linux-kernel - [PATCH 02/11] kernel: Allow a kernel thread's name to be set in copy

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Message-Id: <20230310220332.5309-3-michael.christie@oracle.com>
Date:   Fri, 10 Mar 2023 16:03:23 -0600
From:   Mike Christie <michael.christie@...cle.com>
To:     hch@...radead.org, stefanha@...hat.com, jasowang@...hat.com,
        mst@...hat.com, sgarzare@...hat.com,
        virtualization@...ts.linux-foundation.org, brauner@...nel.org,
        ebiederm@...ssion.com, torvalds@...ux-foundation.org,
        konrad.wilk@...cle.com, linux-kernel@...r.kernel.org
Cc:     Mike Christie <michael.christie@...cle.com>
Subject: [PATCH 02/11] kernel: Allow a kernel thread's name to be set in copy_process

This patch allows kernel users to pass in the thread name so it can be
set during creation instead of having to use set_task_comm after the
thread is created.

Signed-off-by: Mike Christie <michael.christie@...cle.com>
---
 include/linux/sched/task.h | 4 +++-
 init/main.c                | 2 +-
 kernel/fork.c              | 7 ++++++-
 kernel/kthread.c           | 3 ++-
 4 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h
index 357e0068497c..32c9f01af0a6 100644
--- a/include/linux/sched/task.h
+++ b/include/linux/sched/task.h
@@ -23,6 +23,7 @@ struct kernel_clone_args {
 	int __user *pidfd;
 	int __user *child_tid;
 	int __user *parent_tid;
+	const char *name;
 	int exit_signal;
 	unsigned long stack;
 	unsigned long stack_size;
@@ -91,7 +92,8 @@ extern void exit_itimers(struct task_struct *);
 extern pid_t kernel_clone(struct kernel_clone_args *kargs);
 struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node);
 struct task_struct *fork_idle(int);
-extern pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags);
+extern pid_t kernel_thread(int (*fn)(void *), void *arg, const char *name,
+			    unsigned long flags);
 extern pid_t user_mode_thread(int (*fn)(void *), void *arg, unsigned long flags);
 extern long kernel_wait4(pid_t, int __user *, int, struct rusage *);
 int kernel_wait(pid_t pid, int *stat);
diff --git a/init/main.c b/init/main.c
index e1c3911d7c70..9dc816aa904f 100644
--- a/init/main.c
+++ b/init/main.c
@@ -707,7 +707,7 @@ noinline void __ref rest_init(void)
 	rcu_read_unlock();
 
 	numa_default_policy();
-	pid = kernel_thread(kthreadd, NULL, CLONE_FS | CLONE_FILES);
+	pid = kernel_thread(kthreadd, NULL, NULL, CLONE_FS | CLONE_FILES);
 	rcu_read_lock();
 	kthreadd_task = find_task_by_pid_ns(pid, &init_pid_ns);
 	rcu_read_unlock();
diff --git a/kernel/fork.c b/kernel/fork.c
index 9f7fe3541897..cb8f85c88c75 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2109,6 +2109,9 @@ static __latent_entropy struct task_struct *copy_process(
 		siginitsetinv(&p->blocked, sigmask(SIGKILL)|sigmask(SIGSTOP));
 	}
 
+	if (args->name)
+		strscpy_pad(p->comm, args->name, sizeof(p->comm));
+
 	p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? args->child_tid : NULL;
 	/*
 	 * Clear TID on mm_release()?
@@ -2727,7 +2730,8 @@ pid_t kernel_clone(struct kernel_clone_args *args)
 /*
  * Create a kernel thread.
  */
-pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
+pid_t kernel_thread(int (*fn)(void *), void *arg, const char *name,
+		    unsigned long flags)
 {
 	struct kernel_clone_args args = {
 		.flags		= ((lower_32_bits(flags) | CLONE_VM |
@@ -2735,6 +2739,7 @@ pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
 		.exit_signal	= (lower_32_bits(flags) & CSIGNAL),
 		.fn		= fn,
 		.fn_arg		= arg,
+		.name		= name,
 		.kthread	= 1,
 	};
 
diff --git a/kernel/kthread.c b/kernel/kthread.c
index f97fd01a2932..63574cee925e 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -396,7 +396,8 @@ static void create_kthread(struct kthread_create_info *create)
 	current->pref_node_fork = create->node;
 #endif
 	/* We want our own signal handler (we take no signals by default). */
-	pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD);
+	pid = kernel_thread(kthread, create, NULL,
+			    CLONE_FS | CLONE_FILES | SIGCHLD);
 	if (pid < 0) {
 		/* Release the structure when caller killed by a fatal signal. */
 		struct completion *done = xchg(&create->done, NULL);
-- 
2.25.1