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Biederman" Cc: Jiazi Li , linux-kernel@vger.kernel.org, "mingzhu.wang" Subject: [PATCH v2] kthread: update comment for __to_kthread Date: Fri, 20 Jun 2025 18:07:56 +0800 Message-ID: <20250620100801.23185-1-jqqlijiazi@gmail.com> X-Mailer: git-send-email 2.49.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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. Suggested-by Eric W . Biederman Signed-off-by: Jiazi Li Signed-off-by: mingzhu.wang Reviewed-by: "Eric W. Biederman" Suggested-by Eric W . Biederman --- Changes in v2: - describe current rules for detect --- --- kernel/kthread.c | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-) diff --git a/kernel/kthread.c b/kernel/kthread.c index 85fc068f0083..0e98b228a8ef 100644 --- a/kernel/kthread.c +++ b/kernel/kthread.c @@ -88,13 +88,12 @@ static inline struct kthread *to_kthread(struct task_st= ruct *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) { --=20 2.49.0