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=-0.6 required=3.0 tests=DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIM_INVALID 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 67971C43334 for ; Thu, 6 Sep 2018 02:56:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EE7EB20652 for ; Thu, 6 Sep 2018 02:56:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="key not found in DNS" (0-bit key) header.d=codeaurora.org header.i=@codeaurora.org header.b="IRSeoFnU"; dkim=fail reason="key not found in DNS" (0-bit key) header.d=codeaurora.org header.i=@codeaurora.org header.b="IRSeoFnU" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EE7EB20652 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727695AbeIFH3f (ORCPT ); Thu, 6 Sep 2018 03:29:35 -0400 Received: from smtp.codeaurora.org ([198.145.29.96]:47412 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726059AbeIFH3f (ORCPT ); Thu, 6 Sep 2018 03:29:35 -0400 Received: by smtp.codeaurora.org (Postfix, from userid 1000) id D925B607B5; Thu, 6 Sep 2018 02:56:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=codeaurora.org; s=default; t=1536202586; bh=6ZXclQG4RV6rQzOwlrK8mLRgw9s+Z9Ya9a+JKHXTv4g=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=IRSeoFnUrxMIDTXekpIxMFCuEnv3W1+9s6/Pb92VRAwhI6gMjCo1zNYvSJi7ymrqk 6dBglyIMzG+3PKKeECw5b/1qdAohM0GU65Q8jXRS7cHO/x029w2Er7qlU6nuv1b+Z+ iWQkNiYpqlko8nPKkE5EF4eEAh2vAWXfhE4xcCIE= Received: from [10.204.78.89] (blr-c-bdr-fw-01_globalnat_allzones-outside.qualcomm.com [103.229.19.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: neeraju@smtp.codeaurora.org) by smtp.codeaurora.org (Postfix) with ESMTPSA id D58706034F; Thu, 6 Sep 2018 02:56:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=codeaurora.org; s=default; t=1536202586; bh=6ZXclQG4RV6rQzOwlrK8mLRgw9s+Z9Ya9a+JKHXTv4g=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=IRSeoFnUrxMIDTXekpIxMFCuEnv3W1+9s6/Pb92VRAwhI6gMjCo1zNYvSJi7ymrqk 6dBglyIMzG+3PKKeECw5b/1qdAohM0GU65Q8jXRS7cHO/x029w2Er7qlU6nuv1b+Z+ iWQkNiYpqlko8nPKkE5EF4eEAh2vAWXfhE4xcCIE= DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org D58706034F Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=none smtp.mailfrom=neeraju@codeaurora.org Subject: Re: [PATCH] cpu/hotplug: Fix rollback during error-out in takedown_cpu() To: Thomas Gleixner Cc: josh@joshtriplett.org, peterz@infradead.org, mingo@kernel.org, jiangshanlai@gmail.com, dzickus@redhat.com, brendan.jackman@arm.com, malat@debian.org, linux-kernel@vger.kernel.org, sramana@codeaurora.org, linux-arm-msm@vger.kernel.org References: <1536042803-6152-1-git-send-email-neeraju@codeaurora.org> <5b0e528f-e597-9598-3ff6-b9e08ddb8165@codeaurora.org> From: Neeraj Upadhyay Message-ID: <9cac90ff-1a43-8663-da2e-7191975b5e93@codeaurora.org> Date: Thu, 6 Sep 2018 08:26:20 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/05/2018 06:47 PM, Thomas Gleixner wrote: > On Wed, 5 Sep 2018, Neeraj Upadhyay wrote: >> On 09/05/2018 05:53 PM, Thomas Gleixner wrote: >>> And looking closer this is a general issue. Just that the TEARDOWN state >>> makes it simple to observe. It's universaly broken, when the first teardown >>> callback fails because, st->state is only decremented _AFTER_ the callback >>> returns success, but undo_cpu_down() increments unconditionally. >>> >> As per my understanding, there are 2 problems here; one is fixed with your >> patch, and other is cpuhp_reset_state() is used during rollback from non-AP to >> AP state, which seem to result in 2 increments of st->state (one increment >> done by cpuhp_reset_state() and another by cpu_thread_fun()) . > And how did your hack fix that up magically? I'll have a look later today. > > Thanks, > > tglx The hack fixes it by not calling cpuhp_reset_state() and doing rollback state reset inline in  _cpu_down(). -- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, hosted by The Linux Foundation