Commit fed307b6 authored Jun 20, 2025 by Jiazi Li Committed by Andrew Morton Jul 09, 2025

kthread: update comment for __to_kthread

With commit 343f4c49 ("kthread: Don't allocate kthread_struct for init
and umh") and commit 753550eb ("fork: Explicitly set PF_KTHREAD"), umh
task no longer have struct kthread and PF_KTHREAD flag.

Update the comment to describe what the current rules are to detect
is something is a kthread.

Link: https://lkml.kernel.org/r/20250620100801.23185-1-jqqlijiazi@gmail.com


Signed-off-by: Jiazi Li <jqqlijiazi@gmail.com>
Signed-off-by: mingzhu.wang <mingzhu.wang@transsion.com>
Suggested-by Eric W . Biederman <ebiederm@xmission.com>
Reviewed-by: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

parent caf728df

kernel/kthread.c

+5 −6

Original line number	Diff line number	Diff line
		@@ -88,13 +88,12 @@ static inline struct kthread to_kthread(struct task_struct k)
		/*
		* Variant of to_kthread() that doesn't assume @p is a kthread.
		*
		* Per construction; when:
		* When "(p->flags & PF_KTHREAD)" is set the task is a kthread and will
		* always remain a kthread. For kthreads p->worker_private always
		* points to a struct kthread. For tasks that are not kthreads
		* p->worker_private is used to point to other things.
		*
		* (p->flags & PF_KTHREAD) && p->worker_private
		*
		* the task is both a kthread and struct kthread is persistent. However
		* PF_KTHREAD on it's own is not, kernel_thread() can exec() (See umh.c and
		* begin_new_exec()).
		* Return NULL for any task that is not a kthread.
		*/
		static inline struct kthread __to_kthread(struct task_struct p)
		{