Date: Fri, 8 Apr 2016 15:28:01 -0400
From: Steven Rostedt <rostedt@goodmis.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: xlpang@redhat.com, linux-kernel@vger.kernel.org,
        Juri Lelli <juri.lelli@arm.com>, Ingo Molnar <mingo@redhat.com>,
        Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH] sched/deadline/rtmutex: Fix a PI crash for deadline
 tasks
Message-ID: <20160408152801.3f0b1c33@gandalf.local.home>
In-Reply-To: <20160408151542.24328fd6@gandalf.local.home>
References: <56FE685E.6080001@redhat.com>
	<19912883-8AB1-4DFD-A0E1-F23057785243@infradead.org>
	<56FE78E0.5060504@redhat.com>
	<20160401215143.GB2906@worktop>
	<57037974.1020002@redhat.com>
	<20160405091954.GI3448@twins.programming.kicks-ass.net>
	<20160405092954.GC24771@twins.programming.kicks-ass.net>
	<20160408122510.15978179@gandalf.local.home>
	<20160408173835.GC1087@worktop>
	<20160408145055.13c98a75@gandalf.local.home>
	<20160408185916.GQ3448@twins.programming.kicks-ass.net>
	<20160408151542.24328fd6@gandalf.local.home>
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1068
Lines: 25

On Fri, 8 Apr 2016 15:15:42 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> From what I understand, the slowfn() modifies the task pi_list (or
> rbtree, as it is today). As this is an unlock, the task being woken
> (the next one to grab the lock) is removed from the previous task's pi
> list.
> 
> In rt_mutex_adjust_prio(current) I see it simply grabs current's
> pi_lock and calls __rt_mutex_adjust_prio(current). This calls
> rt_mutex_getprio(current) which returns current's normal prio if it
> doesn't have any pi waiters, or it looks at the top pi waiter on the
> tasks list and returns that. Which wouldn't be the task on wake_q,
> otherwise we wouldn't be deboosting in the first place.
> 

OK, I now see that the your previous patch is changing what I'm looking
at :-) This is what happens when you go away and try to catch up on
email and not read the emails by threads. I see the
rt_mutex_adjust_prio() is being changed.

I'll go back and look at your previous patch (as I looked at that while
traveling and didn't think too hard about it).

-- Steve