Re: [PATCH v3] rust: sync: export lock::do_unlocked

[Boqun Feng]

On Tue, Sep 29, 2026 at 08:03:20PM +0200, Andreas Hindborg wrote:
> "Gary Guo" <gary@xxxxxxxxxxx> writes:
> 
> > On Tue Sep 29, 2026 at 3:45 PM BST, Andreas Hindborg wrote:
> >> Export lock::do_unlocked publicly. Add documentation for the method.
> >>
> >> Reviewed-by: Benno Lossin <lossin@xxxxxxxxxx>
> >> Reviewed-by: Alice Ryhl <aliceryhl@xxxxxxxxxx>
> >> Signed-off-by: Andreas Hindborg <a.hindborg@xxxxxxxxxx>
> >> ---
> >> Changes in v3:
> >> - Rebase on v7.3-rc5.
> >> - Do not import prelude in example (Alice).
> >> - Link to v2: https://msgid.link/20260605-export-do-unlocked-v2-1-e23001390231@xxxxxxxxxx
> >>
> >> Changes in v2:
> >> - Drop spurious space before `guard.do_unlocked` in the doc example (Benno).
> >> - Un-hide the imports in the doc example so the rendered docs no longer have a spurious blank line after them (Alice).
> >> - Link to v1: https://msgid.link/20260215-export-do-unlocked-v1-1-f5cd2203b20f@xxxxxxxxxx
> >> ---
> >>  rust/kernel/sync/lock.rs | 26 +++++++++++++++++++++++++-
> >>  1 file changed, 25 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/rust/kernel/sync/lock.rs b/rust/kernel/sync/lock.rs
> >> index 10b6b5e9b024..edfff9e10199 100644
> >> --- a/rust/kernel/sync/lock.rs
> >> +++ b/rust/kernel/sync/lock.rs
> >> @@ -238,7 +238,31 @@ pub fn lock_ref(&self) -> &'a Lock<T, B> {
> >>          self.lock
> >>      }
> >>
> >> -    pub(crate) fn do_unlocked<U>(&mut self, cb: impl FnOnce() -> U) -> U {
> >> +    /// Temporarily unlock the lock to execute the given closure.
> >> +    ///
> >> +    /// This method unlocks the lock before calling the closure `cb`, and re-locks it afterwards.
> >> +    /// This is useful when you need to perform operations that are not allowed while holding
> >> +    /// certain locks, such as allocating memory (which is prohibited while holding a spinlock).
> >> +    ///
> >> +    /// # Examples
> >> +    ///
> >> +    /// ```
> >> +    /// use kernel::new_spinlock;
> >> +    /// use pin_init::stack_pin_init;
> >> +    ///
> >> +    /// stack_pin_init!{
> >> +    ///     let lock = new_spinlock!(())
> >> +    /// }
> >> +    ///
> >> +    /// let mut guard = lock.lock();
> >> +    /// let mut buffer = KVec::new();
> >> +    /// // Temporarily unlock to allocate memory, which should not be done while holding a spinlock.
> >> +    /// guard.do_unlocked(|| {
> >> +    ///     buffer.push(5u32, GFP_KERNEL)
> >> +    /// })?;
> >> +    /// # Ok::<(), Error>(())
> >> +    /// ```
> >> +    pub fn do_unlocked<U>(&mut self, cb: impl FnOnce() -> U) -> U {
> >
> > Do we want to keep the name `do_unlocked` now this is public?
> >
> > I think we can drop "do_" and just call this `unlocked`, consistent with popular
> > Rust ecosystem crates like parking_lot and spin.
> 

I didn't find a unlocked() in spin. You mean
https://crates.io/crates/lock_api ?

To me, `do_unlocked()` is better, since it indicates something is going
to be done after the lock being dropped.

Regards,
Boqun

> If this is the established way, I think we should do that.
> 
> I don't think we need a new version of the patch, just fix it during
> apply?
> 
> Best regards,
> Andreas Hindborg
> 
> 
>