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 3A36BC2BB85 for ; Thu, 16 Apr 2020 13:50:27 +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 0885C21734 for ; Thu, 16 Apr 2020 13:50:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="JME1efux" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0885C21734 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.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=xZ5dUMh9PaXyTATRhnnkXMKlXxMAQ1eLmYDaMhJM/S4=; b=JME1efuxgFybD9 VGCCyZUJBuRKhVCgyb0cfbqfDkZzJN/HaRJ4IwK5Y32+9Y1x9fa1lDiXDltHD9bpFiFDRvnMonB2Z qJKqplBsS1nHF0w+vhLDzcGQ79BGCrZj4JmEPdTf7U8FNVUFAhsIP4Azxpwu6OWzrwYb4HCm8YLA3 blzEJDtkaJy/TBzS1SbLEg5VkltrXEtwB84jZiZnE7B/Y4WB9nvdnlwseMW4HezkRhaxKybdtW3Dw 7vB4PNhLnZv4dWgegMDIUdvTBLbEBbOYqhiExV4b8CsZSg5b/ZDBlBui1phHUhVGW8/3NfnkTBgt9 QcvX2dcNblAclvstGgWQ==; 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 1jP4uN-00009S-IE; Thu, 16 Apr 2020 13:50:23 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jP4uK-00008r-0o for linux-arm-kernel@lists.infradead.org; Thu, 16 Apr 2020 13:50:21 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 1A6471FB; Thu, 16 Apr 2020 06:50:19 -0700 (PDT) Received: from [192.168.0.14] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 21E553F237; Thu, 16 Apr 2020 06:50:18 -0700 (PDT) Subject: Re: Question about SEA handling process happened in user space To: Xiaofei Tan 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: James Morse Message-ID: Date: Thu, 16 Apr 2020 14:50:16 +0100 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <5E903FDD.4080106@huawei.com> Content-Language: en-GB X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200416_065020_104890_25BADE2D X-CRM114-Status: GOOD ( 10.53 ) 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 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, > 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)) Thanks, James _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel