Re: [PATCH 2/3] rtmutex: deboost priority conditionally when rt-mutex unlock

From	Peter Zijlstra <peterz@infradead.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH 2/3] rtmutex: deboost priority conditionally when rt-mutex unlock
Date	2017-04-13 19:00 +0200
Message-ID	<tvQg9-5H7-3@gated-at.bofh.it> (permalink)
References	(1 earlier) <tvNBD-43N-1@gated-at.bofh.it> <tvOem-4jh-7@gated-at.bofh.it> <tvPDr-5oA-1@gated-at.bofh.it> <tvPN7-5sD-5@gated-at.bofh.it> <tvQ6u-5Bw-27@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Thu, Apr 13, 2017 at 12:40:14PM -0400, Steven Rostedt wrote:
> On Thu, 13 Apr 2017 18:21:13 +0200
> Peter Zijlstra <peterz@infradead.org> wrote:
> 
> > On Thu, Apr 13, 2017 at 12:09:25PM -0400, Steven Rostedt wrote:
> > > On Thu, 13 Apr 2017 16:39:52 +0200
> > > Peter Zijlstra <peterz@infradead.org> wrote:
> > >   
> > > > On Thu, Apr 13, 2017 at 10:02:53PM +0800, Alex Shi wrote:  
> > > > >  	/*
> > > > > +	 * 'current' release this lock, so 'current' should be a higher prio
> > > > > +	 * task than the next top waiter, unless the current prio was gotten
> > > > > +	 * from this top waiter, iff so, we need to deboost 'current' after
> > > > > +	 * the lock release.
> > > > > +	 */
> > > > > +	if (current->prio == waiter->prio)
> > > > > +		deboost = true;    
> > > > 
> > > > This is wrong.  
> > > 
> > > The comment is, especially that "iff". What if current and waiter
> > > happen to have the same priority? Then it too doesn't need to be
> > > deboosted.  
> > 
> > The wrongness is in comparing prio and thinking it means anything.
> 
> Because of deadline scheduling?

Yep.

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[PATCH 2/3] rtmutex: deboost priority conditionally when rt-mutex unlock Alex Shi <alex.shi@linaro.org> - 2017-04-13 16:10 +0200
  Re: [PATCH 2/3] rtmutex: deboost priority conditionally when  rt-mutex unlock Sebastian Siewior <bigeasy@linutronix.de> - 2017-04-13 16:30 +0200
  Re: [PATCH 2/3] rtmutex: deboost priority conditionally when  rt-mutex unlock Peter Zijlstra <peterz@infradead.org> - 2017-04-13 16:50 +0200
    Re: [PATCH 2/3] rtmutex: deboost priority conditionally when  rt-mutex unlock Steven Rostedt <rostedt@goodmis.org> - 2017-04-13 18:20 +0200
      Re: [PATCH 2/3] rtmutex: deboost priority conditionally when  rt-mutex unlock Peter Zijlstra <peterz@infradead.org> - 2017-04-13 18:30 +0200
        Re: [PATCH 2/3] rtmutex: deboost priority conditionally when  rt-mutex unlock Steven Rostedt <rostedt@goodmis.org> - 2017-04-13 18:50 +0200
          Re: [PATCH 2/3] rtmutex: deboost priority conditionally when  rt-mutex unlock Peter Zijlstra <peterz@infradead.org> - 2017-04-13 19:00 +0200

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