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Miller" , David Ahern , Eric Dumazet , Simon Horman , David Ahern , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, Jakub Kicinski , Breno Leitao References: <20241108-ipmr_rcu-v2-1-c718998e209b@debian.org> <20241113191023.401fad6b@kernel.org> <20241114-ancient-piquant-ibex-28a70b@leitao> <20241114070308.79021413@kernel.org> <20241115-frisky-mahogany-mouflon-19fc5b@leitao> <20241115080031.6e6e15ff@kernel.org> <9cdf4969-8422-4cda-b1d0-35a57a1fe233@nokia.com> <9837c682-72a0-428e-81ab-b42f201b3c71@redhat.com> <7003f775-7389-41ed-95e5-1e0e07f3f6fb@redhat.com> Content-Language: en-US From: Stefan Wiehler Organization: Nokia In-Reply-To: <7003f775-7389-41ed-95e5-1e0e07f3f6fb@redhat.com> Content-Type: text/plain; charset=UTF-8 X-ClientProxiedBy: FR3P281CA0105.DEUP281.PROD.OUTLOOK.COM (2603:10a6:d10:a1::6) To VI1PR07MB9706.eurprd07.prod.outlook.com (2603:10a6:800:1d2::12) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: 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Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 21 Nov 2024 14:47:55.3188 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 5d471751-9675-428d-917b-70f44f9630b0 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: osRkWmdH+psPZrbUT3DJbzgatpaqyVOHe93YwSs5iSq0iW10wWrRE6wKAU73y5BipaADKLyFElp/fHqRJubVF0S6TH99Pwyg8XAcAjCFhwQ= X-MS-Exchange-Transport-CrossTenantHeadersStamped: DB9PR07MB7945 > On 11/15/24 17:55, Paolo Abeni wrote: >> On 11/15/24 17:07, Stefan Wiehler wrote: >>>> On Fri, 15 Nov 2024 01:16:27 -0800 Breno Leitao wrote: >>>>> This one seems to be discussed in the following thread already. >>>>> >>>>> https://lore.kernel.org/all/20241017174109.85717-1-stefan.wiehler@nokia.com/ >>>> >>>> That's why it rung a bell.. >>>> Stefan, are you planning to continue with the series? >>> >>> Yes, sorry for the delay, went on vacation and was busy with other tasks, but >>> next week I plan to continue (i.e. refactor using refcount_t). >> >> I forgot about that series and spent a little time investigating the >> scenario. >> >> I think we don't need a refcount: the tables are freed only at netns >> cleanup time, so the netns refcount is enough to guarantee that the >> tables are not deleted when escaping the RCU section. >> >> Some debug assertions could help clarify, document and make the schema >> more robust to later change. >> >> Side note, I think we need to drop the RCU lock moved by: >> >> https://lore.kernel.org/all/20241017174109.85717-2-stefan.wiehler@nokia.com/ >> >> as the seqfile core can call blocking functions - alloc(GFP_KERNEL) - >> between ->start() and ->stop(). >> >> The issue is pre-existent to that patch, and even to the patch >> introducing the original RCU() - the old read_lock() created an illegal >> atomic scope - but I think we should address it while touching this code. > > @Stefan: are you ok if I go ahead with this work, or do you prefer > finish it yourself? Please go ahead, I have neither the expertise in the net subsystem nor the time to ramp-up (since this is just a side finding for us right now) to proceed with your proposal. I'll follow the discussion though and hope to learn something along the way! Kind regards, Stefan