Re: [BUG] srcu: false-positive WARN in cleanup_srcu_struct() after 78a38cbf6f20

["Zqiang" <qiang.zhang@linux.dev>]

> 
> On 8/27/26 21:40, Zqiang wrote:
> 
> > 
> > Now, I am trying to rephrase your problem in the following way:
> >  1- the step1 call_srcu() trigger SRCU grace period has been end and queue sdp->work.
> >  2- the step4 queue srcu callback has been intercepted by step5 srcu_barrier()
> >  and start a new SRCU grace period.
> >  3- this new SRCU grace period end, and invoke rcu_seq_end(&sup->srcu_gp_seq), queue a timer.
> >  4- the sdp->work begin run, and call srcu_segcblist_advance() with current sup->srcu_gp_seq.
> >  so the step4's srcu callback and step5's barrier calback both to be run.
> >  all callback finished, but the len not yet update.
> >  5- the srcu_barrier() return, begin call srcu_clean_up(), and then the srcu_clean_up
> >  find the a timer is still pending and the cb_len also not be zero, trigger WARN_ON()
> >  right?
> > 
> Exactly. The real callbacks are properly invoked as srcu_barrier() guarantees. The WARN is triggered only by the two transient states: a pending delay_work timer and a stale cblist len. So I think this is a false positive warning.
> 
> Sorry if my explanations were too wordy.

Would you like to send a patch to fix it ?

remove WARN_ON() or use rcu_segcblist_empty(&sdp->srcu_cblist) to replace rcu_segcblist_n_cbs(&sdp->srcu_cblist) ?

Let's hear Paul's opinion.

Thanks
Zqiang

> 
> Thanks
> Sunho Park
>