Re: [PATCH v8 1/4] rust: helpers: add SRCU helpers

[Gary Guo]

On Fri May 29, 2026 at 12:43 PM BST, Onur Özkan wrote:
> Add helper wrappers for SRCU functions that are exposed to Rust
> through generated bindings.
>
> Reviewed-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
> Signed-off-by: Onur Özkan <work@xxxxxxxxxxxxx>
> ---
>  include/linux/srcu.h   |  5 +++++
>  rust/helpers/helpers.c |  1 +
>  rust/helpers/srcu.c    | 30 ++++++++++++++++++++++++++++++
>  3 files changed, 36 insertions(+)
>  create mode 100644 rust/helpers/srcu.c
>
> diff --git a/include/linux/srcu.h b/include/linux/srcu.h
> index 81b1938512d5..790a4ef713c0 100644
> --- a/include/linux/srcu.h
> +++ b/include/linux/srcu.h
> @@ -57,6 +57,11 @@ int __init_srcu_struct_fast_updown(struct srcu_struct *ssp, const char *name,
>  #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
>  
>  int init_srcu_struct(struct srcu_struct *ssp);
> +static inline int __init_srcu_struct(struct srcu_struct *ssp, const char *name,
> +				     struct lock_class_key *key)
> +{
> +	return init_srcu_struct(ssp);
> +}


This looks like a different strategy than, say, how mutex handles lockdep. IMO
the way that mutex handles this is more clear.

If we follow the way mutex is handles this, the `init_srcu_struct` would always
create lock class key and forward to `__init_srcu_struct`, and
`__init_srcu_struct` is an inline function that either calls
`init_srcu_struct_lockdep` with all args, or discard name/key and forward to
`init_srcu_struct_mutex`.

This is beneficial because the usage flows one way. You don't have in one config
`init_srcu_struct` call `__init_srcu_struct` and have the opposite in another
config, which I think can be quite confusing.

Best,
Gary

>  #ifndef CONFIG_TINY_SRCU
>  int init_srcu_struct_fast(struct srcu_struct *ssp);
>  int init_srcu_struct_fast_updown(struct srcu_struct *ssp);
> diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c
> index 625921e27dfb..f3562d3b3888 100644
> --- a/rust/helpers/helpers.c
> +++ b/rust/helpers/helpers.c
> @@ -88,6 +88,7 @@
>  #include "signal.c"
>  #include "slab.c"
>  #include "spinlock.c"
> +#include "srcu.c"
>  #include "sync.c"
>  #include "task.c"
>  #include "time.c"
> diff --git a/rust/helpers/srcu.c b/rust/helpers/srcu.c
> new file mode 100644
> index 000000000000..225b3bf9334a
> --- /dev/null
> +++ b/rust/helpers/srcu.c
> @@ -0,0 +1,30 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <linux/srcu.h>
> +
> +__rust_helper int rust_helper_init_srcu_struct_with_key(struct srcu_struct *ssp,
> +							const char *name,
> +							struct lock_class_key *key)
> +{
> +	return __init_srcu_struct(ssp, name, key);
> +}
> +
> +__rust_helper int rust_helper_srcu_read_lock(struct srcu_struct *ssp)
> +{
> +	return srcu_read_lock(ssp);
> +}
> +
> +__rust_helper void rust_helper_srcu_read_unlock(struct srcu_struct *ssp, int idx)
> +{
> +	srcu_read_unlock(ssp, idx);
> +}
> +
> +__rust_helper void rust_helper_srcu_barrier(struct srcu_struct *ssp)
> +{
> +	srcu_barrier(ssp);
> +}
> +
> +__rust_helper void rust_helper_synchronize_srcu_expedited(struct srcu_struct *ssp)
> +{
> +	synchronize_srcu_expedited(ssp);
> +}