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=-2.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 35D1BC2D0EF for ; Sat, 18 Apr 2020 11:25:53 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id F206F21D79 for ; Sat, 18 Apr 2020 11:25:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="Q2PsPEwb" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F206F21D79 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date: Message-ID:From:References:To:Subject:Reply-To:Content-ID:Content-Description :Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=psJJtiu/k5fhVTmjhwzswITnXWOOBoC8RkIz+9vbeMI=; b=Q2PsPEwbbBAESW c+8W9NTlzbLgTGgL1OFAigZDveLUm2n737piNAe0+e5pF8Z9mOvAM8qDe+3WzVs/DsfHE8h35B3il Zul2PlY8vlIFNPdZjVBV50XOtSfL3SRrxuClu0d3jtl5I9hmGHHuLQYENK0mNfg2eQjEKcqSPk0+a ApnvCA3kOCqSSu9j96s2X/PU3fp1okYSC5NgiQKXvY3kiQqMZvlqEhrmilfHLMsB95WluzE0UpqZi VN1Mp2UTvigNXEuG32+BRn0XCnfLCBdQ2taJ5VFCOuDlyV34ht/U/+dBOljBVCubz7dGbYjvSwBo7 OrLtPltyEDP4/0grek8A==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jPlbb-0000vs-UH; Sat, 18 Apr 2020 11:25:51 +0000 Received: from szxga06-in.huawei.com ([45.249.212.32] helo=huawei.com) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jPlbY-0000ug-HJ for linux-arm-kernel@lists.infradead.org; Sat, 18 Apr 2020 11:25:50 +0000 Received: from DGGEMS404-HUB.china.huawei.com (unknown [172.30.72.59]) by Forcepoint Email with ESMTP id 9934FD8AB4B7ECB6709C; Sat, 18 Apr 2020 19:25:35 +0800 (CST) Received: from [127.0.0.1] (10.74.184.86) by DGGEMS404-HUB.china.huawei.com (10.3.19.204) with Microsoft SMTP Server id 14.3.487.0; Sat, 18 Apr 2020 19:25:29 +0800 Subject: Re: Question about SEA handling process happened in user space To: James Morse References: <5E81EFCD.6020605@huawei.com> <2b0e5507-ad75-9af1-6afe-aa87d8cf597f@arm.com> <5E8587A3.6030101@huawei.com> <558ffd42-74d7-e364-2b79-93ab0998ab6e@arm.com> <5E8EE845.8090406@huawei.com> <66db5a6a-e68b-00b7-6a78-2c8cd9e63aab@arm.com> <5E903FDD.4080106@huawei.com> From: Xiaofei Tan Message-ID: <5E9AE3A9.5020904@huawei.com> Date: Sat, 18 Apr 2020 19:25:29 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.5.1 MIME-Version: 1.0 In-Reply-To: X-Originating-IP: [10.74.184.86] X-CFilter-Loop: Reflected X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200418_042549_143300_ECC79C22 X-CRM114-Status: UNSURE ( 9.26 ) X-CRM114-Notice: Please train this message. X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Catalin Marinas , Linuxarm , Will Deacon , Dave Martin , linux-arm-kernel@lists.infradead.org, Shiju Jose Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi James On 2020/4/16 21:50, James Morse wrote: > On 10/04/2020 10:43, Xiaofei Tan wrote: >> On 2020/4/9 22:28, James Morse wrote: >>> On 09/04/2020 10:17, Xiaofei Tan wrote: >>>> On 2020/4/8 0:37, James Morse wrote: >>>>> With that series, it runs in process-context as task-work. memory_failure() needs to >>>>> sleep, so it has to run in process-context. > >>>>> Doing it as task-work means it runs before the thread returns to user-space. >>>> >>>> Sorry, i don't understand this. i thought the task-work need to reschedule, and current thread should >>>> have returned to user-space before it. >>> >>> ret_to_user has a loop around do_notify_resume(), if the _TIF_NOTIFY_RESUME flag is set >>> and we call tracehook_notify_resume() which ends up in task_work_run()... >>> >>> That TIF flag effectively prevents this thread returning to user-space until that task >>> work has run. > >> Got it. This function is great. > > I think PeterZ pointed me at it, > Great. > >> BTW, i have not found the place of setting the flag _TIF_NOTIFY_RESUME. Is it set by default for each thread? > > With that series, APEI calls task_work_add(), which calls set_notify_resume() from > include/linux/tracehook.h > | if (!test_and_set_tsk_thread_flag(task, TIF_NOTIFY_RESUME)) > Got it. thanks. > > Thanks, > > James > > . > -- thanks tanxiaofei _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel