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authorValentin Schneider <valentin.schneider@arm.com>2021-05-10 18:10:23 +0300
committerPeter Zijlstra <peterz@infradead.org>2021-05-18 13:53:53 +0300
commit00b89fe0197f0c55a045775c11553c0cdb7082fe (patch)
tree242f776a1460b80467564ed1156eeacc212dac27 /kernel/kthread.c
parentfcb501704554eebfd27e3220b0540997fd2b24a8 (diff)
downloadlinux-00b89fe0197f0c55a045775c11553c0cdb7082fe.tar.xz
sched: Make the idle task quack like a per-CPU kthread
For all intents and purposes, the idle task is a per-CPU kthread. It isn't created via the same route as other pcpu kthreads however, and as a result it is missing a few bells and whistles: it fails kthread_is_per_cpu() and it doesn't have PF_NO_SETAFFINITY set. Fix the former by giving the idle task a kthread struct along with the KTHREAD_IS_PER_CPU flag. This requires some extra iffery as init_idle() call be called more than once on the same idle task. Signed-off-by: Valentin Schneider <valentin.schneider@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20210510151024.2448573-2-valentin.schneider@arm.com
Diffstat (limited to 'kernel/kthread.c')
-rw-r--r--kernel/kthread.c30
1 files changed, 18 insertions, 12 deletions
diff --git a/kernel/kthread.c b/kernel/kthread.c
index fe3f2a40d61e..3d326833092b 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -68,16 +68,6 @@ enum KTHREAD_BITS {
KTHREAD_SHOULD_PARK,
};
-static inline void set_kthread_struct(void *kthread)
-{
- /*
- * We abuse ->set_child_tid to avoid the new member and because it
- * can't be wrongly copied by copy_process(). We also rely on fact
- * that the caller can't exec, so PF_KTHREAD can't be cleared.
- */
- current->set_child_tid = (__force void __user *)kthread;
-}
-
static inline struct kthread *to_kthread(struct task_struct *k)
{
WARN_ON(!(k->flags & PF_KTHREAD));
@@ -103,6 +93,22 @@ static inline struct kthread *__to_kthread(struct task_struct *p)
return kthread;
}
+void set_kthread_struct(struct task_struct *p)
+{
+ struct kthread *kthread;
+
+ if (__to_kthread(p))
+ return;
+
+ kthread = kzalloc(sizeof(*kthread), GFP_KERNEL);
+ /*
+ * We abuse ->set_child_tid to avoid the new member and because it
+ * can't be wrongly copied by copy_process(). We also rely on fact
+ * that the caller can't exec, so PF_KTHREAD can't be cleared.
+ */
+ p->set_child_tid = (__force void __user *)kthread;
+}
+
void free_kthread_struct(struct task_struct *k)
{
struct kthread *kthread;
@@ -272,8 +278,8 @@ static int kthread(void *_create)
struct kthread *self;
int ret;
- self = kzalloc(sizeof(*self), GFP_KERNEL);
- set_kthread_struct(self);
+ set_kthread_struct(current);
+ self = to_kthread(current);
/* If user was SIGKILLed, I release the structure. */
done = xchg(&create->done, NULL);