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Mon, 11 Jan 2021 18:56:57 +0000 Date: Mon, 11 Jan 2021 10:56:50 -0800 From: Martin KaFai Lau To: Song Liu CC: , , , , , , , , , , , , kernel test robot Subject: Re: [PATCH bpf-next 1/4] bpf: enable task local storage for tracing programs Message-ID: <20210111185650.hsvfpoqmqc2mj7ci@kafai-mbp.dhcp.thefacebook.com> References: <20210108231950.3844417-1-songliubraving@fb.com> <20210108231950.3844417-2-songliubraving@fb.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210108231950.3844417-2-songliubraving@fb.com> X-Originating-IP: [2620:10d:c090:400::5:e2df] X-ClientProxiedBy: MWHPR15CA0069.namprd15.prod.outlook.com (2603:10b6:301:4c::31) To BY5PR15MB3571.namprd15.prod.outlook.com (2603:10b6:a03:1f6::32) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from kafai-mbp.dhcp.thefacebook.com (2620:10d:c090:400::5:e2df) by MWHPR15CA0069.namprd15.prod.outlook.com (2603:10b6:301:4c::31) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3742.6 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: =?us-ascii?Q?Fc+EJRER8/wxShLu+Wa1ddNEixpWPBbQGl5wTqrm76o82bAhK/C9wBr8N8fe?= =?us-ascii?Q?zjduXwEuxHQfXiM+gVoziIdeR11lEmXgsLT4K4T5Nl87zpPLEIDBhW4ssgKW?= =?us-ascii?Q?1wRGY5/72YPoJJNH6u2Iy4lJGdLZp5bu2xI70Y59y4urJFGbuITEYd+T07tY?= =?us-ascii?Q?XqFuG1xW0CCVoZXfc5yiDZ320TubeSPU7wOT9P7qs1ZyFxmkx77ELUu1CIWl?= =?us-ascii?Q?HwTx4cPGhjE59hCtDhFnj70nL/cXlOsJljdNN3LYwYBbCWCgqm1vYIyc1tq2?= =?us-ascii?Q?LlUAUJRTOL/u3jc7nBa0iGKYAa97nou728cGchxXaNbGF2zeMR0zgI/GQ9cD?= =?us-ascii?Q?y/iyIidwksNnjM36o7IUCYdRWosJ02YHFZZBFJgRJfU2vmK+BsAZZPzhbUdm?= =?us-ascii?Q?6IEuCw+mGiZxoP+20WM5SHidzkE+PxItQVh9Hljve0X6I4JabFodBdDSxgpL?= =?us-ascii?Q?VWB4nFGiIk98/lieNrTHvirfbaaImlQwvreQmtjr6p93IVuAwTGrPLPSwPsg?= =?us-ascii?Q?bLaWcsngvyNgCVQKwLipuxx8ws7IEEshfGnUcnGgbY8OvN9qjlLB17FN0uOx?= =?us-ascii?Q?zMoQP9xz4O7wY+McJWh+a7v9EqgyuUSY0jao6QzRbjaJK78e4Pz00LCIgKQ1?= =?us-ascii?Q?WW5DSRtEW2ZtfpBOZeOWXzdph49r2gYr3ptzO+rmWO0UB+eWXJYRlluApCIF?= =?us-ascii?Q?tcGnj9SmFlRq3HAmWoa6YVOl/ymqHkgzI9b6PXA9aIb8hdj+9NVtF43vv5wc?= =?us-ascii?Q?Ghg7ti0CMqHVNfN+U9XXE9/G6Y7yy1hvpn1/7APT9yia8dTbpyetVmBPQPfz?= =?us-ascii?Q?7p4wI9hHcyNLQAcpLpxNLGtuGRIjmILGDWK1Er2iIMQFqT0hXj1kiDgBcr8Y?= =?us-ascii?Q?TdYzQRNCxJZOb8aYea4+L7+hpXiYxyNmCj2Au2UIyrgK3YglOeP+MQPw266N?= =?us-ascii?Q?IKxQbtvlxRuMraFzZcUkpN8XAkIrK76Wz0QgABoli3Sop0y8Y1H6vxTCpKhg?= =?us-ascii?Q?L+g1U1iy+wb6bqNgrIaQrqV4yQ=3D=3D?= X-MS-Exchange-CrossTenant-AuthSource: BY5PR15MB3571.namprd15.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 11 Jan 2021 18:56:57.2677 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2 X-MS-Exchange-CrossTenant-Network-Message-Id: 9fb7c08d-53d4-415e-1f0d-08d8b662ab8b X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: g6NcQSd4NTg+DJ9Nc3Y5dtIMIgAuv6rsoQCK/UJFwBzvyKmOTS7WqJ332KXi1ZqO X-MS-Exchange-Transport-CrossTenantHeadersStamped: BY5PR15MB3618 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.343,18.0.737 definitions=2021-01-11_29:2021-01-11,2021-01-11 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 mlxlogscore=999 malwarescore=0 lowpriorityscore=0 bulkscore=0 suspectscore=0 adultscore=0 impostorscore=0 clxscore=1011 mlxscore=0 priorityscore=1501 spamscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2101110104 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Fri, Jan 08, 2021 at 03:19:47PM -0800, Song Liu wrote: [ ... ] > diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c > index dd5aedee99e73..9bd47ad2b26f1 100644 > --- a/kernel/bpf/bpf_local_storage.c > +++ b/kernel/bpf/bpf_local_storage.c > @@ -140,17 +140,18 @@ static void __bpf_selem_unlink_storage(struct bpf_local_storage_elem *selem) > { > struct bpf_local_storage *local_storage; > bool free_local_storage = false; > + unsigned long flags; > > if (unlikely(!selem_linked_to_storage(selem))) > /* selem has already been unlinked from sk */ > return; > > local_storage = rcu_dereference(selem->local_storage); > - raw_spin_lock_bh(&local_storage->lock); > + raw_spin_lock_irqsave(&local_storage->lock, flags); It will be useful to have a few words in commit message on this change for future reference purpose. Please also remove the in_irq() check from bpf_sk_storage.c to avoid confusion in the future. It probably should be in a separate patch. [ ... ] > diff --git a/kernel/bpf/bpf_task_storage.c b/kernel/bpf/bpf_task_storage.c > index 4ef1959a78f27..f654b56907b69 100644 > diff --git a/kernel/fork.c b/kernel/fork.c > index 7425b3224891d..3d65c8ebfd594 100644 [ ... ] > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -96,6 +96,7 @@ > #include > #include > #include > +#include > > #include > #include > @@ -734,6 +735,7 @@ void __put_task_struct(struct task_struct *tsk) > cgroup_free(tsk); > task_numa_free(tsk, true); > security_task_free(tsk); > + bpf_task_storage_free(tsk); > exit_creds(tsk); If exit_creds() is traced by a bpf and this bpf is doing bpf_task_storage_get(..., BPF_LOCAL_STORAGE_GET_F_CREATE), new task storage will be created after bpf_task_storage_free(). I recalled there was an earlier discussion with KP and KP mentioned BPF_LSM will not be called with a task that is going away. It seems enabling bpf task storage in bpf tracing will break this assumption and needs to be addressed?