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From: Darren Hart <dvhart@infradead.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: tglx@linutronix.de, mingo@kernel.org, juri.lelli@arm.com,
	rostedt@goodmis.org, xlpang@redhat.com, bigeasy@linutronix.de,
	linux-kernel@vger.kernel.org, mathieu.desnoyers@efficios.com,
	jdesfossez@efficios.com, bristot@redhat.com
Subject: Re: [PATCH -v6 12/13] futex: futex_unlock_pi() determinism
Date: Fri, 7 Apr 2017 18:27:07 -0700	[thread overview]
Message-ID: <20170408012707.GB16143@fury> (raw)
In-Reply-To: <20170322104152.112378812@infradead.org>

On Wed, Mar 22, 2017 at 11:35:59AM +0100, Peter Zijlstra wrote:
> The problem with returning -EAGAIN when the waiter state mismatches is
> that it becomes very hard to proof a bounded execution time on the

prove

> operation. And seeing that this is a RT operation, this is somewhat

an RT

> important.
> 
> While in practise; given the previous patch; it will be very unlikely

Heh, that's not what semicolons are for ;-) Commas here, or a parenthetical.

> to ever really take more than one or two rounds, proving so becomes
> rather hard.
> 
> However, now that modifying wait_list is done while holding both
> hb->lock and wait_lock, we can avoid the scenario entirely if we
> acquire wait_lock while still holding hb-lock. Doing a hand-over,
> without leaving a hole.

Nice :)

-- 
Darren Hart
VMware Open Source Technology Center

  parent reply	other threads:[~2017-04-08  1:27 UTC|newest]

Thread overview: 60+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-03-22 10:35 [PATCH -v6 00/13] The arduous story of FUTEX_UNLOCK_PI Peter Zijlstra
2017-03-22 10:35 ` [PATCH -v6 01/13] futex: Cleanup variable names for futex_top_waiter() Peter Zijlstra
2017-03-23 18:19   ` [tip:locking/core] " tip-bot for Peter Zijlstra
2017-03-24 21:11   ` [PATCH -v6 01/13] " Darren Hart
2017-03-22 10:35 ` [PATCH -v6 02/13] futex: Use smp_store_release() in mark_wake_futex() Peter Zijlstra
2017-03-23 18:19   ` [tip:locking/core] " tip-bot for Peter Zijlstra
2017-03-24 21:16   ` [PATCH -v6 02/13] " Darren Hart
2017-03-22 10:35 ` [PATCH -v6 03/13] futex: Remove rt_mutex_deadlock_account_*() Peter Zijlstra
2017-03-23 18:20   ` [tip:locking/core] " tip-bot for Peter Zijlstra
2017-03-24 21:29   ` [PATCH -v6 03/13] " Darren Hart
2017-03-24 21:31     ` Darren Hart
2017-03-22 10:35 ` [PATCH -v6 04/13] futex,rt_mutex: Provide futex specific rt_mutex API Peter Zijlstra
2017-03-23 18:20   ` [tip:locking/core] " tip-bot for Peter Zijlstra
2017-03-25  0:37   ` [PATCH -v6 04/13] " Darren Hart
2017-04-06 12:15     ` Peter Zijlstra
2017-04-06 17:02       ` Darren Hart
2017-04-05 15:02   ` Darren Hart
2017-04-06 12:17     ` Peter Zijlstra
2017-04-06 17:08       ` Darren Hart
2017-03-22 10:35 ` [PATCH -v6 05/13] futex: Change locking rules Peter Zijlstra
2017-03-23 18:21   ` [tip:locking/core] " tip-bot for Peter Zijlstra
2017-04-05 21:18   ` [PATCH -v6 05/13] " Darren Hart
2017-04-06 12:28     ` Peter Zijlstra
2017-04-06 15:58       ` Joe Perches
2017-04-06 17:21       ` Darren Hart
2017-03-22 10:35 ` [PATCH -v6 06/13] futex: Cleanup refcounting Peter Zijlstra
2017-03-23 18:21   ` [tip:locking/core] " tip-bot for Peter Zijlstra
2017-04-05 21:29   ` [PATCH -v6 06/13] " Darren Hart
2017-03-22 10:35 ` [PATCH -v6 07/13] futex: Rework inconsistent rt_mutex/futex_q state Peter Zijlstra
2017-03-23 18:22   ` [tip:locking/core] " tip-bot for Peter Zijlstra
2017-04-05 21:58   ` [PATCH -v6 07/13] " Darren Hart
2017-03-22 10:35 ` [PATCH -v6 08/13] futex: Pull rt_mutex_futex_unlock() out from under hb->lock Peter Zijlstra
2017-03-23 18:22   ` [tip:locking/core] " tip-bot for Peter Zijlstra
2017-04-05 23:52   ` [PATCH -v6 08/13] " Darren Hart
2017-04-06 12:42     ` Peter Zijlstra
2017-04-06 17:42       ` Darren Hart
2017-03-22 10:35 ` [PATCH -v6 09/13] futex,rt_mutex: Introduce rt_mutex_init_waiter() Peter Zijlstra
2017-03-23 18:23   ` [tip:locking/core] " tip-bot for Peter Zijlstra
2017-04-05 23:57   ` [PATCH -v6 09/13] " Darren Hart
2017-03-22 10:35 ` [PATCH -v6 10/13] futex,rt_mutex: Restructure rt_mutex_finish_proxy_lock() Peter Zijlstra
2017-03-23 18:23   ` [tip:locking/core] " tip-bot for Peter Zijlstra
2017-04-07 23:30   ` [PATCH -v6 10/13] " Darren Hart
2017-04-07 23:35     ` Darren Hart
2017-03-22 10:35 ` [PATCH -v6 11/13] futex: Rework futex_lock_pi() to use rt_mutex_*_proxy_lock() Peter Zijlstra
2017-03-23 18:24   ` [tip:locking/core] " tip-bot for Peter Zijlstra
2017-04-08  0:55   ` [PATCH -v6 11/13] " Darren Hart
2017-04-10 15:51   ` alexander.levin
2017-04-10 16:03     ` Thomas Gleixner
2017-04-14  9:30       ` [tip:locking/core] futex: Avoid freeing an active timer tip-bot for Thomas Gleixner
2017-03-22 10:35 ` [PATCH -v6 12/13] futex: futex_unlock_pi() determinism Peter Zijlstra
2017-03-23 18:24   ` [tip:locking/core] futex: Futex_unlock_pi() determinism tip-bot for Peter Zijlstra
2017-04-08  1:27   ` Darren Hart [this message]
2017-03-22 10:36 ` [PATCH -v6 13/13] futex: futex_lock_pi() vs PREEMPT_RT_FULL Peter Zijlstra
2017-03-23 18:25   ` [tip:locking/core] futex: Drop hb->lock before enqueueing on the rtmutex tip-bot for Peter Zijlstra
2017-04-08  2:26   ` [PATCH -v6 13/13] futex: futex_lock_pi() vs PREEMPT_RT_FULL Darren Hart
2017-04-08  5:22     ` Mike Galbraith
2017-04-10  8:43     ` Sebastian Andrzej Siewior
2017-04-10  9:08     ` Peter Zijlstra
2017-04-10 16:05       ` Darren Hart
2017-03-24  1:45 ` [PATCH -v6 00/13] The arduous story of FUTEX_UNLOCK_PI Darren Hart

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