Re: [PATCH v7 0/4] rust: helpers: add SRCU helpers

[Paul E. McKenney]

On Thu, May 28, 2026 at 09:27:32AM +0300, Onur Özkan wrote:
> The immediate motivation is the Tyr reset infrastructure [1] which needs
> to serialize reset sensitive hardware access against reset and teardown
> paths. That reset series started to require many independent dependencies
> so this SRCU support is split out as a standalone Rust API to keep the
> reset series focused on the reset logic and easier to review, rebase and
> land.

For the first two:

Reviewed-by: Paul E. McKenney <paulmck@xxxxxxxxxx>

They also pass short rcutorture testing, which is reassuring:

tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --duration 40 --configs "SRCU-N SRCU-P SRCU-T SRCU-U" --trust-make

> Changes since v6:
> 
> - Removed "CONFIG_DEBUG_LOCK_ALLOC" condition from "rust/helpers/srcu.c"
>   and created a simple wrapper inside "include/linux/srcu.h" for it.
> 
> v6: https://lore.kernel.org/all/20260527203615.163688-1-work@xxxxxxxxxxxxx
> 
> Changes since v5:
> 
> - Created separate srcu_readers_active() variants for "srcutiny.h" and
>   "srcutree.h".
> 
> v5: https://lore.kernel.org/all/20260527174120.510447-1-work@xxxxxxxxxxxxx
> 
> Changes since v4:
> 
> - Exposed srcu_readers_active from C side and wired it to the Rust
>   helpers.
> - Used srcu_readers_active() in SRCU drop and logged with pr_warn if
>   there are leaked guards during the drop.
> 
> v4: https://lore.kernel.org/all/20260525175706.124910-1-work@xxxxxxxxxxxxx
> 
> Changes since v3 (which are for Sashiko notes [2]):
> 
> - Added rust helpers for srcu_barrier() and synchronize_srcu_expedited()
>   so the abstraction builds with CONFIG_TINY_SRCU, where these are
>   static inline functions.
> - Added missing INVARIANT comment in Srcu::new() about why the type
>   invariants hold after successful initialization.
> 
> v3: https://lore.kernel.org/all/20260522054228.114814-1-work@xxxxxxxxxxxxx
> 
> Changes since v2:
> 
> - Removed closure-based API.
> - Added #[doc(hidden)] on new_srcu macro.
> - Added #[must_use..] on srcu::Guard.
> - Improved the clean-up path (PinnedDrop implementation) which
>   eventually made read_lock safe with leaked guards.
> 
> v2: https://lore.kernel.org/all/20260502162833.34334-1-work@xxxxxxxxxxxxx
> 
> Changes since v1:
> 
> - Made the owned SRCU read-side guard API unsafe and added a safe closure
>   based helper for callers that do not need to keep the guard. This is to
>   avoid UB on the C side cleanup_srcu_struct where the SRCU struct is freed
>   while there are still active guards, which can happen if the caller leaks
>   the guard e.g., with mem::forget().
> - Improved doc comments.
> 
> v1: https://lore.kernel.org/all/20260428103437.156236-1-work@xxxxxxxxxxxxx
> 
> 
> [1]: https://lore.kernel.org/all/20260416171728.205141-1-work@xxxxxxxxxxxxx
> [2]: https://sashiko.dev/#/patchset/20260522054228.114814-1-work@xxxxxxxxxxxxx?part=2
> 
> Onur Özkan (4):
>   rust: helpers: add SRCU helpers
>   srcu: expose srcu_readers_active()
>   rust: sync: add SRCU abstraction
>   MAINTAINERS: add Rust SRCU files to SRCU entry
> 
>  MAINTAINERS              |   3 +
>  include/linux/srcu.h     |   5 ++
>  include/linux/srcutiny.h |  13 +++
>  include/linux/srcutree.h |  24 ++++++
>  kernel/rcu/srcutiny.c    |   2 +-
>  kernel/rcu/srcutree.c    |  25 ------
>  rust/helpers/helpers.c   |   1 +
>  rust/helpers/srcu.c      |  35 +++++++++
>  rust/kernel/sync.rs      |   2 +
>  rust/kernel/sync/srcu.rs | 166 +++++++++++++++++++++++++++++++++++++++
>  10 files changed, 250 insertions(+), 26 deletions(-)
>  create mode 100644 rust/helpers/srcu.c
>  create mode 100644 rust/kernel/sync/srcu.rs
> 
> -- 
> 2.51.2
> 
>