On Wed, Jul 23, 2025 at 01:27:56PM -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.
>
> [ paulmck: Apply notrace feedback from Joel Fernandes, Steven Rostedt, and
> Mathieu Desnoyers. ]
>
> Link: https://lore.kernel.org/all/[email protected]
> Signed-off-by: Paul E. McKenney <[email protected]>
> Reviewed-by: Joel Fernandes <[email protected]>
> Cc: Mathieu Desnoyers <[email protected]>
> Cc: Steven Rostedt <[email protected]>
> Cc: Sebastian Andrzej Siewior <[email protected]>
> Cc: <[email protected]>
> ---
> include/linux/srcu.h | 30 ++++++++++++++++++++++++++++--
> include/linux/srcutree.h | 5 +++--
> 2 files changed, 31 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/srcu.h b/include/linux/srcu.h
> index 478c73d067f7d..ec3b8e27d6c5a 100644
> --- a/include/linux/srcu.h
> +++ b/include/linux/srcu.h
> @@ -271,7 +271,7 @@ static inline int srcu_read_lock(struct srcu_struct *ssp)
> __acquires(ssp)
> * where RCU is watching, that is, from contexts where it would be legal
> * to invoke rcu_read_lock(). Otherwise, lockdep will complain.
> */
> -static inline struct srcu_ctr __percpu *srcu_read_lock_fast(struct
> srcu_struct *ssp) __acquires(ssp)
> +static inline struct srcu_ctr __percpu notrace *srcu_read_lock_fast(struct
> srcu_struct *ssp) __acquires(ssp)
Hmm.. am I missing something, why do we need ot make
srcu_read_lock_fast() notrace? I thought we only need those _notrace()
variants notrace?
Regards,
Boqun
> {
> struct srcu_ctr __percpu *retval;
>
> @@ -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)
> +{
> + 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.
> @@ -385,7 +399,8 @@ static inline void srcu_read_unlock(struct srcu_struct
> *ssp, int idx)
> *
> * Exit a light-weight SRCU read-side critical section.
> */
> -static inline void srcu_read_unlock_fast(struct srcu_struct *ssp, struct
> srcu_ctr __percpu *scp)
> +static inline void notrace
> +srcu_read_unlock_fast(struct srcu_struct *ssp, struct srcu_ctr __percpu *scp)
> __releases(ssp)
> {
> srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_FAST);
> @@ -394,6 +409,17 @@ 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.
> diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h
> index 043b5a67ef71e..4d2fee4d38289 100644
> --- a/include/linux/srcutree.h
> +++ b/include/linux/srcutree.h
> @@ -240,7 +240,7 @@ static inline struct srcu_ctr __percpu
> *__srcu_ctr_to_ptr(struct srcu_struct *ss
> * on architectures that support NMIs but do not supply NMI-safe
> * implementations of this_cpu_inc().
> */
> -static inline struct srcu_ctr __percpu *__srcu_read_lock_fast(struct
> srcu_struct *ssp)
> +static inline struct srcu_ctr __percpu notrace *__srcu_read_lock_fast(struct
> srcu_struct *ssp)
> {
> struct srcu_ctr __percpu *scp = READ_ONCE(ssp->srcu_ctrp);
>
> @@ -267,7 +267,8 @@ static inline struct srcu_ctr __percpu
> *__srcu_read_lock_fast(struct srcu_struct
> * on architectures that support NMIs but do not supply NMI-safe
> * implementations of this_cpu_inc().
> */
> -static inline void __srcu_read_unlock_fast(struct srcu_struct *ssp, struct
> srcu_ctr __percpu *scp)
> +static inline void notrace
> +__srcu_read_unlock_fast(struct srcu_struct *ssp, struct srcu_ctr __percpu
> *scp)
> {
> barrier(); /* Avoid leaking the critical section. */
> if (!IS_ENABLED(CONFIG_NEED_SRCU_NMI_SAFE))
> --
> 2.40.1
>
>
