumar@linaro.org> - 2016-07-12 00:50 +0200
        Re: [Query] Preemption (hogging) of the work handler "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2016-07-12 14:30 +0200
          Re: [Query] Preemption (hogging) of the work handler Viresh Kumar <viresh.kumar@linaro.org> - 2016-07-12 15:10 +0200
            Re: [Query] Preemption (hogging) of the work handler Petr Mladek <pmladek@suse.com> - 2016-07-12 16:00 +0200
              Re: [Query] Preemption (hogging) of the work handler Viresh Kumar <viresh.kumar@linaro.org> - 2016-07-12 16:10 +0200
    Re: [Query] Preemption (hogging) of the work handler Viresh Kumar <viresh.kumar@linaro.org> - 2016-07-12 00:40 +0200
      Re: [Query] Preemption (hogging) of the work handler Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-07-12 11:40 +0200
        Re: [Query] Preemption (hogging) of the work handler Petr Mladek <pmladek@suse.com> - 2016-07-12 15:00 +0200
          Re: [Query] Preemption (hogging) of the work handler Viresh Kumar <viresh.kumar@linaro.org> - 2016-07-12 15:20 +0200
            Re: [Query] Preemption (hogging) of the work handler Viresh Kumar <viresh.kumar@linaro.org> - 2016-07-12 19:20 +0200
              Re: [Query] Preemption (hogging) of the work handler Viresh Kumar <viresh.kumar@linaro.org> - 2016-07-12 22:10 +0200
              Re: [Query] Preemption (hogging) of the work handler "Rafael J. Wysocki" <rafael@kernel.org> - 2016-07-12 22:10 +0200
              Re: [Query] Preemption (hogging) of the work handler Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-07-13 09:10 +0200
                Re: [Query] Preemption (hogging) of the work handler "Rafael J. Wysocki" <rafael@kernel.org> - 2016-07-13 14:10 +0200
                Re: [Query] Preemption (hogging) of the work handler Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2016-07-13 15:00 +0200
                Re: [Query] Preemption (hogging) of the work handler "Rafael J. Wysocki" <rafael@kernel.org> - 2016-07-13 15:30 +0200
          Re: [Query] Preemption (hogging) of the work handler Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2016-07-12 16:10 +0200
            Re: [Query] Preemption (hogging) of the work handler Viresh Kumar <viresh.kumar@linaro.org> - 2016-07-15 02:00 +0200
              Re: [Query] Preemption (hogging) of the work handler Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2016-07-15 15:20 +0200
                Re: [Query] Preemption (hogging) of the work handler Viresh Kumar <viresh.kumar@linaro.org> - 2016-07-15 18:00 +0200
      Re: [Query] Preemption (hogging) of the work handler Viresh Kumar <viresh.kumar@linaro.org> - 2016-07-13 01:30 +0200
        Re: [Query] Preemption (hogging) of the work handler Viresh Kumar <viresh.kumar@linaro.org> - 2016-07-13 02:20 +0200
        Re: [Query] Preemption (hogging) of the work handler Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-07-13 07:50 +0200
          Re: [Query] Preemption (hogging) of the work handler Viresh Kumar <viresh.kumar@linaro.org> - 2016-07-13 17:50 +0200
            Re: [Query] Preemption (hogging) of the work handler "Rafael J. Wysocki" <rafael@kernel.org> - 2016-07-14 01:10 +0200
              Re: [Query] Preemption (hogging) of the work handler Viresh Kumar <viresh.kumar@linaro.org> - 2016-07-14 01:20 +0200
                Re: [Query] Preemption (hogging) of the work handler Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-14 01:40 +0200
            Re: [Query] Preemption (hogging) of the work handler Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-07-14 03:00 +0200
              Re: [Query] Preemption (hogging) of the work handler "Rafael J. Wysocki" <rafael@kernel.org> - 2016-07-14 03:10 +0200
                Re: [Query] Preemption (hogging) of the work handler Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2016-07-14 03:40 +0200
                Re: [Query] Preemption (hogging) of the work handler Viresh Kumar <viresh.kumar@linaro.org> - 2016-07-15 00:00 +0200
              Re: [Query] Preemption (hogging) of the work handler Viresh Kumar <viresh.kumar@linaro.org> - 2016-07-15 00:00 +0200
          Re: [Query] Preemption (hogging) of the work handler Jan Kara <jack@suse.cz> - 2016-07-14 16:20 +0200
            Re: [Query] Preemption (hogging) of the work handler "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2016-07-14 16:30 +0200
              Re: [Query] Preemption (hogging) of the work handler Jan Kara <jack@suse.cz> - 2016-07-14 16:40 +0200
                Re: [Query] Preemption (hogging) of the work handler "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2016-07-14 16:50 +0200
                Re: [Query] Preemption (hogging) of the work handler Jan Kara <jack@suse.cz> - 2016-07-14 17:00 +0200
                Re: [Query] Preemption (hogging) of the work handler Viresh Kumar <viresh.kumar@linaro.org> - 2016-07-15 00:20 +0200
            Re: [Query] Preemption (hogging) of the work handler Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2016-07-14 16:40 +0200
              Re: [Query] Preemption (hogging) of the work handler Jan Kara <jack@suse.cz> - 2016-07-14 17:10 +0200
            Re: [Query] Preemption (hogging) of the work handler Viresh Kumar <viresh.kumar@linaro.org> - 2016-07-15 00:20 +0200
              Re: [Query] Preemption (hogging) of the work handler Jan Kara <jack@suse.cz> - 2016-07-18 13:10 +0200
                Re: [Query] Preemption (hogging) of the work handler "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2016-07-18 13:50 +0200
  Re: [Query] Preemption (hogging) of the work handler Viresh Kumar <viresh.kumar@linaro.org> - 2016-07-11 21:10 +0200

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