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Thu, 22 Aug 2019 22:13:18 +0000 Received: from pps.filterd (userp3030.oracle.com [127.0.0.1]) by userp3030.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x7MM41UL194552; Thu, 22 Aug 2019 22:13:18 GMT Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by userp3030.oracle.com with ESMTP id 2uh2q6hut4-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 22 Aug 2019 22:13:17 +0000 Received: from abhmp0012.oracle.com (abhmp0012.oracle.com [141.146.116.18]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id x7MMDGP6005900; Thu, 22 Aug 2019 22:13:16 GMT Received: from [192.168.1.219] (/98.229.125.203) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Thu, 22 Aug 2019 15:13:16 -0700 Subject: Re: [PATCH 8/9] padata: unbind parallel jobs from specific CPUs To: Herbert Xu Cc: Steffen Klassert , Lai Jiangshan , Peter Zijlstra , Tejun Heo , linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org References: <20190813005224.30779-1-daniel.m.jordan@oracle.com> <20190813005224.30779-9-daniel.m.jordan@oracle.com> <20190822041340.GA590@gondor.apana.org.au> From: Daniel Jordan Message-ID: Date: Thu, 22 Aug 2019 18:13:15 -0400 MIME-Version: 1.0 In-Reply-To: <20190822041340.GA590@gondor.apana.org.au> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9357 signatures=668684 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=2 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1906280000 definitions=main-1908220194 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9357 signatures=668684 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=2 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1906280000 definitions=main-1908220194 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/22/19 12:13 AM, Herbert Xu wrote: > 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. So we can, thanks for catching that.