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=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, NICE_REPLY_A,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 7F049C43381 for ; Mon, 11 Jan 2021 14:01:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4B47C22472 for ; Mon, 11 Jan 2021 14:01:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387794AbhAKOBU (ORCPT ); Mon, 11 Jan 2021 09:01:20 -0500 Received: from frasgout.his.huawei.com ([185.176.79.56]:2305 "EHLO frasgout.his.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730503AbhAKOBP (ORCPT ); Mon, 11 Jan 2021 09:01:15 -0500 Received: from fraeml736-chm.china.huawei.com (unknown [172.18.147.226]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4DDwFv0qCjz67Zn2; Mon, 11 Jan 2021 21:55:31 +0800 (CST) Received: from lhreml724-chm.china.huawei.com (10.201.108.75) by fraeml736-chm.china.huawei.com (10.206.15.217) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2106.2; Mon, 11 Jan 2021 15:00:33 +0100 Received: from [10.210.171.188] (10.210.171.188) by lhreml724-chm.china.huawei.com (10.201.108.75) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256) id 15.1.2106.2; Mon, 11 Jan 2021 14:00:31 +0000 Subject: Re: [PATCH 00/11] scsi: libsas: Remove in_interrupt() check To: "Ahmed S. Darwish" , Jason Yan CC: Hannes Reinecke , "James E.J. Bottomley" , "Martin K. Petersen" , Daniel Wagner , Artur Paszkiewicz , Jack Wang , , LKML , "Thomas Gleixner" , "Sebastian A. Siewior" References: From: John Garry Message-ID: Date: Mon, 11 Jan 2021 13:59:25 +0000 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.1.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-Originating-IP: [10.210.171.188] X-ClientProxiedBy: lhreml703-chm.china.huawei.com (10.201.108.52) To lhreml724-chm.china.huawei.com (10.201.108.75) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/01/2021 13:43, Ahmed S. Darwish wrote: > Hi John, Jason, > > On Tue, Dec 22, 2020 at 12:54:58PM +0000, John Garry wrote: >> On 22/12/2020 12:30, Jason Yan wrote: >>>>      return event; >>>> >>>> >>>> So default for phy->ha->event_thres is 32, and I can't imagine that >>> The default value is 1024. >> Ah, 32 is the minimum allowed set via sysfs. >> >>>> anyone has ever reconfigured this via sysfs or even required a value >>>> that large. Maybe Jason (cc'ed) knows better. It's an arbitrary >>>> value to say that the PHY is malfunctioning. I do note that there is >>>> the circular path sas_alloc_event() -> sas_notify_phy_event() -> >>>> sas_alloc_event() there also. >>>> >>>> Anyway, if the 32x event memories were per-allocated, maybe there is >>>> a clean method to manage this memory, which even works in atomic >>>> context, so we could avoid this rework (ignoring the context bugs >>>> you reported for a moment). I do also note that the sas_event_cache >>>> size is not huge. >>>> >>> Pre-allocated memory is an option.(Which we have tried at the very >>> beginnig by Wang Yijing.) >> Right, I remember this, but I think the concern was having a proper method >> to manage this pre-allocated memory then. And same problem now. >> >>> Or directly use GFP_ATOMIC is maybe better than passing flags from lldds. >>> >> I think that if we don't really need this, then should not use it. >> > Kind reminder. Do we have any consensus here? > Hi Ahmed, To me, what you're doing seems fine. I was looking for some API to manage small memory pools and which is atomic safe to avoid passing the context flag, but I didn't find such a thing. Just one other thing to mention: I have a patch to remove the indirection in libsas notifiers: https://github.com/hisilicon/kernel-dev/commit/87fcd7e113dc05b7933260e7fa4588dc3730cc2a I was going to send it today. Hopefully, if community has no problem with it, you can make your changes with that in mind. Thanks, John