Re: [PATCH] rust: task: mark Task methods inline

[Panagiotis Foliadis]

On 10/3/25 12:23, Alice Ryhl wrote:
> On Mon, Mar 10, 2025 at 10:40 AM Panagiotis Foliadis
> <pfoliadis@xxxxxxxxxx> wrote:
> > When you build the kernel using the llvm-18.1.3-rust-1.85.0-x86_64
> > toolchain provided by kernel.org, the following symbols are generated:
> >
> > $ nm vmlinux | grep ' _R'.*Task | rustfilt
> > ffffffff817b2d30 T <kernel::task::Task>::get_pid_ns
> > ffffffff817b2d50 T <kernel::task::Task>::tgid_nr_ns
> > ffffffff817b2c90 T <kernel::task::Task>::current_pid_ns
> > ffffffff817b2d00 T <kernel::task::Task>::signal_pending
> > ffffffff817b2cc0 T <kernel::task::Task>::uid
> > ffffffff817b2ce0 T <kernel::task::Task>::euid
> > ffffffff817b2c70 T <kernel::task::Task>::current
> > ffffffff817b2d70 T <kernel::task::Task>::wake_up
> > ffffffff817b2db0 T <kernel::task::Task as kernel::types::AlwaysRefCounted>::dec_ref
> > ffffffff817b2d90 T <kernel::task::Task as kernel::types::AlwaysRefCounted>::inc_ref
> >
> > Most of these Rust symbols are trivial wrappers around the C functions
> > signal_pending, uid, euid, wake_up, dec_ref and inc_ref.It doesn't
> > make sense to go through a trivial wrapper for these functions, so
> > mark them inline.
> There's no C function called dec_ref or inc_ref? Please use the C
> function names instead of the Rust ones.
>
> > After applying this patch, the above command will produce this output:
> >
> > ffff8000805aa004 T <kernel::task::Task>::get_pid_ns
> > ffff8000805aa01c T <kernel::task::Task>::tgid_nr_ns
> > ffff8000805a9fe8 T <kernel::task::Task>::current_pid_ns
> > ffff8000805a9fd0 T <kernel::task::Task>::current
> I think it'd be nice with an explanation of why you did not mark these
> #[inline].

Since the issue focuses on the functions that are trivial wrappers around
c and `do nothing that call a C function` I thought i would leave this out
since there is some other functionality (albeit sometimes minimal) other
that being just a c-wrapper.

> > Signed-off-by: Panagiotis Foliadis <pfoliadis@xxxxxxxxxx>
> > Link: https://github.com/Rust-for-Linux/linux/issues/1145
> The SoB usually goes at the bottom of the tags.
>
> >   rust/kernel/task.rs | 6 ++++++
> >   1 file changed, 6 insertions(+)
> >
> > diff --git a/rust/kernel/task.rs b/rust/kernel/task.rs
> > index 07bc22a7645c0c7d792a0a163dd55b8ff0fe5f92..996d7c96e48689a5752817f9ca196c021865291d 100644
> > --- a/rust/kernel/task.rs
> > +++ b/rust/kernel/task.rs
> > @@ -273,18 +273,21 @@ pub fn pid(&self) -> Pid {
> >       }
> >
> >       /// Returns the UID of the given task.
> > +    #[inline]
> >       pub fn uid(&self) -> Kuid {
> >           // SAFETY: It's always safe to call `task_uid` on a valid task.
> >           Kuid::from_raw(unsafe { bindings::task_uid(self.as_ptr()) })
> >       }
> >
> >       /// Returns the effective UID of the given task.
> > +    #[inline]
> >       pub fn euid(&self) -> Kuid {
> >           // SAFETY: It's always safe to call `task_euid` on a valid task.
> >           Kuid::from_raw(unsafe { bindings::task_euid(self.as_ptr()) })
> >       }
> >
> >       /// Determines whether the given task has pending signals.
> > +    #[inline]
> >       pub fn signal_pending(&self) -> bool {
> >           // SAFETY: It's always safe to call `signal_pending` on a valid task.
> >           unsafe { bindings::signal_pending(self.as_ptr()) != 0 }
> > @@ -319,6 +322,7 @@ pub fn tgid_nr_ns(&self, pidns: Option<&PidNamespace>) -> Pid {
> >       }
> >
> >       /// Wakes up the task.
> > +    #[inline]
> >       pub fn wake_up(&self) {
> >           // SAFETY: It's always safe to call `signal_pending` on a valid task, even if the task
> >           // running.
> > @@ -328,11 +332,13 @@ pub fn wake_up(&self) {
> >
> >   // SAFETY: The type invariants guarantee that `Task` is always refcounted.
> >   unsafe impl crate::types::AlwaysRefCounted for Task {
> > +    #[inline]
> >       fn inc_ref(&self) {
> >           // SAFETY: The existence of a shared reference means that the refcount is nonzero.
> >           unsafe { bindings::get_task_struct(self.as_ptr()) };
> >       }
> >
> > +    #[inline]
> >       unsafe fn dec_ref(obj: ptr::NonNull<Self>) {
> >           // SAFETY: The safety requirements guarantee that the refcount is nonzero.
> >           unsafe { bindings::put_task_struct(obj.cast().as_ptr()) }
> >
> > ---
> > base-commit: 7f0e9ee5e44887272627d0fcde0b19a675daf597
> > change-id: 20250308-inline-c-wrappers-da83ec1c2a77
> >
> > Best regards,
> > --
> > Panagiotis Foliadis <pfoliadis@xxxxxxxxxx>