linux-kernel - Re: [RFC PATCH v2] membarrier: expedited private command

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Message-ID: <20170729105154.GD6524@worktop.programming.kicks-ass.net>
Date:   Sat, 29 Jul 2017 12:51:54 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Nicholas Piggin <npiggin@...il.com>
Cc:     Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Boqun Feng <boqun.feng@...il.com>,
        Andrew Hunter <ahh@...gle.com>,
        maged michael <maged.michael@...il.com>,
        gromer <gromer@...gle.com>, Avi Kivity <avi@...lladb.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Palmer Dabbelt <palmer@...belt.com>
Subject: Re: [RFC PATCH v2] membarrier: expedited private command

On Sat, Jul 29, 2017 at 07:48:56PM +1000, Nicholas Piggin wrote:
> On Sat, 29 Jul 2017 19:45:43 +1000
> Nicholas Piggin <npiggin@...il.com> wrote:
> 
> > hmm, we might be able to restrict iteration
> > to mm_cpumask(current->mm), no? 
> 
> Oh that's been discussed too. I'll read back over it too.

Right, the main problem is that some architectures (arm64 for instance,
although Will is looking at it) don't use mm_cpumask() at all.

Other architectures (PPC for instance) only ever set bits.