From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B8A33C43381 for ; Mon, 11 Mar 2019 15:09:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 840552087C for ; Mon, 11 Mar 2019 15:09:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="Bd7ZvUX2" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726826AbfCKPJt (ORCPT ); Mon, 11 Mar 2019 11:09:49 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:45390 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726605AbfCKPJt (ORCPT ); Mon, 11 Mar 2019 11:09:49 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=WBXiJsth6ZRy4NnXvBEm40XbIfkraeDBimeU3qelFzU=; b=Bd7ZvUX2y4PxO1EIn4KySo+3Q eteJtV//cZGYPMH5OL5vGuOHVk9+SgU3zPSwU8836Bm/mfFWELjsiXId8ieTyy8jekyQHhdHCXuWe T1fHnDzr+SPYy6FKgsl6iOHGPcqIzi3M15vR+pXmHKq1wrd5zauFP2NPlDHWh/aHXG76TSECdxVmN 30Z8Q8fRb+EY74Ol1rHXThvErA62J1HtwmWP416mwOl0ChWxJRi6UFB7k6sl2TVqPmijGljMRBhmR xRbcDeOZAXzRWzfGf+RHWt4CeLySYB4CAGMVJQZM21TWtDfg3CwcxtyG08bk7GRlNbY/WwLbwuZ0B BnwtoY5mA==; Received: from willy by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1h3MYl-0004UM-Ib; Mon, 11 Mar 2019 15:09:47 +0000 Date: Mon, 11 Mar 2019 08:09:47 -0700 From: Matthew Wilcox To: Dan Williams Cc: Linux MM , linux-nvdimm , linux-fsdevel , "Barror, Robert" Subject: Re: Hang / zombie process from Xarray page-fault conversion (bisected) Message-ID: <20190311150947.GD19508@bombadil.infradead.org> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.2 (2017-12-15) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Thu, Mar 07, 2019 at 10:16:17PM -0800, Dan Williams wrote: > Hi Willy, > > We're seeing a case where RocksDB hangs and becomes defunct when > trying to kill the process. v4.19 succeeds and v4.20 fails. Robert was > able to bisect this to commit b15cd800682f "dax: Convert page fault > handlers to XArray". > > I see some direct usage of xa_index and wonder if there are some more > pmd fixups to do? > > Other thoughts? I don't see why killing a process would have much to do with PMD misalignment. The symptoms (hanging on a signal) smell much more like leaving a locked entry in the tree. Is this easy to reproduce? Can you get /proc/$pid/stack for a hung task?