From: Peter Zijlstra <peterz@infradead.org>
To: Waiman Long <waiman.long@hp.com>
Cc: Jason Low <jason.low2@hp.com>,
mingo@redhat.com, paulmck@linux.vnet.ibm.com,
torvalds@linux-foundation.org, tglx@linutronix.de,
linux-kernel@vger.kernel.org, riel@redhat.com,
akpm@linux-foundation.org, davidlohr@hp.com, hpa@zytor.com,
andi@firstfloor.org, aswin@hp.com, scott.norton@hp.com,
chegu_vinod@hp.com
Subject: Re: [RFC][PATCH v2 5/5] mutex: Give spinners a chance to spin_on_owner if need_resched() triggered while queued
Date: Thu, 6 Feb 2014 15:04:35 +0100 [thread overview]
Message-ID: <20140206140435.GU8874@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <52F2B0C2.8040408@hp.com>
On Wed, Feb 05, 2014 at 04:44:34PM -0500, Waiman Long wrote:
> I have an alternative way of breaking out of the MCS lock waiting queue when
> need_resched() is set. I overload the locked flag to indicate a skipped node
> if negative.
I'm not quite seeing how it works (then again, I've not really read the
patch carefully).
Suppose you break out; at that point you get queued and go to sleep.
Suppose you got woken up while you MCS entry is still 'pending' and
magically win the race and acquire the lock.
At that point your MCS entry can be re-used while its still part of the
list.
Its a fantastically small race window, but I don't see anything that
makes it impossible.
> I run the patch through the AIM7 high-systime workload on a
> 4-socket server and it seemed to run fine.
How do people run this AIM7 piece of shit? I let it run for over an hour
and it generated exactly 0 numbers, it just sits there eating cpu-time
and creating a racket from my pantry.
next prev parent reply other threads:[~2014-02-06 14:04 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-28 19:13 [PATCH v2 0/5] mutex: Mutex scalability patches Jason Low
2014-01-28 19:13 ` [PATCH v2 1/5] mutex: In mutex_can_spin_on_owner(), return false if task need_resched() Jason Low
2014-01-28 20:20 ` Paul E. McKenney
2014-01-28 22:01 ` Jason Low
2014-01-28 21:09 ` Davidlohr Bueso
2014-03-11 12:41 ` [tip:core/locking] locking/mutexes: Return false if task need_resched() in mutex_can_spin_on_owner() tip-bot for Jason Low
2014-01-28 19:13 ` [PATCH v2 2/5] mutex: Modify the way optimistic spinners are queued Jason Low
2014-01-28 20:23 ` Paul E. McKenney
2014-01-28 20:24 ` Paul E. McKenney
2014-01-28 21:17 ` Davidlohr Bueso
2014-01-28 22:10 ` Jason Low
2014-02-02 21:58 ` Paul E. McKenney
2014-03-11 12:41 ` [tip:core/locking] locking/mutexes: " tip-bot for Jason Low
2014-03-11 15:24 ` Jason Low
2014-03-11 15:33 ` Peter Zijlstra
2014-01-28 19:13 ` [PATCH v2 3/5] mutex: Unlock the mutex without the wait_lock Jason Low
2014-03-11 12:41 ` [tip:core/locking] locking/mutexes: " tip-bot for Jason Low
2014-03-12 12:24 ` Peter Zijlstra
2014-03-12 18:44 ` Jason Low
2014-03-13 7:28 ` [tip:core/locking] locking/mutex: Fix debug checks tip-bot for Peter Zijlstra
2014-01-28 19:13 ` [RFC][PATCH v2 4/5] mutex: Disable preemtion between modifying lock->owner and locking/unlocking mutex Jason Low
2014-01-28 20:54 ` Peter Zijlstra
2014-01-28 22:17 ` Jason Low
2014-01-28 19:13 ` [RFC][PATCH v2 5/5] mutex: Give spinners a chance to spin_on_owner if need_resched() triggered while queued Jason Low
2014-01-28 21:07 ` Peter Zijlstra
2014-01-28 22:51 ` Jason Low
2014-01-29 11:51 ` Peter Zijlstra
2014-01-31 3:29 ` Jason Low
2014-01-31 14:09 ` Peter Zijlstra
2014-01-31 20:01 ` Jason Low
2014-01-31 20:08 ` Peter Zijlstra
2014-02-02 21:01 ` Jason Low
2014-02-02 21:12 ` Peter Zijlstra
2014-02-03 18:39 ` Jason Low
2014-02-03 19:25 ` Peter Zijlstra
2014-02-03 20:55 ` Jason Low
2014-02-03 21:06 ` Peter Zijlstra
2014-02-03 21:56 ` Jason Low
2014-02-04 7:13 ` Jason Low
2014-02-02 22:02 ` Paul E. McKenney
2014-02-02 20:02 ` Peter Zijlstra
2014-02-05 21:44 ` Waiman Long
2014-02-06 14:04 ` Peter Zijlstra [this message]
2014-02-06 18:45 ` Waiman Long
2014-02-06 20:10 ` Norton, Scott J
2014-02-10 17:01 ` Peter Zijlstra
2014-02-06 17:44 ` Jason Low
2014-02-06 18:37 ` Waiman Long
2014-01-28 21:08 ` [PATCH v2 0/5] mutex: Mutex scalability patches Davidlohr Bueso
2014-01-28 23:11 ` Jason Low
-- strict thread matches above, loose matches on Subject: below --
2014-02-06 14:52 [RFC][PATCH v2 5/5] mutex: Give spinners a chance to spin_on_owner if need_resched() triggered while queued Daniel J Blueman
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