linux-kernel - [PATCH 5/5] kernel/kthread: show a warning if kthread's comm is still trucated

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Date:   Wed, 29 Sep 2021 11:50:36 +0000
From:   Yafang Shao <laoar.shao@...il.com>
To:     akpm@...ux-foundation.org, pmladek@...e.com, peterz@...radead.org,
        valentin.schneider@....com, keescook@...omium.org,
        mathieu.desnoyers@...icios.com, qiang.zhang@...driver.com,
        robdclark@...omium.org, viro@...iv.linux.org.uk,
        christian@...uner.io, dietmar.eggemann@....com
Cc:     linux-kernel@...r.kernel.org, Yafang Shao <laoar.shao@...il.com>
Subject: [PATCH 5/5] kernel/kthread: show a warning if kthread's comm is still trucated

Show a warning if the ktrhead's comm is still trucated. Below is the
result of my test case -

__kthread_create_on_node:410: comm of pid 14 is truncated from "I-am-a-kthread-with-long-name" to "I-am-a-kthread-with-lon"

Signed-off-by: Yafang Shao <laoar.shao@...il.com>
---
 kernel/kthread.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/kernel/kthread.c b/kernel/kthread.c
index 6def951c605a..aa093f1f423a 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -404,7 +404,11 @@ struct task_struct *__kthread_create_on_node(int (*threadfn)(void *data),
 		 * task is already visible to other tasks, so updating
 		 * COMM must be protected.
 		 */
-		vsnprintf(name, sizeof(name), namefmt, args);
+		if (vsnprintf(name, KTHREAD_COMM_LEN, namefmt, args) >=
+		    KTHREAD_COMM_LEN)
+			pr_warn("%s:%d: comm of pid %d is truncated from \"%s\" to \"%s\"\n",
+				__func__, __LINE__, task->pid, namefmt, name);
+
 		set_task_comm(task, name);
 		/*
 		 * root may have changed our (kthreadd's) priority or CPU mask.
-- 
2.17.1