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Tue, 9 Jun 2026 22:07:40 +0000 Message-ID: <53959e5a-1e9c-482f-ad4a-595e576c5ba5@intel.com> Date: Tue, 9 Jun 2026 15:07:36 -0700 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net] net: ibm: emac: mal: fix potential system hang in mal_remove() To: Rosen Penev CC: Jakub Kicinski , , Andrew Lunn , "David S. Miller" , "Eric Dumazet" , Paolo Abeni , Jeff Garzik , Roland Dreier , open list References: <20260603230821.5619-1-rosenp@gmail.com> <20260608173638.74da73fe@kernel.org> <4575ae96-2084-4f96-8260-5025fd1ea7f5@intel.com> Content-Language: en-US From: Jacob Keller In-Reply-To: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-ClientProxiedBy: MW4P223CA0009.NAMP223.PROD.OUTLOOK.COM (2603:10b6:303:80::14) To DS0PR11MB7381.namprd11.prod.outlook.com (2603:10b6:8:134::14) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS0PR11MB7381:EE_|DS4PPF64C459891:EE_ X-MS-Office365-Filtering-Correlation-Id: 5a54d1d6-19c3-4c5b-5697-08dec67385a9 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|366016|376014|7416014|18002099003|22082099003|56012099006|11063799006|4143699003; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:DS0PR11MB7381.namprd11.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(1800799024)(366016)(376014)(7416014)(18002099003)(22082099003)(56012099006)(11063799006)(4143699003);DIR:OUT;SFP:1101; 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>>>>>> /* This is *very* bad */ >>>>>> WARN(1, KERN_EMERG >>>>>> "mal%d: commac list is not empty on remove!\n", >>>>>> mal->index); >>>>> >>>>> This one doesn't make sense to me. The list_empty check does a WARN() >>>>> indicating that this is not supposed to happen. >>>>> >>>>> This implies that list_empty should be true, otherwise we'd see a WARN >>>>> every time mal_remove is called. >>>>> >>>>> But in that case, we'd have been calling napi_disable incorrectly in >>>>> most cases where it was previously unsafe according to your claim. >>>>> >>>>> At best, this list_empty check is the wrong way to tell if the napi is >>>>> disabled, at worst, this whole change is pointless. >>>> I asked the AI. It doesn't agree: >>> >>> FTR I agree with Jake, the patch seems to indicate bigger structural >>> issues. Then again I don't want to encourage the stream of patches >>> to this driver so let me just apply this.. >> >> I don't see how applying this discourages the stream of patches? >> Wouldn't that be encouraging? >> >> Or I guess the patch "does" fix something (an extra call to >> napi_disable) and you don't want to encourage a raff of future changes >> to try and fix the overall structural issues? I guess that makes sense. >> >> I still don't follow how this fixes > I don't either. But runtime testing shows it to be an improvement. > If you have runtime testing to back this up, then please ignore my objections :) I think I'd be happier with just the removal of napi_disable from mal_remove(), and not trying to modify the list_empty WARN block, but thats only because it does seem obvious that the existing napi_disable shouldn't be called there (as it was called when the last item was removed from mal->list). > Anyway, it seems various subsystem maintainers want me to fix > pre-existing issues reported by sashiko. > > I also got this feedback previously: > https://lore.kernel.org/netdev/20260107185605.7932173f@kernel.org/