From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf0-x22b.google.com (mail-lf0-x22b.google.com [IPv6:2a00:1450:4010:c07::22b]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id ADC743B25E for ; Wed, 5 Oct 2016 14:53:03 -0400 (EDT) Received: by mail-lf0-x22b.google.com with SMTP id b75so88660911lfg.3 for ; Wed, 05 Oct 2016 11:53:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=MhAJs9xkRX39SwncDT2dB7fRFceR3N01xY2atVkXSmQ=; b=QQzWBjz77hAEbSilHPNLIc/ZoP8Dr+Wyx9QE8lJiwI1+mgyDNBoZIosbQPxcPdmHe+ cQvoIVjSscl/CovG3MAjJmHmkYr31E1Z2PnmOrgpgkzDT3Z/MynWA4uEXffFTXfECgYP PeJ9k24ApZpB/2M0ajZuEepPO042y1M49NVU399sbT4t26SRuCPXjVfC8nPaZ88MVqMb XxfdGWHOo9dl93TOfmGriYB4AO0EQnq36zJhf7PCiriQZOBfqsbldzRER84JakWdUJ6e heIaHLQyrYrVj2xGAcqX6YcQRdJN0elP+W3cq9Q5SL2+cec1xhCRkkd8JVYDqqAMEMM1 wayw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=MhAJs9xkRX39SwncDT2dB7fRFceR3N01xY2atVkXSmQ=; b=ZdB7aXGD0+68Q22WvqWjUK1Cyts410MVLcMD89w1DaHWEpl8LSCKcTMmh1rXXnIsva dzE1GmITtzZzM7aR8nDu33WXYGuK7BW8diIljewR4SQzcSD5lLXT904CspRIVPg7v3GC IJadFKS1F9AoL8Hgu5XiL+wx1615EDIbktG0UMhBoktEzsqoXzDPmEiluq/dhag5uubS TgumkQM9TM2pM8AJwElW7S1J4wqqns0IWyTXgRKVAZdEztTalhFWFg4nN9591/zJhAVA 7UdNjXwcmY/wShvIXGzWpdCv3IHVxgYD41TeyWZ9MrqXBzXeBI4CcL5ie98j1ggTN+A8 P0/Q== X-Gm-Message-State: AA6/9RmrnLrCIEMjWPQJutv8sjXb+wqPfpo6CdbN0rKbZKE3gtSSTAGNKy6YVdlX68lBCw== X-Received: by 10.25.25.18 with SMTP id 18mr4121744lfz.49.1475693582331; Wed, 05 Oct 2016 11:53:02 -0700 (PDT) Received: from [192.168.100.13] (37-33-90-35.bb.dnainternet.fi. [37.33.90.35]) by smtp.gmail.com with ESMTPSA id 204sm1897667ljf.5.2016.10.05.11.53.01 (version=TLS1 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Wed, 05 Oct 2016 11:53:01 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 9.3 \(3124\)) From: Jonathan Morton In-Reply-To: <541238C5-6AAD-4B70-B58E-4831F9FE20A3@gmail.com> Date: Wed, 5 Oct 2016 21:53:00 +0300 Cc: cake@lists.bufferbloat.net Content-Transfer-Encoding: quoted-printable Message-Id: References: <70363372-13a0-a88f-840e-b8e10c685ed7@darbyshire-bryant.me.uk> <451e7412-2f27-1421-1bd6-ac2ef45f4cd8@darbyshire-bryant.me.uk> <541238C5-6AAD-4B70-B58E-4831F9FE20A3@gmail.com> To: Kevin Darbyshire-Bryant X-Mailer: Apple Mail (2.3124) Subject: Re: [Cake] BUG_ON vs WARN_ON X-BeenThere: cake@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: Cake - FQ_codel the next generation List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 05 Oct 2016 18:53:03 -0000 >> I wonder what it was that caused yesterday's issues? I really must = try again when I've more time to get proper access. >=20 > I=E2=80=99m having trouble reproducing it here. I know one of my = boxes froze the very first time I loaded it, but it=E2=80=99s been = running fine ever since. Another machine is currently refusing to = insert the module, claiming a wrong exec format. It=E2=80=99s all a bit = bizarre. >=20 > I do have a few more avenues of enquiry to explore, though. Aha - I managed to capture a kernel panic, which appears to trace to the = lookup in the accelerator array. It=E2=80=99s a read-only access, so it = only panics if it hits unpaged memory, rather than corrupting anything. = Of course, if it reads outside the array, it=E2=80=99ll increment the = deficit by a random value, but that usually won=E2=80=99t prevent = traffic flowing. The lookup is indexed on the host refcnt, which I=E2=80=99m using as the = count of flows attached to that host. It seems likely that it isn=E2=80=99= t being maintained correctly in all cases, so it can wrap around past = zero very soon after being attached, without needing much traffic. I=E2=80=99ll try to fix that, and put a sanity check in as well to be = certain. - Jonathan Morton