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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED 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 7B51DC43381 for ; Thu, 28 Feb 2019 15:42:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 53274218AE for ; Thu, 28 Feb 2019 15:42:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732217AbfB1Pmf convert rfc822-to-8bit (ORCPT ); Thu, 28 Feb 2019 10:42:35 -0500 Received: from bhuna.collabora.co.uk ([46.235.227.227]:53646 "EHLO bhuna.collabora.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727858AbfB1Pme (ORCPT ); Thu, 28 Feb 2019 10:42:34 -0500 Received: from localhost (unknown [IPv6:2a01:e0a:2c:6930:5cf4:84a1:2763:fe0d]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) (Authenticated sender: bbrezillon) by bhuna.collabora.co.uk (Postfix) with ESMTPSA id E1BBA278659; Thu, 28 Feb 2019 15:42:31 +0000 (GMT) Date: Thu, 28 Feb 2019 16:42:28 +0100 From: Boris Brezillon To: "liujian (CE)" Cc: Tokunori Ikegami , "dwmw2@infradead.org" , "computersforpeace@gmail.com" , "bbrezillon@kernel.org" , "marek.vasut@gmail.com" , "richard@nod.at" , "ikegami@allied-telesis.co.jp" , "keescook@chromium.org" , "vigneshr@ti.com" , "linux-mtd@lists.infradead.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH v3] cfi: fix deadloop in cfi_cmdset_0002.c do_write_buffer Message-ID: <20190228164228.734ede80@collabora.com> In-Reply-To: <4F88C5DDA1E80143B232E89585ACE27D0264F137@DGGEMM528-MBX.china.huawei.com> References: <1551189648-58073-1-git-send-email-liujian56@huawei.com> <016001d4cf71$865e7b60$931b7220$@gmail.com> <4F88C5DDA1E80143B232E89585ACE27D0264F137@DGGEMM528-MBX.china.huawei.com> Organization: Collabora X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 28 Feb 2019 15:12:15 +0000 "liujian (CE)" wrote: > > -----Original Message----- > > From: Tokunori Ikegami [mailto:ikegami.t@gmail.com] > > Sent: Thursday, February 28, 2019 10:26 PM > > To: liujian (CE) ; dwmw2@infradead.org; > > computersforpeace@gmail.com; bbrezillon@kernel.org; > > marek.vasut@gmail.com; richard@nod.at; joakim.tjernlund@infinera.com; > > ikegami@allied-telesis.co.jp; keescook@chromium.org; vigneshr@ti.com > > Cc: linux-mtd@lists.infradead.org; linux-kernel@vger.kernel.org > > Subject: RE: [PATCH v3] cfi: fix deadloop in cfi_cmdset_0002.c do_write_buffer > > > > > > > > > -----Original Message----- > > > From: linux-mtd [mailto:linux-mtd-bounces@lists.infradead.org] On > > > Behalf Of Liu Jian > > > Sent: Tuesday, February 26, 2019 11:01 PM > > > To: dwmw2@infradead.org; computersforpeace@gmail.com; > > > bbrezillon@kernel.org; marek.vasut@gmail.com; richard@nod.at; > > > joakim.tjernlund@infinera.com; ikegami@allied-telesis.co.jp; > > > keescook@chromium.org; vigneshr@ti.com > > > Cc: linux-mtd@lists.infradead.org; liujian56@huawei.com; > > > linux-kernel@vger.kernel.org > > > Subject: [PATCH v3] cfi: fix deadloop in cfi_cmdset_0002.c > > > do_write_buffer > > > > > > In function do_write_buffer(), in the for loop, there is a case > > > chip_ready() returns 1 while chip_good() returns 0, so it never break > > > the loop. > > > To fix this, chip_good() is enough and it should timeout if it stay > > > bad for a while. > > > > > > Fixes: dfeae1073583("mtd: cfi_cmdset_0002: Change write buffer to > > > check correct value") > > > Signed-off-by: Yi Huaijie > > > Signed-off-by: Liu Jian > > > Reviewed-by: Tokunori Ikegami > > > --- > > > v2->v3: > > > Follow Vignesh's advice: > > > add one more check for check_good() even when time_after() returns true. > > > > > > drivers/mtd/chips/cfi_cmdset_0002.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/drivers/mtd/chips/cfi_cmdset_0002.c > > > b/drivers/mtd/chips/cfi_cmdset_0002.c > > > index 72428b6..3da2376 100644 > > > --- a/drivers/mtd/chips/cfi_cmdset_0002.c > > > +++ b/drivers/mtd/chips/cfi_cmdset_0002.c > > > @@ -1876,7 +1876,7 @@ static int __xipram do_write_buffer(struct > > > map_info *map, struct flchip *chip, > > > continue; > > > } > > > > > > - if (time_after(jiffies, timeo) && !chip_ready(map, adr)) > > > + if (time_after(jiffies, timeo) && !chip_good(map, adr, > > > datum)) > > > > Just another idea to understand easily. > > > > unsigned long now = jiffies; > > > > if (chip_good(map, adr, datum)) { > > xip_enable(map, chip, adr); > > goto op_done; > > } > > > > if (time_after(now, timeo) { > > break; > > } > > > > Thank you~. It is more easier to understand！ > If there are no other comments, I will send new patch again ): Except this version no longer does what Vignesh suggested. See how you no longer test if chip_good() is true if time_after() returns true. So, imagine the thread entering this function is preempted just after the first chip_good() test, and resumed a few ms later. time_after() will return true, but chip_good() might also return true, and you ignore it.