From: Peter Zijlstra <peterz@infradead.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: xlpang@redhat.com, linux-kernel@vger.kernel.org,
Juri Lelli <juri.lelli@arm.com>, Ingo Molnar <mingo@redhat.com>,
Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH v3 1/6] rtmutex: Deboost before waking up the top waiter
Date: Wed, 20 Apr 2016 15:10:54 +0200 [thread overview]
Message-ID: <20160420131054.GA3430@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <alpine.DEB.2.11.1604201427520.3941@nanos>
On Wed, Apr 20, 2016 at 02:43:29PM +0200, Thomas Gleixner wrote:
> > So its semantically icky to have the two tasks running off the same
> > state and practically icky when you consider bandwidth inheritance --
> > where the boosted task wants to explicitly modify the state of the
> > booster.
> >
> > In that latter case you really want to unboost before you let the
> > booster run again.
>
> I understand that. That doesn't make the changelog any better, which mumbles
> about priorities :(
Agreed.
> > However, you noted we need to deal with this case due to the whole
> > optimistic spinning crap anyway :/
>
> Right, but that's another dimension of madness. Both tasks are on a cpu.
> The reason why we boost the lock holder before spinning is to make
> sure that it does not get preempted by something of medium priority
> before dropping the lock.
Right; I figured that out pretty quickly, which is why this patch does a
preempt_disable() over the unboost+wakeup.
FWIW, the immediate reason for this patch is that is ensures the new
p->pi_task pointer, points to something that exists.
> That really gets interesting with bandwith inheritance ....
I'm more worried about the optimistic spinning case..
next prev parent reply other threads:[~2016-04-20 13:11 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-14 11:37 [PATCH v3 0/6] sched/deadline/rtmutex: Fix two deadline PI issues Xunlei Pang
2016-04-14 11:37 ` [PATCH v3 1/6] rtmutex: Deboost before waking up the top waiter Xunlei Pang
2016-04-18 8:23 ` Thomas Gleixner
2016-04-18 8:44 ` Xunlei Pang
2016-04-18 9:02 ` Thomas Gleixner
2016-04-18 9:41 ` Xunlei Pang
2016-04-20 12:20 ` Peter Zijlstra
2016-04-20 12:43 ` Thomas Gleixner
2016-04-20 13:10 ` Peter Zijlstra [this message]
2016-04-14 11:37 ` [PATCH v3 2/6] sched/rtmutex/deadline: Fix a PI crash for deadline tasks Xunlei Pang
2016-04-20 13:19 ` Peter Zijlstra
2016-04-20 13:49 ` Xunlei Pang
2016-04-22 3:26 ` Xunlei Pang
2016-04-14 11:37 ` [PATCH v3 3/6] rtmutex: Move "rt_mutex_waiter" definition to "include/linux/rtmutex.h" Xunlei Pang
2016-04-14 11:37 ` [PATCH v3 4/6] sched: Move dl_policy() to "include/linux/sched.h" Xunlei Pang
2016-04-14 11:37 ` [PATCH v3 5/6] sched/deadline/rtmutex: Fix unprotected PI access in enqueue_task_dl() Xunlei Pang
2016-04-14 15:31 ` Peter Zijlstra
2016-04-15 1:58 ` Xunlei Pang
2016-04-15 2:19 ` Xunlei Pang
2016-04-20 12:25 ` Peter Zijlstra
2016-04-20 13:00 ` Xunlei Pang
2016-04-20 13:17 ` Peter Zijlstra
2016-04-20 13:45 ` Xunlei Pang
2016-04-14 11:37 ` [PATCH v3 6/6] sched/deadline/rtmutex: Don't miss the dl_runtime/dl_period update Xunlei Pang
2017-03-23 14:56 [PATCH -v3 0/8] PI vs SCHED_DEADLINE fixes Peter Zijlstra
2017-03-23 14:56 ` [PATCH -v3 1/8] rtmutex: Deboost before waking up the top waiter Peter Zijlstra
2017-04-04 9:48 ` [tip:locking/core] " tip-bot for Xunlei Pang
2017-04-05 8:08 ` Mike Galbraith
2017-04-05 14:55 ` [tip:locking/core] Retiplockingcore_rtmutex_Deboost_before_waking_up_the_top_waiter tip-bot for Mike Galbraith
2017-04-05 15:03 ` [tip:locking/core] rtmutex: Plug preempt count leak in rt_mutex_futex_unlock() tip-bot for Mike Galbraith
2017-04-06 6:16 ` [tip:locking/core] rtmutex: Deboost before waking up the top waiter Xunlei Pang
2017-03-23 14:56 ` [PATCH -v3 2/8] sched/rtmutex/deadline: Fix a PI crash for deadline tasks Peter Zijlstra
2017-04-04 9:49 ` [tip:locking/core] " tip-bot for Xunlei Pang
2017-03-23 14:56 ` [PATCH -v3 3/8] sched/deadline/rtmutex: Dont miss the dl_runtime/dl_period update Peter Zijlstra
2017-04-04 9:50 ` [tip:locking/core] " tip-bot for Xunlei Pang
2017-03-23 14:56 ` [PATCH -v3 4/8] rtmutex: Clean up Peter Zijlstra
2017-03-23 18:21 ` Steven Rostedt
2017-04-04 9:50 ` [tip:locking/core] " tip-bot for Peter Zijlstra
2017-03-23 14:56 ` [PATCH -v3 5/8] sched/rtmutex: Refactor rt_mutex_setprio() Peter Zijlstra
2017-04-04 9:51 ` [tip:locking/core] " tip-bot for Peter Zijlstra
2017-03-23 14:56 ` [PATCH -v3 6/8] sched,tracing: Update trace_sched_pi_setprio() Peter Zijlstra
2017-04-04 9:51 ` [tip:locking/core] " tip-bot for Peter Zijlstra
2017-03-23 14:56 ` [PATCH -v3 7/8] rtmutex: Fix PI chain order integrity Peter Zijlstra
2017-04-04 9:52 ` [tip:locking/core] " tip-bot for Peter Zijlstra
2017-03-23 14:56 ` [PATCH -v3 8/8] rtmutex: Fix more prio comparisons Peter Zijlstra
2017-04-04 9:52 ` [tip:locking/core] " tip-bot for Peter Zijlstra
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