linux-kernel - Re: [PATCH for 4.16 08/10] membarrier: x86: Provide core serializing command (v3)

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Message-ID: <84882000.4019.1516135269345.JavaMail.zimbra@efficios.com>
Date:   Tue, 16 Jan 2018 20:41:09 +0000 (UTC)
From:   Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-api <linux-api@...r.kernel.org>,
        Andy Lutomirski <luto@...nel.org>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Andrew Hunter <ahh@...gle.com>,
        maged michael <maged.michael@...il.com>,
        Avi Kivity <avi@...lladb.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Dave Watson <davejwatson@...com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andrea Parri <parri.andrea@...il.com>,
        "Russell King, ARM Linux" <linux@...linux.org.uk>,
        Greg Hackmann <ghackmann@...gle.com>,
        Will Deacon <will.deacon@....com>,
        David Sehr <sehr@...gle.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        x86 <x86@...nel.org>, linux-arch <linux-arch@...r.kernel.org>
Subject: Re: [PATCH for 4.16 08/10] membarrier: x86: Provide core
 serializing command (v3)

----- On Jan 16, 2018, at 2:22 PM, Mathieu Desnoyers mathieu.desnoyers@...icios.com wrote:

> ----- On Jan 16, 2018, at 1:29 PM, Thomas Gleixner tglx@...utronix.de wrote:
> 
>> On Mon, 15 Jan 2018, Mathieu Desnoyers wrote:
>> 
>>> There are two places where core serialization is needed by membarrier:
>>> 
>>> 1) When returning from the membarrier IPI,
>>> 2) After scheduler updates curr to a thread with a different mm, before
>>>    going back to user-space, since the curr->mm is used by membarrier to
>>>    check whether it needs to send an IPI to that CPU.
>> 
>> This wants to be split into x86 and core changes. Ideally you make the core
>> changes before the previous patch and add the empty inline into
>> linux/processor.h....
> 
> Good point, done. The first commit introducing the new command now also
> introduces the generic stuff moved from the x86 patches.

Scratch this: it's cleaner if I add a separate generic patch to introduce
just the empty inline into linux/processor.h and the
ARCH_HAS_SYNC_CORE_BEFORE_USERMODE in init/Kconfig.

Thanks,

Mathieu


> 
> Thanks,
> 
> Mathieu
> 
>> 
>> Thanks,
>> 
>> 	tglx
> 
> --
> Mathieu Desnoyers
> EfficiOS Inc.
> http://www.efficios.com

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com