Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Thu, 29 Dec 2022 12:25:19 +0800
From:   Chen Yu <yu.c.chen@intel.com>
To:     <mingo@redhat.com>, <peterz@infradead.org>,
        <juri.lelli@redhat.com>, <vincent.guittot@linaro.org>,
        <linux-kernel@vger.kernel.org>, <pmladek@suse.com>,
        <zyhtheonly@gmail.com>, <zyhtheonly@yeah.net>, <zwp10758@gmail.com>
Subject: Re: [PATCH] sched: print parent comm in sched_show_task()
Message-ID: <Y60WrwuM43HcNVC7@chenyu5-mobl1>
References: <20221227161400.GA7646@didi-ThinkCentre-M930t-N000>
Content-Type: text/plain; charset="us-ascii"
Content-Disposition: inline
In-Reply-To: <20221227161400.GA7646@didi-ThinkCentre-M930t-N000>
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?Z5JkBkxJqdJKR8HQMe3t/AAjAD8B4TYoBiYemTjyvJI9C/T44Oi/Z9PKOGbc?=
 =?us-ascii?Q?MGxpmm3xUciRSzPKySLkrdE4PPGt/WOdIcXQKnJRnw+u7mFFVoxJ338nkVAD?=
 =?us-ascii?Q?Twf6icKyxs98fesTbVOWZ/SLkc77cLD4n8l8J1qa3n+2MXX6Q6U9ZdPDOoc0?=
 =?us-ascii?Q?oH2wVbfbyVCB+ElOZf1Y71/aD5xSQMpDjDCYhUOPPqPGXQngWRRPMC+JQ5Jn?=
 =?us-ascii?Q?/X72HyR50x2Gcpswv7IUoRWoc3f3aUOBVDf5eOTK0jEegQiSQghQ6g4bb1Gb?=
 =?us-ascii?Q?1+t6I41lRibZ02OGj5uzytnzgDEVga3RuJ5hdIPUt3gECuQspWkbnG3x79tx?=
 =?us-ascii?Q?ZkMlXWIjNwZSYJnp80Kj2LlWcwbagoHwbYt1TNVgInuNtbEbKnKzwh+Lnv8N?=
 =?us-ascii?Q?BXLN2kbuyHxH6R7v+1U+PDfukymXI5OBB/7vz+rSM4YDJuU6WvcvNtj5w1MJ?=
 =?us-ascii?Q?OsX+d4Sd2B1hJTnLtqhuLOMyrCmkFj2UuHqnZg99TfZzIimmOUBjav8M8pDo?=
 =?us-ascii?Q?zCdOrJdRAWjv7oinEp/Wzi6zYzBnahxxS4ejbvTgyVsc94LlVjPsZk5jJ5LX?=
 =?us-ascii?Q?FV6eRJu2Jw2Y0++s/loxIJJylk8LtD/DDJ36l3zJLfqLL/x3wHB4CAtlb9w6?=
 =?us-ascii?Q?e8UkTYyfk63rc1KsSUY64aPcUVRb5UX21cuyoXVQWQ9o27Zr/lsSfF2U5z0C?=
 =?us-ascii?Q?xh4Wi8xLSIuMNVI1YS7hVWT9byAv6Jb3AFGM1HtvWSAxMcMkRC7oqHpD2Ifr?=
 =?us-ascii?Q?j2sxKQT8LvTqgWJLOCQ4I75qrasUEcP7FfXEA8V5Y/71+3hUXzkf5roB6MCH?=
 =?us-ascii?Q?uVxwxjfymEbDaiHm0u4RWgYjB0VNNerO88/bY1UIfu2AiMVKMRiSeIkyq24N?=
 =?us-ascii?Q?Wwb43IserZUnr1ljGSFuyalSh8nHyHFVnYagSJ+yJ8+poNXCTTGUEnnh93TC?=
 =?us-ascii?Q?jrhowoZSEkdk3SoU7Hy+4OMM+vLY5rDomrkLVDnRO41uO90I39g+ORAiSRmr?=
 =?us-ascii?Q?/meYjFA5rWXajwh00QZ8kRogu6XgJ40pKXl3QpzTEmLw6VfE3exNqMdmXwV0?=
 =?us-ascii?Q?ZuuqZY3qnrS2tP1UnfelVY+ovkRN/n6genRsGhMEODpfQ6hND925qdD1hB+9?=
 =?us-ascii?Q?4hUqSHe1ZKSjOXkoDkNd1pdmDZIKWjXwBTHW+6xhf6HUMzCUZid7L65D+5f+?=
 =?us-ascii?Q?e5RcL2+gQyAj3OGOC49wS9tsJDAT1BEePwSmEFg1BSGcllKL9VRHFLNIz+v7?=
 =?us-ascii?Q?cmZiPQRN39uh+TS7yoTIJBNWSXAqzPiuTG64BwxP1yfwBtuzwQrzAOQ33qsO?=
 =?us-ascii?Q?7HZKwTNhQjB0dFXVUzokYdCBBZ4lDkHA8rFVo39bVbuH67pFMl+FDW6Vc4lT?=
 =?us-ascii?Q?g8JOOIM6oRYaeQfkivzVSTR8D3TDyj3uyKyxJ+CLiBV4bbW5UBjufedDf9gf?=
 =?us-ascii?Q?f9egoYyl4DqISOwQ+6wX4XT3BeN2BMZBIZapggJV1MfDwCZf7t2iRX0tq4/9?=
 =?us-ascii?Q?RSmOJ24IHKbwSr/p8vgs4e1uiL16YIKiZhSv4op0jRnZ270VItqarFM1cT67?=
 =?us-ascii?Q?/1ZgFIyyYm8eKALIRbU4hy7kb1lwWvcCLOa3HOAJ?=
X-MS-Exchange-CrossTenant-Network-Message-Id: 0e500a29-28a1-4a93-357d-08dae954bc23
X-MS-Exchange-CrossTenant-AuthSource: MN0PR11MB6206.namprd11.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 29 Dec 2022 04:25:37.1773
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: LX/dy8qc8fHBJIO5FhujRCiDg89rrlPicKrc7EK9JgcZQ3WAwCMIb0B6w5KosnBgNphPnv87+k9JIf20hBQhiA==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA2PR11MB4939
X-OriginatorOrg: intel.com
X-Spam-Status: No, score=-7.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,
        DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_HI,
        RCVD_IN_MSPIKE_H3,RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,SPF_NONE
        autolearn=ham autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
        lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On 2022-12-28 at 00:14:00 +0800, Tio Zhang wrote:
> Knowing who the parent is might be useful for debugging.
> For example, we can sometimes resolve kernel hung tasks by stopping
> the person who begins those hung tasks.
> With the parent's name printed in sched_show_task(),
> it might be helpful to let people know which "service" should be operated.
> 
> Signed-off-by: Tio Zhang <tiozhang@didiglobal.com>
> ---
>  kernel/sched/core.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index cb2aa2b54c7a..6f4aef0fed58 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -8854,6 +8854,7 @@ void sched_show_task(struct task_struct *p)
>  {
>  	unsigned long free = 0;
>  	int ppid;
> +	char pcomm[TASK_COMM_LEN];
>  
>  	if (!try_get_task_stack(p))
>  		return;
> @@ -8867,11 +8868,13 @@ void sched_show_task(struct task_struct *p)
>  #endif
>  	ppid = 0;
>  	rcu_read_lock();
> -	if (pid_alive(p))
> +	if (pid_alive(p)) {
>  		ppid = task_pid_nr(rcu_dereference(p->real_parent));
> +		get_task_comm(pcomm, rcu_dereference(p->real_parent));
Maybe struct task_struct *parent = rcu_dereference(p->real_parent);
and use parent directly to get its pid and comm?
Maybe off-topic, what if the parent is a kernel thread/worker? It might have extra
name information such as kthread->full_name or worker->desc according to proc_task_name().

thanks,