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, 14 Jun 2016 18:39:08 +0100 [thread overview]
Message-ID: <20160614173908.GQ5981@e106622-lin> (raw)
In-Reply-To: <20160607200216.117270606@infradead.org>
On 07/06/16 21:56, Peter Zijlstra wrote:
> rt_mutex_waiter::prio is a copy of task_struct::prio which is updated
> during the PI chain walk, such that the PI chain order isn't messed up
> by (asynchronous) task state updates.
>
> Currently rt_mutex_waiter_less() uses task state for deadline tasks;
> this is broken, since the task state can, as said above, change
> asynchronously, causing the RB tree order to change without actual
> tree update -> FAIL.
>
> Fix this by also copying the deadline into the rt_mutex_waiter state
> and updating it along with its prio field.
>
> Ideally we would also force PI chain updates whenever DL tasks update
> their deadline parameter, but for first approximation this is less
> broken than it was.
>
The patch looks OK to me. However, I'm failing to see when we can update
dl.deadline of a waiter asynchronously. Since a waiter is blocked, we
can't really change his dl.deadline by calling setscheduler on him, as
the update would operate on dl.dl_deadline. The new values will start to
be used as soon as it gets unblocked. The situation seems different for
RT tasks, for which priority change takes effect immediately.
What am I missing? :-)
next prev parent reply other threads:[~2016-06-14 17:39 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 [this message]
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
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