Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S965161AbeALSTH (ORCPT <rfc822;ralf@linux-mips.org> + 1 other);
        Fri, 12 Jan 2018 13:19:07 -0500
Received: from bombadil.infradead.org ([65.50.211.133]:39406 "EHLO
        bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S964867AbeALSTG (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Fri, 12 Jan 2018 13:19:06 -0500
Date: Fri, 12 Jan 2018 10:18:40 -0800
From: Matthew Wilcox <willy@infradead.org>
To: Laurent Dufour <ldufour@linux.vnet.ibm.com>
Cc: paulmck@linux.vnet.ibm.com, peterz@infradead.org,
        akpm@linux-foundation.org, kirill@shutemov.name,
        ak@linux.intel.com, mhocko@kernel.org, dave@stgolabs.net,
        jack@suse.cz, benh@kernel.crashing.org, mpe@ellerman.id.au,
        paulus@samba.org, Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, hpa@zytor.com,
        Will Deacon <will.deacon@arm.com>,
        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Alexei Starovoitov <alexei.starovoitov@gmail.com>,
        kemi.wang@intel.com, sergey.senozhatsky.work@gmail.com,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        haren@linux.vnet.ibm.com, khandual@linux.vnet.ibm.com,
        npiggin@gmail.com, bsingharora@gmail.com,
        Tim Chen <tim.c.chen@linux.intel.com>,
        linuxppc-dev@lists.ozlabs.org, x86@kernel.org
Subject: Re: [PATCH v6 18/24] mm: Try spin lock in speculative path
Message-ID: <20180112181840.GA7590@bombadil.infradead.org>
References: <1515777968-867-1-git-send-email-ldufour@linux.vnet.ibm.com>
 <1515777968-867-19-git-send-email-ldufour@linux.vnet.ibm.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <1515777968-867-19-git-send-email-ldufour@linux.vnet.ibm.com>
User-Agent: Mutt/1.9.1 (2017-09-22)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Return-Path: <linux-kernel-owner@vger.kernel.org>

On Fri, Jan 12, 2018 at 06:26:02PM +0100, Laurent Dufour wrote:
> There is a deadlock when a CPU is doing a speculative page fault and
> another one is calling do_unmap().
> 
> The deadlock occurred because the speculative path try to spinlock the
> pte while the interrupt are disabled. When the other CPU in the
> unmap's path has locked the pte then is waiting for all the CPU to
> invalidate the TLB. As the CPU doing the speculative fault have the
> interrupt disable it can't invalidate the TLB, and can't get the lock.
> 
> Since we are in a speculative path, we can race with other mm action.
> So let assume that the lock may not get acquired and fail the
> speculative page fault.

It seems like you introduced this bug in the previous patch, and now
you're fixing it in this patch?  Why not merge the two?