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Mon, 11 Jan 2021 04:05:05 +0000 Subject: Re: [PATCH v2 bpf-next 4/7] selftests/bpf: sync RCU before unloading bpf_testmod To: Andrii Nakryiko , , , , CC: , Hao Luo , Alexei Starovoitov References: <20210108220930.482456-1-andrii@kernel.org> <20210108220930.482456-5-andrii@kernel.org> From: Yonghong Song Message-ID: <2e7a9040-6b16-bb9f-0cab-73161899e1f1@fb.com> Date: Sun, 10 Jan 2021 20:05:04 -0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 In-Reply-To: <20210108220930.482456-5-andrii@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [2620:10d:c090:400::5:b212] X-ClientProxiedBy: SJ0PR03CA0195.namprd03.prod.outlook.com (2603:10b6:a03:2ef::20) To BYAPR15MB4088.namprd15.prod.outlook.com (2603:10b6:a02:c3::18) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [IPv6:2620:10d:c085:21c1::1158] (2620:10d:c090:400::5:b212) by SJ0PR03CA0195.namprd03.prod.outlook.com (2603:10b6:a03:2ef::20) 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: =?utf-8?B?NEdScEZoUHFscXp4ZDM3MWdNMWg4Vlk0Z09IamdXQUZtWEJzWDVHUVBmUHph?= =?utf-8?B?SjNmbWlvM0xBZG5EZ1E0WDJIR1BCWVhkM0JQTHJ0c1RzTnUzS3RGb0JYZFRQ?= =?utf-8?B?NCtINWZ3Mmc4aDhlUDJZVHVSL0s5UzdSdXhNT3NiNnVTeCtJeUs4NUVFemhT?= =?utf-8?B?MHB0ZXUxdFdMSkptZGttd08vWFpXWGRIdTNLUmNKL3ZUd0w3R1hvTUh6YmZJ?= =?utf-8?B?S3l3OTZoTldLQkJiVUhvVm1YRVhDUGtndGVVanM5aEx0TXR3YzZTUHdtZERE?= =?utf-8?B?b3R5R2VXV0xWb29iTUxXRUhMU0NvTitaZExLZXB6VU81NzVCQUhRY2lwb0hY?= =?utf-8?B?YTJEcU5qZHJGeTFaMmFSY1dzZzltVnk1YjFBSkhrT3FEaXdzajJaekFhT3pR?= =?utf-8?B?SEtGMzhkNksvVHNkaUlIc2dnTm5QNVZNbjNUNjNVQTd1YVJVS1BTU2tzWUNy?= =?utf-8?B?dzl2cjBaUDJaWjQrNmYrSzFCZzB5dis4bnBMTFNLQnZBaldHM3hjOUQ5MVdN?= =?utf-8?B?TmhTME1nelVmU3gwRWtGREwwaWxBSDdGa2dJVHRtS3N4Vmx6K1AyV1RIWEow?= =?utf-8?B?QWtabVBZNnJ3T0NWUkIrUkpSOUZxbHFJeFh5WERZMmtuRk1jWENhVFVVeUVy?= =?utf-8?B?YVorZDFGOGlyY011RU1zRE1NdmRWbHQ5cm5LZEZPZ01MVVZkYWI5Mm5yWFBX?= =?utf-8?B?cGUwbTMrNzQ0TGhlbnNTMXcyWUoxb0J4TTVDcmVYUTI2VEQyTWcxSjdxSmN1?= =?utf-8?B?L2VwOUdZNDBQN0pYa2VFQnNxOTM5dnkrMHBFbUtUUEM4bm8rUjY0RDZFdXZw?= =?utf-8?B?UXVJVjE5Z05lNW5ESFRxTUdRQkx5MnFNeFF4SXBwOTI4WXo1cmxOOUZSV29o?= =?utf-8?B?Rjk5emc1VDNNQmU2REpxa2g4WjN5Q1JmK3prbUh5UWthTWNwdExNcHR0UUVn?= =?utf-8?B?S2ZrS01SVWFyOEw4UFFWQkVuMEhCdEt3Z3ZjZ2NrZ3NpQXZBMUhoaUZYZXNy?= =?utf-8?B?V0RxSHVPcXJ0eXlMd3E5N0hkNy94Kzk0Rzh6eWNtREE1NzZCT3N2c2ViODFK?= =?utf-8?B?ZTBwY3JDS25qSTRrWEkrNFBxbDQrV3hSM2NNVWJVYW4vN1k1dkM5N2V5d2FN?= =?utf-8?B?cm5WZEtlWGJSalAreUJkZC85WktpejNEUVdtQms4dHNOcXVPME1meFJ5RnhW?= =?utf-8?B?NTUwcmRWWEZuc08vcis1NXBSZEFXQzhDM1pPUmVIWEYwa2grdVVTd28rWkRn?= =?utf-8?B?dU1haUJiZUc1WGcxSGNXa1Y5c3dFcVhmbnJlVmFXTmpyeFYwbDZ0ZDJLQ2VN?= =?utf-8?B?b0JYMnRTSEsyVlpBd1pjREE1R2NJVUxqYkV1MHZjUDl0WVAxQUJYb1BtOHFP?= =?utf-8?B?d01KdUVxc3NST3c9PQ==?= X-MS-Exchange-CrossTenant-AuthSource: BYAPR15MB4088.namprd15.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 11 Jan 2021 04:05:05.5250 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2 X-MS-Exchange-CrossTenant-Network-Message-Id: 3294d1ac-4941-4f20-b3a0-08d8b5e613fe X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: uZLNgngcKYR0sEB6pwmIHEmPMCov5oRTAdrmzBMH8A/C6f9uGqfRNv0N5Yr7O/cP X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR15MB3415 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.343,18.0.737 definitions=2021-01-09_13:2021-01-07,2021-01-09 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 mlxscore=0 bulkscore=0 phishscore=0 priorityscore=1501 impostorscore=0 adultscore=0 malwarescore=0 clxscore=1015 suspectscore=0 mlxlogscore=999 spamscore=0 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2101110022 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 1/8/21 2:09 PM, Andrii Nakryiko wrote: > If some of the subtests use module BTFs through ksyms, they will cause > bpf_prog to take a refcount on bpf_testmod module, which will prevent it from > successfully unloading. Module's refcnt is decremented when bpf_prog is freed, > which generally happens in RCU callback. So we need to trigger > syncronize_rcu() in the kernel, which can be achieved nicely with > membarrier(MEMBARRIER_CMD_GLOBAL) syscall. So do that in kernel_sync_rcu() and > make it available to other test inside the test_progs. This synchronize_rcu() > is called before attempting to unload bpf_testmod. > > Fixes: 9f7fa225894c ("selftests/bpf: Add bpf_testmod kernel module for testing") > Suggested-by: Alexei Starovoitov > Signed-off-by: Andrii Nakryiko Acked-by: Yonghong Song