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=-8.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 157C6C76188 for ; Tue, 16 Jul 2019 13:15:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DC9E82173C for ; Tue, 16 Jul 2019 13:15:39 +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="KDexd3gO" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728470AbfGPNPj (ORCPT ); Tue, 16 Jul 2019 09:15:39 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:60208 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728387AbfGPNPi (ORCPT ); Tue, 16 Jul 2019 09:15:38 -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=7ES3PIEwIKlpc8yeZqCcy+3GMlubNnq9R+cjjP/ZkFA=; b=KDexd3gOaL6nWm+EGPUyUsNB7 SSEWeRGUFI/5JEm/W2MdiDIP9MCZadRbIj+cIsd63qeOzHJRLPPxbGkEf3Wxq8+pwpk3YpqYx5nQZ qLQDrItjT0rZ8vCOC+zCKizhOqkoJG2vetAVwwWriTWA0HuzeR9zGfoWLaEGoOq/0p+H6vmv1pwns 85v4LcdS1sveFj4jHUSHu0YsJQDmHtcVvsLisi5/RL4Rvd9aXIOp0QlIuNvotEHM1NR+oyoG5hHiP IUMkyjLTGPHF1pzQ02WXLQBG1xan4S4ymQwSxFPA2zh/XKZoqD+uinl9/JI2lLobwehpUOPZo0bam v+BQdeViw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92 #3 (Red Hat Linux)) id 1hnNIg-0003H0-6F; Tue, 16 Jul 2019 13:15:22 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 9E93620B172D1; Tue, 16 Jul 2019 15:15:20 +0200 (CEST) Date: Tue, 16 Jul 2019 15:15:20 +0200 From: Peter Zijlstra To: Herbert Xu Cc: Steffen Klassert , Daniel Jordan , andrea.parri@amarulasolutions.com, boqun.feng@gmail.com, paulmck@linux.ibm.com, linux-arch@vger.kernel.org, linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] padata: Use RCU when fetching pd from do_serial Message-ID: <20190716131520.GB3402@hirez.programming.kicks-ass.net> References: <20190711221205.29889-1-daniel.m.jordan@oracle.com> <20190712100636.mqdr567p7ozanlyl@gondor.apana.org.au> <20190712101012.GW14601@gauss3.secunet.de> <20190712160737.iniaaxlsnhs6azg5@ca-dmjordan1.us.oracle.com> <20190713050321.c5wq7a7jrb6q2pxn@gondor.apana.org.au> <20190715161045.zqwgsp62uqjnvx3l@ca-dmjordan1.us.oracle.com> <20190716100447.pdongriwwfxsuajf@gondor.apana.org.au> <20190716111410.GN17989@gauss3.secunet.de> <20190716125704.l2jolyyd3bue6hhn@gondor.apana.org.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190716125704.l2jolyyd3bue6hhn@gondor.apana.org.au> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-crypto-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org On Tue, Jul 16, 2019 at 08:57:04PM +0800, Herbert Xu wrote: > On Tue, Jul 16, 2019 at 01:14:10PM +0200, Steffen Klassert wrote: > > > > Maybe we can fix it if we call padata_free_pd() from > > padata_serial_worker() when it sent out the last object. > > How about using RCU? > > We still need to fix up the refcnt if it's supposed to limit the > overall number of outstanding requests. > > ---8<--- > The function padata_do_serial uses parallel_data without obeying > the RCU rules around its life-cycle. This means that a concurrent > padata_replace call can result in a crash. > > This patch fixes it by using RCU just as we do in padata_do_parallel. > > Fixes: 16295bec6398 ("padata: Generic parallelization/...") > Signed-off-by: Herbert Xu > diff --git a/kernel/padata.c b/kernel/padata.c > index 2d2fddbb7a4c..fb5dd1210d2b 100644 > --- a/kernel/padata.c > +++ b/kernel/padata.c > @@ -128,7 +128,7 @@ int padata_do_parallel(struct padata_instance *pinst, > > err = 0; > atomic_inc(&pd->refcnt); > - padata->pd = pd; > + padata->inst = pinst; > padata->cb_cpu = cb_cpu; > > target_cpu = padata_cpu_hash(pd); > @@ -367,7 +368,7 @@ void padata_do_serial(struct padata_priv *padata) > struct parallel_data *pd; > int reorder_via_wq = 0; > > - pd = padata->pd; > + pd = rcu_dereference_bh(padata->inst->pd); > > cpu = get_cpu(); > That's weird for not having a matching assign and lacking comments to explain that.