On Thu, May 21, 2020 at 07:05:44AM +0530, Pavan Kondeti wrote:
> 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.
Do you have a pointer to that specific change?
> 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.
Just go fix that code, it sounds like it's in your tree already :)
thanks,
greg k-h
