From fed307b67c5bbb17b72c54816cd1bce61c23b4d7 Mon Sep 17 00:00:00 2001 From: Jiazi Li Date: Fri, 20 Jun 2025 18:07:56 +0800 Subject: [PATCH] kthread: update comment for __to_kthread With commit 343f4c49f243 ("kthread: Don't allocate kthread_struct for init and umh") and commit 753550eb0ce1 ("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 Signed-off-by: mingzhu.wang Suggested-by Eric W . Biederman Reviewed-by: "Eric W. Biederman" Cc: Peter Zijlstra Signed-off-by: Andrew Morton --- kernel/kthread.c | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-) diff --git a/kernel/kthread.c b/kernel/kthread.c index 85fc068f0083d..0e98b228a8efd 100644 --- a/kernel/kthread.c +++ b/kernel/kthread.c @@ -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) { -- 2.47.2