From nobody Sat Dec 4 00:25:48 2021 X-Original-To: freebsd-stable@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id DAAEA18D1916 for ; Sat, 4 Dec 2021 00:26:06 +0000 (UTC) (envelope-from asomers@gmail.com) Received: from mail-oo1-f45.google.com (mail-oo1-f45.google.com [209.85.161.45]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (2048 bits) client-digest SHA256) (Client CN "smtp.gmail.com", Issuer "GTS CA 1D4" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4J5Vq25hw6z4qg4 for ; Sat, 4 Dec 2021 00:26:06 +0000 (UTC) (envelope-from asomers@gmail.com) Received: by mail-oo1-f45.google.com with SMTP id p2-20020a4adfc2000000b002c2676904fdso2534209ood.13 for ; Fri, 03 Dec 2021 16:26:06 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=Nc16PRQ/wTbIa+Bn30W4OXrhl7zlpk5Mqel61HNqLwk=; b=6sDpsTa2lRgmd5vVnkaImokjjX2V1QH/VWD/h/A1EgaTbszBngn2oGcQItFYTRlqdZ SUiiuug/shMFJfYgyJwpI8JiqEMRCzgbjOe+KEP7JwQZfmgen53u4lYUKOPvGSAR5SW4 ZK8U1yqXlmIOgRFaz7PsUaLWPF31ugdal/vucQOoCNSw0jxYN2rNT09blC0l3iU21Syu ILZP+5UINazCiadVnUY1FXhcNZb/FZbSPfm0w3yrWNrIumypcdFkeeiblcudMgAGE43R UfgNmxUtABh7iqSWGs+vo9Sie9+USZJG06FzAnDH+bakEFrHqa4Z9ZRJ7p+ayYZmSSC6 TV+A== X-Gm-Message-State: AOAM533/eJBMXqsHHPakn0ScBScSJmiNHmphzTanb8Pc53TeiiWcfA+D dqguknbSSj5+7XiUzyUtz4GRHTqPZmsFfCi59HhdliJD X-Google-Smtp-Source: ABdhPJxwpu6RLen28pqCi0q/r0p2eJxpv9D81Mm5A0ZPK432DSjnHq0GSkg5ISkd1TGvv9nvkRbuyM4rKzQmBB+Pe5o= X-Received: by 2002:a4a:6215:: with SMTP id x21mr14654316ooc.16.1638577560177; Fri, 03 Dec 2021 16:26:00 -0800 (PST) List-Id: Production branch of FreeBSD source code List-Archive: https://lists.freebsd.org/archives/freebsd-stable List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-freebsd-stable@freebsd.org X-BeenThere: freebsd-stable@freebsd.org MIME-Version: 1.0 References: In-Reply-To: From: Alan Somers Date: Fri, 3 Dec 2021 17:25:48 -0700 Message-ID: Subject: Re: ZFS deadlocks triggered by HDD timeouts To: Warner Losh Cc: FreeBSD Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: 4J5Vq25hw6z4qg4 X-Spamd-Bar: ---- Authentication-Results: mx1.freebsd.org; none X-Spamd-Result: default: False [-4.00 / 15.00]; REPLY(-4.00)[] X-ThisMailContainsUnwantedMimeParts: N On Fri, Dec 3, 2021 at 5:19 PM Warner Losh wrote: > > Hey Alan, > > On Fri, Dec 3, 2021 at 8:38 AM Alan Somers wrote: >> >> On Wed, Dec 1, 2021 at 3:48 PM Warner Losh wrote: >> > >> > >> > >> > On Wed, Dec 1, 2021, 3:36 PM Alan Somers wrote: >> >> >> >> On Wed, Dec 1, 2021 at 2:46 PM Warner Losh wrote: >> >> > >> >> > >> >> > >> >> > >> >> > On Wed, Dec 1, 2021, 2:36 PM Alan Somers wrote: >> >> >> >> >> >> On Wed, Dec 1, 2021 at 1:56 PM Warner Losh wrote: >> >> >> > >> >> >> > >> >> >> > >> >> >> > On Wed, Dec 1, 2021 at 1:47 PM Alan Somers wrote: >> >> >> >> >> >> >> >> On Wed, Dec 1, 2021 at 1:37 PM Warner Losh wrote: >> >> >> >> > >> >> >> >> > >> >> >> >> > >> >> >> >> > On Wed, Dec 1, 2021 at 1:28 PM Alan Somers wrote: >> >> >> >> >> >> >> >> >> >> On Wed, Dec 1, 2021 at 11:25 AM Warner Losh wrote: >> >> >> >> >> > >> >> >> >> >> > >> >> >> >> >> > >> >> >> >> >> > On Wed, Dec 1, 2021, 11:16 AM Alan Somers wrote: >> >> >> >> >> >> >> >> >> >> >> >> On a stable/13 build from 16-Sep-2021 I see frequent ZFS deadlocks >> >> >> >> >> >> triggered by HDD timeouts. The timeouts are probably caused by >> >> >> >> >> >> genuine hardware faults, but they didn't lead to deadlocks in >> >> >> >> >> >> 12.2-RELEASE or 13.0-RELEASE. Unfortunately I don't have much >> >> >> >> >> >> additional information. ZFS's stack traces aren't very informative, >> >> >> >> >> >> and dmesg doesn't show anything besides the usual information about >> >> >> >> >> >> the disk timeout. I don't see anything obviously related in the >> >> >> >> >> >> commit history for that time range, either. >> >> >> >> >> >> >> >> >> >> >> >> Has anybody else observed this phenomenon? Or does anybody have a >> >> >> >> >> >> good way to deliberately inject timeouts? CAM makes it easy enough to >> >> >> >> >> >> inject an error, but not a timeout. If it did, then I could bisect >> >> >> >> >> >> the problem. As it is I can only reproduce it on production servers. >> >> >> >> >> > >> >> >> >> >> > >> >> >> >> >> > What SIM? Timeouts are tricky because they have many sources, some of which are nonlocal... >> >> >> >> >> > >> >> >> >> >> > Warner >> >> >> >> >> >> >> >> >> >> mpr(4) >> >> >> >> > >> >> >> >> > >> >> >> >> > Is this just a single drive that's acting up, or is the controller initialized as part of the error recovery? >> >> >> >> >> >> >> >> I'm not doing anything fancy with mprutil or sas3flash, if that's what >> >> >> >> you're asking. >> >> >> > >> >> >> > >> >> >> > No. I'm asking if you've enabled debugging on the recovery messages and see that we enter any kind of >> >> >> > controller reset when the timeouts occur. >> >> >> >> >> >> No. My CAM setup is the default except that I enabled CAM_IO_STATS >> >> >> and changed the following two sysctls: >> >> >> kern.cam.da.retry_count=2 >> >> >> kern.cam.da.default_timeout=10 >> >> >> >> >> >> >> >> >> > >> >> >> >> >> >> >> >> > If a single drive, >> >> >> >> > are there multiple timeouts that happen at the same time such that we timeout a request while we're waiting for >> >> >> >> > the abort command we send to the firmware to be acknowledged? >> >> >> >> >> >> >> >> I don't know. >> >> >> > >> >> >> > >> >> >> > OK. >> >> >> > >> >> >> >> >> >> >> >> > Would you be able to run a kgdb script to see >> >> >> >> > if you're hitting a situation that I fixed in mpr that would cause I/O to never complete in this rather odd circumstance? >> >> >> >> > If you can, and if it is, then there's a change I can MFC :). >> >> >> >> >> >> >> >> Possibly. When would I run this kgdb script? Before ZFS locks up, >> >> >> >> after, or while the problematic timeout happens? >> >> >> > >> >> >> > >> >> >> > After the timeouts. I've been doing 'kgdb' followed by 'source mpr-hang.gdb' to run this. >> >> >> > >> >> >> > What you are looking for is anything with a qfrozen_cnt > 0.. The script is imperfect and racy >> >> >> > with normal operations (but not in a bad way), so you may need to run it a couple of times >> >> >> > to get consistent data. On my systems, there'd be one or two devices with a frozen count > 1 >> >> >> > and no I/O happened on those drives and processes hung. That might not be any different than >> >> >> > a deadlock :) >> >> >> > >> >> >> > Warner >> >> >> > >> >> >> > P.S. here's the mpr-hang.gdb script. Not sure if I can make an attachment survive the mailing lists :) >> >> >> >> >> >> Thanks, I'll try that. If this is the problem, do you have any idea >> >> >> why it wouldn't happen on 12.2-RELEASE (I haven't seen it on >> >> >> 13.0-RELEASE, but maybe I just don't have enough runtime on that >> >> >> version). >> >> > >> >> > >> >> > 9781c28c6d63 was merged to stable/13 as a996b55ab34c on Sept 2nd. I fixed a bug >> >> > with that version in current as a8837c77efd0, but haven't merged it. I kinda expect that >> >> > this might be the cause of the problem. But in Netflix's fleet we've seen this maybe a >> >> > couple of times a week over many thousands of machines, so I've been a little cautious >> >> > in merging it to make sure that it's really fixed. So far, the jury is out. >> >> > >> >> > Warner >> >> >> >> Well, I'm experiencing this error much more frequently than you then. >> >> I've seen it on about 10% of similarly-configured servers and they've >> >> only been running that release for 1 week. >> > >> > >> > You can run my script soon then to see if it's the same thing. >> > >> > Warner >> > >> >> -Alan >> >> That confirms it. I hit the deadlock again, and qfrozen_cnt was >> between 1 and 3 for four devices: two da devices (we use multipath) >> and their accompanying pass devices. So I should try merging >> a8837c77efd0 next? > > > Yes. I'd planned on merging it this weekend, but if you wanted a jump > on me, that's the next step. > > Warner It merged without conflict, and I'm testing it now. But without a way to inject timeouts I can't tell whether it's working. -Alan