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Fri, 7 Oct 2016 13:27:35 +0000 To: Jonathan Morton 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> CC: From: Kevin Darbyshire-Bryant Message-ID: Date: Fri, 7 Oct 2016 14:27:32 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.3.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [151.229.93.35] X-ClientProxiedBy: DB5PR0201CA0022.eurprd02.prod.outlook.com (10.164.231.160) To AMSPR07MB115.eurprd07.prod.outlook.com (10.242.81.144) X-MS-Office365-Filtering-Correlation-Id: 8d647049-aea1-4afb-a420-08d3eeb5b331 X-Microsoft-Exchange-Diagnostics: 1; AMSPR07MB115; 2:lsLZVGHqp4dKouyjAzJFXyZjjjVIr7+iKKEQ/eFgp2b9Nj8uvC3/mKEasu9ibojvo1d8P71U/HxaYl07ShuWkFGoCI30SgaFEm1kErLYufdjAlHApbiR0tQDeZK2dYgFOmxZNySnAXtyU/EeDhMCJSrG2yjBx2HjKV82w4BntqjWl9y1KjVxn06O5ENlVcWweX6FAJRF/drbRKiaYXfAPQ==; 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I really >>> must try again when I've more time to get proper access. >> >> I’m having trouble reproducing it here. I know one of my boxes >> froze the very first time I loaded it, but it’s been running fine >> ever since. Another machine is currently refusing to insert the >> module, claiming a wrong exec format. It’s all a bit bizarre. >> >> 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’s 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’ll increment > the deficit by a random value, but that usually won’t prevent traffic > flowing. > > The lookup is indexed on the host refcnt, which I’m using as the > count of flows attached to that host. It seems likely that it isn’t > being maintained correctly in all cases, so it can wrap around past > zero very soon after being attached, without needing much traffic. > > I’ll try to fix that, and put a sanity check in as well to be > certain. It's now ok...so far :-)