On Wed, May 20, 2020 at 08:18:58PM +0200, Greg Kroah-Hartman wrote:
> On Wed, May 20, 2020 at 05:25:09PM +0530, Pavankumar Kondeti wrote:
> > When kernel threads are created for later use, they will be in
> > TASK_UNINTERRUPTIBLE state until they are woken up. This results
> > in increased loadavg and false hung task reports. To fix this,
> > use TASK_IDLE state instead of TASK_UNINTERRUPTIBLE when
> > a kernel thread schedules out for the first time.
> >
> > Signed-off-by: Pavankumar Kondeti <pkond...@codeaurora.org>
> > ---
> > kernel/kthread.c | 6 +++---
> > 1 file changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/kernel/kthread.c b/kernel/kthread.c
> > index bfbfa48..b74ed8e 100644
> > --- a/kernel/kthread.c
> > +++ b/kernel/kthread.c
> > @@ -250,7 +250,7 @@ static int kthread(void *_create)
> > current->vfork_done = &self->exited;
> >
> > /* OK, tell user we're spawned, wait for stop or wakeup */
> > - __set_current_state(TASK_UNINTERRUPTIBLE);
> > + __set_current_state(TASK_IDLE);
> > create->result = current;
> > /*
> > * Thread is going to call schedule(), do not preempt it,
> > @@ -428,7 +428,7 @@ static void __kthread_bind(struct task_struct *p,
> > unsigned int cpu, long state)
> >
> > void kthread_bind_mask(struct task_struct *p, const struct cpumask *mask)
> > {
> > - __kthread_bind_mask(p, mask, TASK_UNINTERRUPTIBLE);
> > + __kthread_bind_mask(p, mask, TASK_IDLE);
> > }
> >
> > /**
> > @@ -442,7 +442,7 @@ void kthread_bind_mask(struct task_struct *p, const
> > struct cpumask *mask)
> > */
> > void kthread_bind(struct task_struct *p, unsigned int cpu)
> > {
> > - __kthread_bind(p, cpu, TASK_UNINTERRUPTIBLE);
> > + __kthread_bind(p, cpu, TASK_IDLE);
> > }
> > EXPORT_SYMBOL(kthread_bind);
>
> It's as if people never read mailing lists:
>
> https://lore.kernel.org/r/dm6pr11mb3531d3b164357b2dc476102ddf...@dm6pr11mb3531.namprd11.prod.outlook.com
>
> Given that this is an identical resend of the previous patch, why are
> you doing so, and what has changed since that original rejection?
>
I did not know that it is attempted before. Thanks for pointing to the
previous discussion.
We have seen hung task reports from customers and it is due to a downstream
change which create bunch of kernel threads for later use. From Peter's
reply, I understood that one must wake up the kthread after creation and put
it in INTERRUPTIBLE sleep. I will pass on the message.
Thanks,
Pavan
--
Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux
Foundation Collaborative Project.
