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Subject[PATCH 1/9] sched/core: add is_kthread() helper
Code checking whether a task is a kthread isn't very consistent. Some
code correctly tests task->flags & PF_THREAD, while other code checks
task->mm (which can be true for a kthread which calls use_mm()).

So that we can clean this up and keep the code easy to follow, let's add
an obvious helper function to test whether a task is a kthread.
Subsequent patches will use this as part of cleaning up and correcting
open-coded tests.

At the same time, let's fix up the kerneldoc for is_idle_task() for
consistency with the new helper, using true/false rather than 0/1, given
the functions return bool.

Signed-off-by: Mark Rutland <>
Cc: Ingo Molnar <>
Cc: Peter Zijlstra <>
include/linux/sched.h | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 9f51932bd543..b7e96409d75f 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1621,13 +1621,24 @@ extern struct task_struct *idle_task(int cpu);
* is_idle_task - is the specified task an idle task?
* @p: the task in question.
- * Return: 1 if @p is an idle task. 0 otherwise.
+ * Return: true if @p is an idle task, false otherwise.
static inline bool is_idle_task(const struct task_struct *p)
return !!(p->flags & PF_IDLE);

+ * is_kthread - is the specified task a kthread
+ * @p: the task in question.
+ *
+ * Return: true if @p is a kthread, false otherwise.
+ */
+static inline bool is_kthread(const struct task_struct *p)
+ return !!(p->flags & PF_KTHREAD);
extern struct task_struct *curr_task(int cpu);
extern void ia64_set_curr_task(int cpu, struct task_struct *p);

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