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Re: Regression in next with use printk_safe buffers in printk

From Peter Zijlstra <peterz@infradead.org>
Newsgroups linux.kernel
Subject Re: Regression in next with use printk_safe buffers in printk
Date 2017-02-14 17:20 +0100
Message-ID <taNZD-44x-5@gated-at.bofh.it> (permalink)
References <tauaC-7Oj-15@gated-at.bofh.it> <taNPX-41e-7@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On Wed, Feb 15, 2017 at 01:01:40AM +0900, Sergey Senozhatsky wrote:
> 
> but I'm a bit confused by rt_b->rt_runtime_lock in this unsafe lock
> scenario (so it's not ABBA, but ABAD)
> 
> >   lock(hrtimer_bases.lock);
> >                                lock(&rt_b->rt_runtime_lock);
> >                                lock(hrtimer_bases.lock);
> >   lock(tk_core);
> >
> >
> > Chain exists of:
> >
> >	tk_core --> &rt_b->rt_runtime_lock --> hrtimer_bases.lock
> 
> 
> I'm lacking some knowledge here, sorry. where does the tk_core --> &rt_b->rt_runtime_lock
> come from?

rt_b->rt_runtime_lock is one of the scheduler locks, since we do
printk() under tk_core, which does semaphore muck, which then includes
the entire scheduler chain of locks.

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Thread

Regression in next with use printk_safe buffers in printk Tony Lindgren <tony@atomide.com> - 2017-02-13 20:10 +0100
  Re: Regression in next with use printk_safe buffers in printk Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2017-02-14 17:10 +0100
    Re: Regression in next with use printk_safe buffers in printk Peter Zijlstra <peterz@infradead.org> - 2017-02-14 17:20 +0100
      Re: Regression in next with use printk_safe buffers in printk Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2017-02-14 18:00 +0100
        Re: Regression in next with use printk_safe buffers in printk Tony Lindgren <tony@atomide.com> - 2017-02-14 18:10 +0100
          Re: Regression in next with use printk_safe buffers in printk Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-02-15 05:50 +0100
        Re: Regression in next with use printk_safe buffers in printk Peter Zijlstra <peterz@infradead.org> - 2017-02-14 19:40 +0100
          Re: Regression in next with use printk_safe buffers in printk Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-02-15 05:50 +0100
    Re: Regression in next with use printk_safe buffers in printk Tony Lindgren <tony@atomide.com> - 2017-02-14 18:00 +0100
    Re: Regression in next with use printk_safe buffers in printk Tony Lindgren <tony@atomide.com> - 2017-02-15 19:10 +0100
      Re: Regression in next with use printk_safe buffers in printk Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-02-16 02:40 +0100
        Re: Regression in next with use printk_safe buffers in printk Tony Lindgren <tony@atomide.com> - 2017-02-16 05:10 +0100
          Re: Regression in next with use printk_safe buffers in printk Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-02-16 05:30 +0100
            Re: Regression in next with use printk_safe buffers in printk Tony Lindgren <tony@atomide.com> - 2017-02-16 16:20 +0100
              Re: Regression in next with use printk_safe buffers in printk Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2017-02-16 17:40 +0100
                Re: Regression in next with use printk_safe buffers in printk Tony Lindgren <tony@atomide.com> - 2017-02-16 20:20 +0100

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