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Tue, 9 Jun 2026 01:13:15 +0000 Message-ID: Date: Mon, 8 Jun 2026 18:13:16 -0700 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net] net: ibm: emac: mal: fix potential system hang in mal_remove() To: Jakub Kicinski , Rosen Penev CC: , 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> Content-Language: en-US From: Jacob Keller In-Reply-To: <20260608173638.74da73fe@kernel.org> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-ClientProxiedBy: MW4PR04CA0292.namprd04.prod.outlook.com (2603:10b6:303:89::27) To CY8PR11MB7364.namprd11.prod.outlook.com (2603:10b6:930:87::14) Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CY8PR11MB7364:EE_|BN9PR11MB5290:EE_ X-MS-Office365-Filtering-Correlation-Id: 07ac29d2-eea5-4495-c0bf-08dec5c44898 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|366016|7416014|376014|18002099003|22082099003|11063799006|4143699003|56012099006; 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:CY8PR11MB7364.namprd11.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(1800799024)(366016)(7416014)(376014)(18002099003)(22082099003)(11063799006)(4143699003)(56012099006);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? I guess you don't want to encourage a raff of future changes to try and fix the overall structural issues? and instead accept the small fix here? How plausible is it that existing users have *never* called mal_remove?? If the list_empty check is to be believed, we shouldn't be getting to mal_remove with list_empty being false... (since that implies that the co-macs are still registered) and users would see the WARN. But if we are getting here with list_empty, we stall indefinitely. Ultimately it is that which is bothering me. It feels like a classic "how did this *ever* work???" scenario...