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=-8.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_HELO_NONE,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 434A2C433DB for ; Tue, 9 Feb 2021 05:34:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E8E6364EB1 for ; Tue, 9 Feb 2021 05:34:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229753AbhBIFek convert rfc822-to-8bit (ORCPT ); Tue, 9 Feb 2021 00:34:40 -0500 Received: from szxga01-in.huawei.com ([45.249.212.187]:2581 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229517AbhBIFej (ORCPT ); Tue, 9 Feb 2021 00:34:39 -0500 Received: from DGGEMM405-HUB.china.huawei.com (unknown [172.30.72.53]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4DZWj933nkzW18j; Tue, 9 Feb 2021 13:31:41 +0800 (CST) Received: from dggemi709-chm.china.huawei.com (10.3.20.108) by DGGEMM405-HUB.china.huawei.com (10.3.20.213) with Microsoft SMTP Server (TLS) id 14.3.498.0; Tue, 9 Feb 2021 13:33:56 +0800 Received: from dggemi761-chm.china.huawei.com (10.1.198.147) by dggemi709-chm.china.huawei.com (10.3.20.108) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2106.2; Tue, 9 Feb 2021 13:33:55 +0800 Received: from dggemi761-chm.china.huawei.com ([10.9.49.202]) by dggemi761-chm.china.huawei.com ([10.9.49.202]) with mapi id 15.01.2106.006; Tue, 9 Feb 2021 13:33:55 +0800 From: "Song Bao Hua (Barry Song)" To: Finn Thain CC: tanxiaofei , "jejb@linux.ibm.com" , "martin.petersen@oracle.com" , "linux-scsi@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linuxarm@openeuler.org" , "linux-m68k@vger.kernel.org" Subject: RE: [Linuxarm] Re: [PATCH for-next 00/32] spin lock usage optimization for SCSI drivers Thread-Topic: [Linuxarm] Re: [PATCH for-next 00/32] spin lock usage optimization for SCSI drivers Thread-Index: AQHW/fAMrBMz1ua2YUiLJwcWnjqnW6pPDROA//+zewCAAIlDYA== Date: Tue, 9 Feb 2021 05:33:55 +0000 Message-ID: <6712a7f16b99489db2828098dc3e03b2@hisilicon.com> References: <1612697823-8073-1-git-send-email-tanxiaofei@huawei.com> <31cd807d-3d0-ed64-60d-fde32cb3833c@telegraphics.com.au> In-Reply-To: Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.126.200.92] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-m68k@vger.kernel.org > -----Original Message----- > From: Finn Thain [mailto:fthain@telegraphics.com.au] > Sent: Tuesday, February 9, 2021 6:06 PM > To: Song Bao Hua (Barry Song) > Cc: tanxiaofei ; jejb@linux.ibm.com; > martin.petersen@oracle.com; linux-scsi@vger.kernel.org; > linux-kernel@vger.kernel.org; linuxarm@openeuler.org; > linux-m68k@vger.kernel.org > Subject: RE: [Linuxarm] Re: [PATCH for-next 00/32] spin lock usage optimization > for SCSI drivers > > On Tue, 9 Feb 2021, Song Bao Hua (Barry Song) wrote: > > > > -----Original Message----- > > > From: Finn Thain [mailto:fthain@telegraphics.com.au] > > > Sent: Monday, February 8, 2021 8:57 PM > > > To: tanxiaofei > > > Cc: jejb@linux.ibm.com; martin.petersen@oracle.com; > > > linux-scsi@vger.kernel.org; linux-kernel@vger.kernel.org; > > > linuxarm@openeuler.org > > > Subject: [Linuxarm] Re: [PATCH for-next 00/32] spin lock usage optimization > > > for SCSI drivers > > > > > > On Sun, 7 Feb 2021, Xiaofei Tan wrote: > > > > > > > Replace spin_lock_irqsave with spin_lock in hard IRQ of SCSI drivers. > > > > There are no function changes, but may speed up if interrupt happen too > > > > often. > > > > > > This change doesn't necessarily work on platforms that support nested > > > interrupts. > > > > > > Were you able to measure any benefit from this change on some other > > > platform? > > > > I think the code disabling irq in hardIRQ is simply wrong. > > Since this commit > > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/ > ?id=e58aa3d2d0cc > > genirq: Run irq handlers with interrupts disabled > > > > interrupt handlers are definitely running in a irq-disabled context > > unless irq handlers enable them explicitly in the handler to permit > > other interrupts. > > > > Repeating the same claim does not somehow make it true. If you put your Sorry for I didn't realize xiaofei had replied. > claim to the test, you'll see that that interrupts are not disabled on > m68k when interrupt handlers execute. Sounds like an implementation issue of m68k since IRQF_DISABLED has been totally removed. > > The Interrupt Priority Level (IPL) can prevent any given irq handler from > being re-entered, but an irq with a higher priority level may be handled > during execution of a lower priority irq handler. > We used to have IRQF_DISABLED to support so-called "fast interrupt" to avoid this. But the concept has been totally removed. That is interesting if m68k still has this issue. > sonic_interrupt() uses an irq lock within an interrupt handler to avoid > issues relating to this. This kind of locking may be needed in the drivers > you are trying to patch. Or it might not. Apparently, no-one has looked. Thanks Barry