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=-1.0 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS 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 AF912C43387 for ; Tue, 15 Jan 2019 04:28:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7246420859 for ; Tue, 15 Jan 2019 04:28:38 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=kernel-dk.20150623.gappssmtp.com header.i=@kernel-dk.20150623.gappssmtp.com header.b="1hnhTsOE" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727244AbfAOE2h (ORCPT ); Mon, 14 Jan 2019 23:28:37 -0500 Received: from mail-pl1-f193.google.com ([209.85.214.193]:45921 "EHLO mail-pl1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726976AbfAOE2h (ORCPT ); Mon, 14 Jan 2019 23:28:37 -0500 Received: by mail-pl1-f193.google.com with SMTP id a14so659104plm.12 for ; Mon, 14 Jan 2019 20:28:37 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20150623.gappssmtp.com; s=20150623; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=2tN2sGcytVFY0+Ywgd3h3jYjcEeH9XS+csfG72SxBlE=; b=1hnhTsOEZiVMzvTpyXFrvUON6TXbKq+0+V8oZseLIoe4LOCylFDfiWv/Mzm+XQ75py CqhAKa6tnKZf6prEdBzYkvBuVoaTqtobyrTk+ZwWvBeCrroUJafEmDzG666viGVcH5Tb CPJ7D2OVbXlvk9WsUJQYYIp+NY+C54YGpHey9nzRKJyUOE5NuC/wv1E65Jis2yxtprkn wN3gcxM70/yKt7cUYFFH8UdB+Y0NZW84IQVRPIdkyXa+5mWTlRI5J9mcaZnkCo1ejpYD HfzBHNYJ7B0TlYYJkw1jZdkmXxgtFCUDi/HQZtVA8EivLY35k10fj+kq1zPb0wib1UE1 Zdag== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=2tN2sGcytVFY0+Ywgd3h3jYjcEeH9XS+csfG72SxBlE=; b=TMSCE9VuIAFBqx56m1Ul0Fnr4EWMyI21c7OAqvGQP1adRhvwrcyX9krujRwVg8FfDc Vw5nbejeIXl842vODR0ph+NRCwQw1t+aFiGaFaCWlXFspSydncTIp2qXHkFz39+FeKXO FHYTLFMZULk2qBz6ILBViccWASRTm8Vzou+ZIFtBHgEYPUSXbyM97QQQ7RUAGG95OQP4 BV+kHVgEbVfvkAPMYOYk4tlb2FgAua3ExLpiaKHLCci72oySvbCgHLuD28DIZiFuI1GF ddylTGMzEhdGulcOvbeL5gHxsPdKlmlZyXsYuABAd5wYLcCfaquCGZGchF5vqUS7oI1m YFuw== X-Gm-Message-State: AJcUukd85yvI34K+c08pbCCI/4O2briu4XwbzMB8LQtKy0iYSQmDEB5S P8DsTuieT6395jq3iEBPMaRVN70/Cyvb+g== X-Google-Smtp-Source: ALg8bN66ctkOZ42Zqnq/Yrz89S+7Yao8f05uQZpY9H8hx5gZlFWOgDVZHZtLiCFYknv45shbKiA3fg== X-Received: by 2002:a17:902:8d95:: with SMTP id v21mr2124047plo.162.1547526517063; Mon, 14 Jan 2019 20:28:37 -0800 (PST) Received: from [192.168.1.121] (66.29.188.166.static.utbb.net. [66.29.188.166]) by smtp.gmail.com with ESMTPSA id v184sm2256197pfb.182.2019.01.14.20.28.34 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 14 Jan 2019 20:28:35 -0800 (PST) Subject: Re: [PATCH] sbitmap: Protect swap_lock from hardirq To: Ming Lei Cc: linux-block@vger.kernel.org, Clark Williams , Guenter Roeck , Steven Rostedt , Linus Torvalds , linux-kernel@vger.kernel.org References: <20190115035952.13325-1-ming.lei@redhat.com> From: Jens Axboe Message-ID: Date: Mon, 14 Jan 2019 21:28:33 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: <20190115035952.13325-1-ming.lei@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 1/14/19 8:59 PM, Ming Lei wrote: > The original report is actually one real deadlock: > > [ 106.132865] Possible interrupt unsafe locking scenario: > [ 106.132865] > [ 106.133659] CPU0 CPU1 > [ 106.134194] ---- ---- > [ 106.134733] lock(&(&sb->map[i].swap_lock)->rlock); > [ 106.135318] local_irq_disable(); > [ 106.136014] lock(&sbq->ws[i].wait); > [ 106.136747] lock(&(&hctx->dispatch_wait_lock)->rlock); > [ 106.137742] > [ 106.138110] lock(&sbq->ws[i].wait); > > Because we may call blk_mq_get_driver_tag() directly from > blk_mq_dispatch_rq_list() without holding any lock, then HARDIRQ may come > and the above DEADLOCK is triggered. > > ab53dcfb3e7b ("sbitmap: Protect swap_lock from hardirq") tries to fix > this issue by using 'spin_lock_bh', which isn't enough because we complete > request from hardirq context direclty in case of multiqueue. Thanks Ming, I'll queue this up for shipping this week. -- Jens Axboe