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=-12.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,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 B2A5AC433DB for ; Thu, 11 Feb 2021 08:26:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6C4C564DDF for ; Thu, 11 Feb 2021 08:26:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229636AbhBKI02 (ORCPT ); Thu, 11 Feb 2021 03:26:28 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46986 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229533AbhBKI0M (ORCPT ); Thu, 11 Feb 2021 03:26:12 -0500 Received: from mail-oi1-x22f.google.com (mail-oi1-x22f.google.com [IPv6:2607:f8b0:4864:20::22f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D2E4CC061574 for ; Thu, 11 Feb 2021 00:25:31 -0800 (PST) Received: by mail-oi1-x22f.google.com with SMTP id l19so5210062oih.6 for ; Thu, 11 Feb 2021 00:25:31 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=Ym0jR5L0N+bS9wIXXqHqiV2OVAU2wxDNbKISqR4qPM0=; b=jifqTGabTgKIOgqD96/VwvtjeWDivkIJo68qMVwLTjlHS5+FOWtcYhWk+LVX25vxv2 vPMCE4UaTRWzSaN+V1RTxJbgc3wMG4m+sOZcQzjmJPl8RiybXiloPuDnzhQIw6NryoEo z01OOTiWxcqtn4+m3NEowFBhPg+dAeUAMGsGc0fKhrFk0qM+j0nG3p0bzr40VWfILW0Q zB4isAj20azh+qea7AZoGJ+ToAX2DJROOmhKQBNBGR4+6w+ENlHT5ZGwOoF46CrFlwP8 h4U/9C/c4QHUxxNvGdAJcPjyrTFaFNkbfgajM+zN+L47VyAP+5uolhWTChKlc7pgThll R4Ww== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=Ym0jR5L0N+bS9wIXXqHqiV2OVAU2wxDNbKISqR4qPM0=; b=Jeg8sFjmm4qvx8S9eKH/m1rn6Ntukb2VALnsY+8a6y4Uh+ltIQtG2h2eixq0gpU+Ft 5UDuuYus33mRsHChQ5aRDSAA6RugCZqaQyeC9Gjn2JCQZxM36S1VUFZchVilbW02Vg6Q S3nXktg3NWj/sYg137Vvqm2NWtE2LLk8yiDh8RIUS6FPUVLdd9+tsQP4oFcr42ayjl3r OVTCpoZKbuhv4OWgU7pvhrPRjHir4mG8MHwN3PhQgRHAsK0SSIS7nmuvK1mBfIqupLP9 4Rwemoj2rORt0bJc93fofJ/XsNJ5d2DIBVWORlj35M4uaICJCuWkGn/hr8OO4/dASUOy 9i5g== X-Gm-Message-State: AOAM5308Q/oAbLZ3DOZBh0aFzymL2BBoXxrjIxPPfs4kuqZZS8ZGeBE6 lomghFa4NyMyTmg4K6U0OL8cEGb5h/tH8BTJVHl6aN/0Hm4= X-Google-Smtp-Source: ABdhPJzWotoUOULksEQYw9+7R2LD9Xy+n0hT1syk+opwYHie9Z28QMncK+SW9PlIjrBlWlqJPDCik2kNXDxmKjKamn4= X-Received: by 2002:aca:b655:: with SMTP id g82mr1982089oif.91.1613031931177; Thu, 11 Feb 2021 00:25:31 -0800 (PST) MIME-Version: 1.0 References: <1612923676-18294-1-git-send-email-guoqing.jiang@cloud.ionos.com> In-Reply-To: From: Jack Wang Date: Thu, 11 Feb 2021 09:25:20 +0100 Message-ID: Subject: Re: [PATCH] md: don't unregister sync_thread with reconfig_mutex held To: Song Liu Cc: Guoqing Jiang , linux-raid Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-raid@vger.kernel.org Song Liu =E4=BA=8E2021=E5=B9=B42=E6=9C=8811=E6=97=A5=E5= =91=A8=E5=9B=9B =E4=B8=8A=E5=8D=888:31=E5=86=99=E9=81=93=EF=BC=9A > > On Tue, Feb 9, 2021 at 6:22 PM Guoqing Jiang > wrote: > > > > Unregister sync_thread doesn't need to hold reconfig_mutex since it > > doesn't reconfigure array. > > > > And it could cause deadlock problem for raid5 as follows: > > > > 1. process A tried to reap sync thread with reconfig_mutex held after e= cho > > idle to sync_action. > > 2. raid5 sync thread was blocked if there were too many active stripes. > > 3. SB_CHANGE_PENDING was set (because of write IO comes from upper laye= r) > > which causes the number of active stripes can't be decreased. > > 4. SB_CHANGE_PENDING can't be cleared since md_check_recovery was not a= ble > > to hold reconfig_mutex. > > > > More details in the link: > > issu://lore.kernel.org/linux-raid/5ed54ffc-ce82-bf66-4eff-390cb23bc1ac@= molgen.mpg.de/T/#t > > > > Reported-and-tested-by: Donald Buczek > > Signed-off-by: Guoqing Jiang > > Thanks for debugging the issue. However, I am not sure whether this is > the proper > fix. For example, would this break dm-raid.c:raid_message()? IIUC, > raid_message() > calls md_reap_sync_thread() without holding reconfigure_mutex, no? > > Thanks, > Song. right. A simple solution would be add a parameter to md_reap_sync_thread to indicate if a reconfigure_mutex lock is held. Regards! Jack > > > --- > > drivers/md/md.c | 5 +++++ > > 1 file changed, 5 insertions(+) > > > > diff --git a/drivers/md/md.c b/drivers/md/md.c > > index ca40942..eec8c27 100644 > > --- a/drivers/md/md.c > > +++ b/drivers/md/md.c > > @@ -9365,13 +9365,18 @@ void md_check_recovery(struct mddev *mddev) > > EXPORT_SYMBOL(md_check_recovery); > > > > void md_reap_sync_thread(struct mddev *mddev) > > + __releases(&mddev->reconfig_mutex) > > + __acquires(&mddev->reconfig_mutex) > > + > > { > > struct md_rdev *rdev; > > sector_t old_dev_sectors =3D mddev->dev_sectors; > > bool is_reshaped =3D false; > > > > /* resync has finished, collect result */ > > + mddev_unlock(mddev); > > md_unregister_thread(&mddev->sync_thread); > > + mddev_lock_nointr(mddev); > > if (!test_bit(MD_RECOVERY_INTR, &mddev->recovery) && > > !test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery) && > > mddev->degraded !=3D mddev->raid_disks) { > > -- > > 2.7.4 > >