Re: [PATCH v6] sched: do not call __put_task_struct() on rt if pi_blocked_on is set

["Luis Claudio R. Goncalves" <lgoncalv@redhat.com>]

On Fri, Aug 01, 2025 at 12:24:29PM +0200, Oleg Nesterov wrote:
> On 07/29, Oleg Nesterov wrote:
> >
> > On 07/29, Luis Claudio R. Goncalves wrote:
> > >
> > > On Tue, Jul 29, 2025 at 01:47:03PM +0200, Oleg Nesterov wrote:
> > > > On 07/29, Luis Claudio R. Goncalves wrote:
> > > > >
> > > > > +	/* In !RT, it is always safe to call __put_task_struct(). */
> > > > > +	if (!IS_ENABLED(CONFIG_PREEMPT_RT)) {
> > > > > +		static DEFINE_WAIT_OVERRIDE_MAP(put_task_map, LD_WAIT_SLEEP);
> > > > > +
> > > > > +		lock_map_acquire_try(&put_task_map);
> > > > > +		__put_task_struct(t);
> > > > > +		lock_map_release(&put_task_map);
> > > > > +		return;
> > > > > +	}
> > > >
> > > > FWIW:
> > > >
> > > > Acked-by: Oleg Nesterov <oleg@redhat.com>
> > > >
> > > >
> > > > At the same time... I don't understand this DEFINE_WAIT_OVERRIDE_MAP().
> > > > IIUC, we need to shut up lockdep when put_task_struct() is called under
> > > > raw_spinlock_t and __put_task_struct() paths take spinlock_t, right?
> > > > Perhaps this deserves a comment...
> > >
> > > I reverted that code to the previous state, commit 893cdaaa3977 ("sched:
> > > avoid false lockdep splat in put_task_struct()") and simplified the "if"
> > > statement.
> >
> > Yes, yes, I see and I have already acked your patch.
> 
> So I think you should just resend it.

Thank you! I was a bit unsure on how to proceed :)
 
> s/LD_WAIT_SLEEP/LD_WAIT_CONFIG/ needs another discussion even if I am right,
> sorry for the confusion.

For what is worth, I tested the change with LD_WAIT_CONFIG and it worked as
expected.

Luis

> Oleg.
> 
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