Re: [PATCH v19 31/40] dept: assign unique dept_key to each distinct wait_for_completion() caller

["Gary Guo" <gary@garyguo.net>]

On Mon Jul 6, 2026 at 7:19 AM BST, Byungchul Park wrote:
> wait_for_completion() can be used at various points in the code and it's
> very hard to distinguish wait_for_completion()s between different usages.
> Using a single dept_key for all the wait_for_completion()s could trigger
> false positive reports.
>
> Assign unique dept_key to each distinct wait_for_completion() caller to
> avoid false positive reports.
>
> While at it, add a rust helper for wait_for_completion() to avoid build
> errors.

This will cause Rust code to share the same dept_key, so it will have all the
false positives that the change is trying to avoid.

In general it is easy to create Rust bindings for static inline C functions
because it'll be just some computation, while creating bindings for C
function-like macros that define additional statics can be challenging.

Is dept_key similar to lock_class_key, where only the address matters? If so,
the approach that I use in
https://lore.kernel.org/rust-for-linux/DJP0CDOR98N5.29BK8PUFRWRUK@garyguo.net
could be used for dept_key as well, then we can keep Rust `wait_for_completion`
still a function; otherwise we have to turn it into a macro too on the Rust side
to create such statics, which isn't ideal.

Best,
Gary

>
> Signed-off-by: Byungchul Park <byungchul@sk.com>
> ---
>  include/linux/completion.h | 100 +++++++++++++++++++++++++++++++------
>  kernel/sched/completion.c  |  60 +++++++++++-----------
>  rust/helpers/completion.c  |   5 ++
>  3 files changed, 120 insertions(+), 45 deletions(-)