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[156.34.55.100]) by smtp.gmail.com with ESMTPSA id n18sm29218512qtr.28.2019.07.31.16.00.57 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 31 Jul 2019 16:00:58 -0700 (PDT) Received: from jgg by mlx.ziepe.ca with local (Exim 4.90_1) (envelope-from ) id 1hsxab-00009Y-B9; Wed, 31 Jul 2019 20:00:57 -0300 Date: Wed, 31 Jul 2019 20:00:57 -0300 From: Jason Gunthorpe To: Jason Wang Cc: "Michael S. Tsirkin" , syzbot , aarcange@redhat.com, akpm@linux-foundation.org, christian@brauner.io, davem@davemloft.net, ebiederm@xmission.com, elena.reshetova@intel.com, guro@fb.com, hch@infradead.org, james.bottomley@hansenpartnership.com, jglisse@redhat.com, keescook@chromium.org, ldv@altlinux.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-parisc@vger.kernel.org, luto@amacapital.net, mhocko@suse.com, mingo@kernel.org, namit@vmware.com, peterz@infradead.org, syzkaller-bugs@googlegroups.com, viro@zeniv.linux.org.uk, wad@chromium.org Subject: Re: WARNING in __mmdrop Message-ID: <20190731230057.GA32346@ziepe.ca> References: <20190726094756-mutt-send-email-mst@kernel.org> <0792ee09-b4b7-673c-2251-e5e0ce0fbe32@redhat.com> <20190729045127-mutt-send-email-mst@kernel.org> <4d43c094-44ed-dbac-b863-48fc3d754378@redhat.com> <20190729104028-mutt-send-email-mst@kernel.org> <96b1d67c-3a8d-1224-e9f0-5f7725a3dc10@redhat.com> <20190730110633-mutt-send-email-mst@kernel.org> <421a1af6-df06-e4a6-b34f-526ac123bc4a@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <421a1af6-df06-e4a6-b34f-526ac123bc4a@redhat.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 31, 2019 at 04:49:32PM +0800, Jason Wang wrote: > Yes, looking at the synchronization implemented by other MMU notifiers. > Vhost is even the simplest. I think that is only because it calls gup under a spinlock, which is, IMHO, not great. Jason