linux-kernel - Re: [RFC PATCH for 4.15 18/24] membarrier: provide SHARED

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Message-ID: <1572576576.15297.1510709771637.JavaMail.zimbra@efficios.com>
Date:   Wed, 15 Nov 2017 01:36:11 +0000 (UTC)
From:   Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Andy Lutomirski <luto@...capital.net>,
        Dave Watson <davejwatson@...com>
Cc:     linux-kernel <linux-kernel@...r.kernel.org>,
        linux-api <linux-api@...r.kernel.org>,
        Paul Turner <pjt@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Russell King <linux@....linux.org.uk>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Andrew Hunter <ahh@...gle.com>,
        Andi Kleen <andi@...stfloor.org>, Chris Lameter <cl@...ux.com>,
        Ben Maurer <bmaurer@...com>, rostedt <rostedt@...dmis.org>,
        Josh Triplett <josh@...htriplett.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Michael Kerrisk <mtk.manpages@...il.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>,
        Andrea Parri <parri.andrea@...il.com>, x86 <x86@...nel.org>
Subject: Re: [RFC PATCH for 4.15 18/24] membarrier: provide SHARED_EXPEDITED
 command

----- On Nov 14, 2017, at 3:04 PM, Mathieu Desnoyers mathieu.desnoyers@...icios.com wrote:
[...]
> +	if (!fallback) {
> +		smp_call_function_many(tmpmask, ipi_mb, NULL, 1);
> +		free_cpumask_var(tmpmask);
> +	}

Testing with preempt debugging options showed that I need to
disable preemption around smp_call_function_many(). The membarrier
private expedited command in 4.14 is also affected. I will add a
fix to the series covering that case separately, and CC stable.

Thanks,

Mathieu

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