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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 12AD7C41514 for ; Thu, 22 Aug 2019 04:14:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DBE8622CE3 for ; Thu, 22 Aug 2019 04:13:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730890AbfHVEN6 (ORCPT ); Thu, 22 Aug 2019 00:13:58 -0400 Received: from helcar.hmeau.com ([216.24.177.18]:58330 "EHLO fornost.hmeau.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725294AbfHVEN6 (ORCPT ); Thu, 22 Aug 2019 00:13:58 -0400 Received: from gondolin.me.apana.org.au ([192.168.0.6] helo=gondolin.hengli.com.au) by fornost.hmeau.com with esmtps (Exim 4.89 #2 (Debian)) id 1i0eTq-0001w2-S9; Thu, 22 Aug 2019 14:13:46 +1000 Received: from herbert by gondolin.hengli.com.au with local (Exim 4.80) (envelope-from ) id 1i0eTk-00009t-MR; Thu, 22 Aug 2019 14:13:40 +1000 Date: Thu, 22 Aug 2019 14:13:40 +1000 From: Herbert Xu To: Daniel Jordan Cc: Steffen Klassert , Lai Jiangshan , Peter Zijlstra , Tejun Heo , linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 8/9] padata: unbind parallel jobs from specific CPUs Message-ID: <20190822041340.GA590@gondor.apana.org.au> References: <20190813005224.30779-1-daniel.m.jordan@oracle.com> <20190813005224.30779-9-daniel.m.jordan@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190813005224.30779-9-daniel.m.jordan@oracle.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 12, 2019 at 08:52:23PM -0400, Daniel Jordan wrote: > > @@ -191,22 +184,25 @@ static struct padata_priv *padata_get_next(struct parallel_data *pd) > padata = list_entry(reorder->list.next, > struct padata_priv, list); > > - list_del_init(&padata->list); > - atomic_dec(&pd->reorder_objects); > + /* > + * The check fails in the unlikely event that two or more > + * parallel jobs have hashed to the same CPU and one of the > + * later ones finishes first. > + */ > + if (padata->seq_nr == pd->processed) { > + list_del_init(&padata->list); > + atomic_dec(&pd->reorder_objects); Now that you've changed the test for whether there is work to be done you also need to update the code at the end of padata_reorder that checks whether there is work to do. Otherwise we can end up in a busy loop that just wastes CPU cycles. Cheers, -- Email: Herbert Xu Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt