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Subject[PATCH v10 2/8] cpu/hotplug: Move idle_thread_get() to <linux/smpboot.h>
From: David Woodhouse <>

Instead of relying purely on the special-case wrapper in bringup_cpu()
to pass the idle thread to __cpu_up(), expose idle_thread_get() so that
the architecture code can obtain it directly when necessary.

This will be useful when the existing __cpu_up() is split into multiple
phases, only *one* of which will actually need the idle thread.

If the architecture code is to register its new pre-bringup states with
the cpuhp core, having a special-case wrapper to pass extra arguments is
non-trivial and it's easier just to let the arch register its function
pointer to be invoked with the standard API.

Signed-off-by: David Woodhouse <>
Reviewed-by: Thomas Gleixner <>
Signed-off-by: Usama Arif <>
Tested-by: Paul E. McKenney <>
Tested-by: Kim Phillips <>
Tested-by: Oleksandr Natalenko <>
include/linux/smpboot.h | 7 +++++++
kernel/smpboot.h | 2 --
2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/include/linux/smpboot.h b/include/linux/smpboot.h
index 9d1bc65d226c..3862addcaa34 100644
--- a/include/linux/smpboot.h
+++ b/include/linux/smpboot.h
@@ -5,6 +5,13 @@
#include <linux/types.h>

struct task_struct;
+struct task_struct *idle_thread_get(unsigned int cpu);
+static inline struct task_struct *idle_thread_get(unsigned int cpu) { return NULL; }
/* Cookie handed to the thread_fn*/
struct smpboot_thread_data;

diff --git a/kernel/smpboot.h b/kernel/smpboot.h
index 34dd3d7ba40b..60c609318ad6 100644
--- a/kernel/smpboot.h
+++ b/kernel/smpboot.h
@@ -5,11 +5,9 @@
struct task_struct;

-struct task_struct *idle_thread_get(unsigned int cpu);
void idle_thread_set_boot_cpu(void);
void idle_threads_init(void);
-static inline struct task_struct *idle_thread_get(unsigned int cpu) { return NULL; }
static inline void idle_thread_set_boot_cpu(void) { }
static inline void idle_threads_init(void) { }
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