On Tue, Jul 22, 2025 at 06:11:00PM -0400, Joel Fernandes wrote:
> On Mon, Jul 21, 2025 at 09:24:31AM -0700, Paul E. McKenney wrote:
> > This commit adds no-trace variants of the srcu_read_lock_fast() and
> > srcu_read_unlock_fast() functions for tracing use.
> >
> > Signed-off-by: Paul E. McKenney <paul...@kernel.org>
> > Cc: Mathieu Desnoyers <mathieu.desnoy...@efficios.com>
> > Cc: Steven Rostedt <rost...@goodmis.org>
> > Cc: Sebastian Andrzej Siewior <bige...@linutronix.de>
> > ---
> > include/linux/srcu.h | 25 +++++++++++++++++++++++++
> > 1 file changed, 25 insertions(+)
> >
> > diff --git a/include/linux/srcu.h b/include/linux/srcu.h
> > index 478c73d067f7d..7a692bf8f99b9 100644
> > --- a/include/linux/srcu.h
> > +++ b/include/linux/srcu.h
> > @@ -282,6 +282,20 @@ static inline struct srcu_ctr __percpu
> > *srcu_read_lock_fast(struct srcu_struct *
> > return retval;
> > }
> >
> > +/*
> > + * Used by tracing, cannot be traced and cannot call lockdep.
> > + * See srcu_read_lock_fast() for more information.
> > + */
> > +static inline struct srcu_ctr __percpu *srcu_read_lock_fast_notrace(struct
> > srcu_struct *ssp)
> > + __acquires(ssp)
>
> Should these also be marked with 'notrace' attribute?
>
> I am not sure what the precedent is, I do see a few examples of 'notrace' and
> 'inline' in the same function signature though.
Heh!!!
There are six instance of static-inline notrace functions, and eight
instances of static-inline non-notrace functions whose names contain
"_notrace", not counting the srcu_read_lock_fast_notrace() and
srcu_read_unlock_fast() functions currently under review.
My guess is that I should add "notrace" to handle the possible case
where the compiler declines to inline this function. I will do this
on the next rebase unless I hear otherwise.
Steven, Mathieu, thoughts?
Thanx, Paul
> Other than that one nit:
> Reviewed-by: Joel Fernandes <joelagn...@nvidia.com>
>
> thanks,
>
> - Joel
>
>
> > +{
> > + struct srcu_ctr __percpu *retval;
> > +
> > + srcu_check_read_flavor_force(ssp, SRCU_READ_FLAVOR_FAST);
> > + retval = __srcu_read_lock_fast(ssp);
> > + return retval;
> > +}
> > +
> > /**
> > * srcu_down_read_fast - register a new reader for an SRCU-protected
> > structure.
> > * @ssp: srcu_struct in which to register the new reader.
> > @@ -394,6 +408,17 @@ static inline void srcu_read_unlock_fast(struct
> > srcu_struct *ssp, struct srcu_ct
> > RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching
> > srcu_read_unlock_fast().");
> > }
> >
> > +/*
> > + * Used by tracing, cannot be traced and cannot call lockdep.
> > + * See srcu_read_unlock_fast() for more information.
> > + */
> > +static inline void srcu_read_unlock_fast_notrace(struct srcu_struct *ssp,
> > + struct srcu_ctr __percpu *scp)
> > __releases(ssp)
> > +{
> > + srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_FAST);
> > + __srcu_read_unlock_fast(ssp, scp);
> > +}
> > +
> > /**
> > * srcu_up_read_fast - unregister a old reader from an SRCU-protected
> > structure.
> > * @ssp: srcu_struct in which to unregister the old reader.
> > --
> > 2.40.1
> >
