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Fri, 10 Jan 2025 18:22:40 +0000 Received: from SN6PR02MB4157.namprd02.prod.outlook.com ([fe80::cedd:1e64:8f61:b9df]) by SN6PR02MB4157.namprd02.prod.outlook.com ([fe80::cedd:1e64:8f61:b9df%4]) with mapi id 15.20.8335.011; Fri, 10 Jan 2025 18:22:40 +0000 From: Michael Kelley To: Herbert Xu CC: Breno Leitao , "saeedm@nvidia.com" , "tariqt@nvidia.com" , "linux-hyperv@vger.kernel.org" , Andrew Morton , Thomas Graf , Tejun Heo , Hao Luo , Josh Don , Barret Rhoden , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: RE: [v2 PATCH] rhashtable: Fix rhashtable_try_insert test Thread-Topic: [v2 PATCH] rhashtable: Fix rhashtable_try_insert test Thread-Index: AQHbY4R22n8scAonrE6mozAIuLs3n7MQTEjQ Date: Fri, 10 Jan 2025 18:22:40 +0000 Message-ID: References: <20241128-scx_lockdep-v1-1-2315b813b36b@debian.org> <20250102-daffy-vanilla-boar-6e1a61@leitao> <20250109-marigold-bandicoot-of-exercise-8ebede@leitao> In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-publictraffictype: Email x-ms-traffictypediagnostic: SN6PR02MB4157:EE_|BN0PR02MB8175:EE_ x-ms-office365-filtering-correlation-id: 97f2b04a-e39b-42e0-f59c-08dd31a3c494 x-microsoft-antispam: BCL:0;ARA:14566002|8062599003|8060799006|461199028|15080799006|19110799003|3412199025|102099032|440099028; 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charset="us-ascii" Content-Transfer-Encoding: quoted-printable Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-OriginatorOrg: outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: SN6PR02MB4157.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-RMS-PersistedConsumerOrg: 00000000-0000-0000-0000-000000000000 X-MS-Exchange-CrossTenant-Network-Message-Id: 97f2b04a-e39b-42e0-f59c-08dd31a3c494 X-MS-Exchange-CrossTenant-rms-persistedconsumerorg: 00000000-0000-0000-0000-000000000000 X-MS-Exchange-CrossTenant-originalarrivaltime: 10 Jan 2025 18:22:40.3605 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 84df9e7f-e9f6-40af-b435-aaaaaaaaaaaa X-MS-Exchange-Transport-CrossTenantHeadersStamped: BN0PR02MB8175 From: Herbert Xu Sent: Friday, January 10, 20= 25 9:24 AM >=20 > On Fri, Jan 10, 2025 at 04:59:28PM +0000, Michael Kelley wrote: > > > > This patch fixes the problem I saw with VMs in the Azure cloud. Thanks= ! >=20 > Sorry, but the test on data is needed after all (it was just > buggy). Otherwise we will break rhlist. So please test this > patch instead. >=20 > ---8<--- > The test on whether rhashtable_insert_one did an insertion relies > on the value returned by rhashtable_lookup_one. Unfortunately that > value is overwritten after rhashtable_insert_one returns. Fix this > by saving the old value. >=20 > Also simplify the test as only data =3D=3D NULL matters. >=20 > Reported-by: Michael Kelley > Fixes: e1d3422c95f0 ("rhashtable: Fix potential deadlock by moving schedu= le_work > outside lock") > Signed-off-by: Herbert Xu >=20 > diff --git a/lib/rhashtable.c b/lib/rhashtable.c > index bf956b85455a..e36b36f3146d 100644 > --- a/lib/rhashtable.c > +++ b/lib/rhashtable.c > @@ -611,17 +611,20 @@ static void *rhashtable_try_insert(struct rhashtabl= e *ht, > const void *key, > new_tbl =3D rht_dereference_rcu(tbl->future_tbl, ht); > data =3D ERR_PTR(-EAGAIN); > } else { > + void *odata; > + > flags =3D rht_lock(tbl, bkt); > data =3D rhashtable_lookup_one(ht, bkt, tbl, > hash, key, obj); > new_tbl =3D rhashtable_insert_one(ht, bkt, tbl, > hash, obj, data); > + odata =3D data; > if (PTR_ERR(new_tbl) !=3D -EEXIST) > data =3D ERR_CAST(new_tbl); >=20 > rht_unlock(tbl, bkt, flags); >=20 > - if (PTR_ERR(data) =3D=3D -ENOENT && !new_tbl) { > + if (odata && !new_tbl) { > atomic_inc(&ht->nelems); > if (rht_grow_above_75(ht, tbl)) > schedule_work(&ht->run_work); This patch passes my tests. I'm doing a narrow test to verify that the boot failure when opening the Mellanox NIC is no longer occurring. I also unloaded/reloaded the mlx5 driver a couple of times. For good measure, I then did a full Linux kernel build, and all is good. My testing does not broadly verify correct operation of rhashtable except as it gets exercised implicitly by these basic tests. Michael