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=-8.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_PASS,USER_AGENT_NEOMUTT autolearn=unavailable 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 E71A5C282DA for ; Mon, 15 Apr 2019 15:20:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B66D4217D6 for ; Mon, 15 Apr 2019 15:20:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727667AbfDOPUb (ORCPT ); Mon, 15 Apr 2019 11:20:31 -0400 Received: from Galois.linutronix.de ([146.0.238.70]:46192 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727252AbfDOPUb (ORCPT ); Mon, 15 Apr 2019 11:20:31 -0400 Received: from bigeasy by Galois.linutronix.de with local (Exim 4.80) (envelope-from ) id 1hG3PC-0003Uz-Bo; Mon, 15 Apr 2019 17:20:22 +0200 Date: Mon, 15 Apr 2019 17:20:22 +0200 From: Sebastian Andrzej Siewior To: Kirill Smelkov Cc: Julia Lawall , kbuild-all@01.org, Kurt Schwemmer , Logan Gunthorpe , Bjorn Helgaas , linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] pci/switchtec: fix stream_open.cocci warnings (fwd) Message-ID: <20190415152021.3j3riefeoz7rf2pa@linutronix.de> References: <20190413170056.GA11293@deco.navytux.spb.ru> <20190415143857.kg2dbg3zxsxdktsi@linutronix.de> <20190415145456.GA15280@deco.navytux.spb.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190415145456.GA15280@deco.navytux.spb.ru> User-Agent: NeoMutt/20180716 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2019-04-15 14:55:02 [+0000], Kirill Smelkov wrote: > Hi Sebastian, Hi Kirill, > On Mon, Apr 15, 2019 at 04:38:57PM +0200, Sebastian Andrzej Siewior wrote: > > On 2019-04-13 17:00:59 [+0000], Kirill Smelkov wrote: > > > stream_open.cocci was issuing only warning for pci/switchtec, but after > > > 8a29a3bae2a2 ("pci/switchtec: Don't use completion's wait queue") they > > > started to use wait_even_* inside read method and, since > > > stream_open.cocci considers wait_event_* as blocking the warning became > > > error. Previously it was completions there, but I added support for wait > > > events only for simplicity. > > > > why is wait_event_interruptible() treated differently compared to > > wait_for_completion_interruptible()? > > No particular reason. I just taught stream_open.cocci to consider > only "wait_event_*" as blocking: > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/scripts/coccinelle/api/stream_open.cocci?h=v5.1-rc5#n35 > > based on original /proc/xen/xenbus deadlock: > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/xen/xenbus/xenbus_dev_frontend.c?h=v5.1-rc5#n135 > https://git.kernel.org/linus/581d21a2d02a > > We can extend "a function that blocks" rule to cover other kernel > primitives. > > For the reference: the deadlock scenario is described in > > https://git.kernel.org/linus/10dce8af3422 As far I understand the problem is when the ->read() callback waits for the ->write() callback. The locking isn't changed by patch you mentioned. So extended might make sense. But then wait_event_* by itself in ->read() isn't a problem as long as its counter part isn't in ->write(). But yes, nice finding. > Kirill Sebastian