Re: Possible enhancement to RCU CPU stall warning messages

[Steven Rostedt <rostedt@goodmis.org>]

On Fri, 16 Oct 2026 09:00:31 -0700
"Paul E. McKenney" <paulmck@kernel.org> wrote:

> > > @@ -372,17 +381,24 @@ static int rcu_print_task_stall(struct rcu_node *rnp, unsigned long flags)
> > >  	raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
> > >  	while (i) {
> > >  		t = ts[--i];
> > > -		if (task_call_func(t, check_slow_task, &rscr))
> > > +		if (task_call_func(t, check_slow_task, &rscr)) {
> > >  			pr_cont(" P%d", t->pid);
> > > -		else
> > > -			pr_cont(" P%d/%d:%c%c%c%c%c%c",
> > > +		} else {
> > > +			tc = rscr.rcu_rdr_cpu_task;  
> > 
> > Is there a possible race between the call to rcu_cpu_curr() and here, where
> > that task could have exited and is freed?
> > 
> > There's no get_task_struct() on that task.  
> 
> The get_task_struct() happens in the list_for_each_entry_continue()
> loop that it right before the raw_spin_unlock_irqrestore_rcu_node().
> 
> Or do I have an off-by-one bug here?
> 

But doesn't that loop just cover the tasks in &rnp->blkd_tasks?

Does that include the task returned by cpu_curr(cpu) ?

-- Steve