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From: Juri Lelli <juri.lelli@arm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: mingo@kernel.org, tglx@linutronix.de, rostedt@goodmis.org,
	xlpang@redhat.com, linux-kernel@vger.kernel.org,
	mathieu.desnoyers@efficios.com, jdesfossez@efficios.com,
	bristot@redhat.com
Subject: Re: [RFC][PATCH 8/8] rtmutex: Fix PI chain order integrity
Date: Tue, 28 Jun 2016 10:05:53 +0100	[thread overview]
Message-ID: <20160628090553.GO5981@e106622-lin> (raw)
In-Reply-To: <20160627122335.GB30154@twins.programming.kicks-ass.net>

On 27/06/16 14:23, Peter Zijlstra wrote:
> On Wed, Jun 15, 2016 at 08:25:07AM +0100, Juri Lelli wrote:
> > I guess it's not that likely, but yes it could potentially happen that a
> > waiter is optimistically spinning, depletes its runtime, gets throttled
> > and then replenished when still spinning. Maybe it doesn't really make
> > sense continuing spinning in this situation, but I guess things get
> > really complicated. :-/
> > 
> > Anyway, as said, I think this patch is OK. Maybe we want to add a
> > comment just to remember what situation can cause an issue if we don't
> > do this? Patch changelog would be OK as well for such a comment IMHO.
> 
> 
> OK, so I went to write a simple comment and ended up with the below :/
> 
> While writing the comment I noticed two issues:
> 
>  - we update the waiter order fields while the entry is still enqueued
>    on the pi_waiters tree, which is also sorted by these exact fields.
> 
>  - another one of these pure ->prio comparisons
> 
> Please double check, there be dragons here.
> 

Reviewed-and-tested-by: Juri Lelli <juri.lelli@arm.com>

And, FWIW, you can obviously keep this if you are going to squash this
into 8/8.

Best,

- Juri

      parent reply	other threads:[~2016-06-28  9:05 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-07 19:56 [RFC][PATCH 0/8] PI and assorted failings Peter Zijlstra
2016-06-07 19:56 ` [RFC][PATCH 1/8] rtmutex: Deboost before waking up the top waiter Peter Zijlstra
2016-06-14  9:09   ` Juri Lelli
2016-06-14 12:54     ` Peter Zijlstra
2016-06-14 13:20       ` Juri Lelli
2016-06-14 13:59         ` Peter Zijlstra
2016-06-14 16:36     ` Davidlohr Bueso
2016-06-14 17:01       ` Juri Lelli
2016-06-14 18:22   ` Steven Rostedt
2016-06-07 19:56 ` [RFC][PATCH 2/8] sched/rtmutex/deadline: Fix a PI crash for deadline tasks Peter Zijlstra
2016-06-14 10:21   ` Juri Lelli
2016-06-14 12:30     ` Peter Zijlstra
2016-06-14 12:53     ` Xunlei Pang
2016-06-14 13:07       ` Juri Lelli
2016-06-14 16:39         ` Juri Lelli
2016-06-14 18:42   ` Steven Rostedt
2016-06-14 20:28     ` Peter Zijlstra
2016-06-15 16:14       ` Steven Rostedt
2016-06-07 19:56 ` [RFC][PATCH 3/8] sched/deadline/rtmutex: Dont miss the dl_runtime/dl_period update Peter Zijlstra
2016-06-14 10:43   ` Juri Lelli
2016-06-14 12:09     ` Peter Zijlstra
2016-06-15 16:30   ` Steven Rostedt
2016-06-15 17:55     ` Peter Zijlstra
2016-06-07 19:56 ` [RFC][PATCH 4/8] rtmutex: Remove rt_mutex_fastunlock() Peter Zijlstra
2016-06-15 16:43   ` Steven Rostedt
2016-06-07 19:56 ` [RFC][PATCH 5/8] rtmutex: Clean up Peter Zijlstra
2016-06-14 12:08   ` Juri Lelli
2016-06-14 12:32     ` Peter Zijlstra
2016-06-14 12:41       ` Juri Lelli
2016-06-07 19:56 ` [RFC][PATCH 6/8] sched/rtmutex: Refactor rt_mutex_setprio() Peter Zijlstra
2016-06-14 13:14   ` Juri Lelli
2016-06-14 14:08     ` Peter Zijlstra
2016-06-07 19:56 ` [RFC][PATCH 7/8] sched,tracing: Update trace_sched_pi_setprio() Peter Zijlstra
2016-06-07 19:56 ` [RFC][PATCH 8/8] rtmutex: Fix PI chain order integrity Peter Zijlstra
2016-06-14 17:39   ` Juri Lelli
2016-06-14 19:44     ` Peter Zijlstra
2016-06-15  7:25       ` Juri Lelli
2016-06-27 12:23         ` Peter Zijlstra
2016-06-27 12:40           ` Thomas Gleixner
2016-06-28  9:05           ` Juri Lelli [this message]

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