Re: [PATCH] srcutree: Add lockdep and early-boot checks to synchronize_srcu_atomic()

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

> 
> On Sat, Sep 12, 2026 at 08:37:33PM +0800, KunWu Chan wrote:
> 
> > 
> > On Sat, Sep 12, 2026 at 12:47 AM Paul E. McKenney <paulmck@kernel.org> wrote:
> > 
> >  On Fri, Sep 11, 2026 at 05:35:15PM +0800, Kunwu Chan wrote:
> >  > Add the lockdep annotation, same-type SRCU nesting warning, and
> >  > early-boot check used by __synchronize_srcu().
> >  >
> >  > Suggested-by: Zqiang <qiang.zhang@linux.dev>
> >  > Signed-off-by: Kunwu Chan <kunwu.chan@gmail.com>
> > 
> >  Queued for review and testing, thank you both!
> > 
> >  Interestingly enough, it is now the case that there is a grace-period
> >  wait that can be placed in a normal RCU read-side critical section.
> >  Does this mean that we should also adjust the --do-srcu-lockdep testing
> >  in tools/testing/selftests/rcutorture/bin/torture.sh?
> >  
> >  Thanks, Paul. Good point.
> >  
> >  I’ll check the current `--do-srcu-lockdep` coverage, including the
> >  case where `synchronize_srcu_atomic()` is called from a normal RCU
> >  read-side critical section, and follow up with the necessary torture
> >  testing changes.
> > 
> Sounds good!
> 
> Perhaps you and Zqiang can work together on this. Co-developed-by,
> for example.

Hi, Paul and KunWu

Should we also consider the following situations ?


idx = srcu_read_lock_atomic(srcu)

by interrupt run hardirq context:
   synchronize_rcu_atomic(srcu)

srcu_read_unlock_atomic(srcu, idx)


or:



           CPU0:                                                                  CPU1:                                           

idx = srcu_read_lock_atomic(srcu)

smp_call_function_single(CPU1, som_func, NULL, 1)
to send IPI to CPU1, and sync wait complete.
                                                                   hardirq context or ide task context:

                                                                          some_func()
                                                                          ->synchronize_rcu_atomic(srcu)  

srcu_read_unlock_atomic(srcu, idx)


Add WARN_ON(irqs_disabled()) to synchronize_rcu_atomic() ?

Any thoughts?

Thanks
Zqiang


> 
>  Thanx, Paul
> 
> > 
> > Thanks,
> >  Kunwu
> >  
> > 
> >  Thanx, Paul
> > 
> >  > ---
> >  > kernel/rcu/srcutree.c | 8 ++++++++
> >  > 1 file changed, 8 insertions(+)
> >  >
> >  > diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
> >  > index 6a9c432a3bd0..6c729e805fb3 100644
> >  > --- a/kernel/rcu/srcutree.c
> >  > +++ b/kernel/rcu/srcutree.c
> >  > @@ -2123,6 +2123,14 @@ void synchronize_srcu_atomic(struct srcu_struct *ssp)
> >  > unsigned long rdm0, rdm1;
> >  > unsigned long unlocks0, unlocks1;
> >  >
> >  > + srcu_lock_sync(&ssp->dep_map);
> >  > +
> >  > + RCU_LOCKDEP_WARN(lockdep_is_held(ssp),
> >  > + "Illegal synchronize_srcu_atomic() in same-type SRCU read-side critical section");
> >  > +
> >  > + if (rcu_scheduler_active == RCU_SCHEDULER_INACTIVE)
> >  > + return;
> >  > +
> >  > // Initialize. Either init_srcu_struct() was invoked or
> >  > // DEFINE_SRCU() or similar was used. Therefore, no allocation
> >  > // will be done here.
> >  > --
> >  > 2.43.0
> >  >
> >
>