From: Peter Zijlstra <peterz@infradead.org>
To: Davidlohr Bueso <dave@stgolabs.net>
Cc: Ingo Molnar <mingo@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
linux-kernel@vger.kernel.org, Davidlohr Bueso <dbueso@suse.de>
Subject: Re: [PATCH -tip 2/3] sched/wake_q: Relax to acquire semantics
Date: Wed, 16 Sep 2015 11:01:52 +0200 [thread overview]
Message-ID: <20150916090152.GB3816@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20150915194945.GI19736@linux-q0g1.site>
On Tue, Sep 15, 2015 at 12:49:46PM -0700, Davidlohr Bueso wrote:
> On Tue, 15 Sep 2015, Peter Zijlstra wrote:
>
> >>Secondly, the wake queues are not concurrent, they're in context, so I
> >>don't see ordering matter at all. The only reason its a cmpxchg() is
> >>because there is the (small) possibility of two contexts wanting to wake
> >>the same task, and we use task_struct storage for the queue.
> >
> >I don't think we need _any_ barriers here, unless we have concurrent
> >users of the wake queues (or want to allow any, do we?).
>
> Exactly, the queues are not concurent and do not need barriers, but some of
> our callers do expect them.
Ah, that is what you were saying. In that case, I think we should remove
all our barriers and make them explicit in the callers where needed.
next prev parent reply other threads:[~2015-09-16 9:07 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-14 7:37 [PATCH -tip 1/3] locking/qrwlock: Rename ->lock to ->wait_lock Davidlohr Bueso
2015-09-14 7:37 ` [PATCH -tip 2/3] sched/wake_q: Relax to acquire semantics Davidlohr Bueso
2015-09-14 12:32 ` Peter Zijlstra
2015-09-14 21:08 ` Davidlohr Bueso
2015-09-15 9:49 ` Peter Zijlstra
2015-09-15 9:55 ` Peter Zijlstra
2015-09-15 12:41 ` Paul E. McKenney
2015-09-15 12:48 ` Peter Zijlstra
2015-09-15 14:09 ` Paul E. McKenney
2015-09-15 14:14 ` Peter Zijlstra
2015-09-15 15:34 ` Paul E. McKenney
2015-09-15 16:30 ` Peter Zijlstra
2015-09-15 17:09 ` Paul E. McKenney
2015-09-18 21:41 ` Paul E. McKenney
2015-09-21 9:22 ` Martin Schwidefsky
2015-09-22 10:27 ` Martin Schwidefsky
2015-09-22 12:23 ` Boqun Feng
2015-09-22 12:51 ` Martin Schwidefsky
2015-09-22 13:29 ` Boqun Feng
2015-09-22 14:33 ` Martin Schwidefsky
2015-09-22 15:28 ` Paul E. McKenney
2015-09-23 6:43 ` Martin Schwidefsky
2015-09-25 21:30 ` Paul E. McKenney
2015-09-15 19:49 ` Davidlohr Bueso
2015-09-16 9:01 ` Peter Zijlstra [this message]
2015-09-14 7:37 ` [PATCH -tip 3/3] locking/osq: Relax atomic semantics Davidlohr Bueso
2015-09-18 8:50 ` [tip:locking/core] " tip-bot for Davidlohr Bueso
2015-09-18 8:50 ` [tip:locking/core] locking/qrwlock: Rename ->lock to ->wait_lock tip-bot for Davidlohr Bueso
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