Re: [PATCH v2 03/14] rust: sync: add `Arc::as_ptr`
From: Dirk Behme
Date: Tue Oct 01 2024 - 00:57:10 EST
On 19.09.2024 16:03, Benno Lossin wrote:
On 18.09.24 00:27, Andreas Hindborg wrote:
Add a method to get a pointer to the data contained in an `Arc`.
Signed-off-by: Andreas Hindborg <a.hindborg@xxxxxxxxxx>
---
rust/kernel/sync/arc.rs | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs
index 3673496c2363..a57ea3e2b44c 100644
--- a/rust/kernel/sync/arc.rs
+++ b/rust/kernel/sync/arc.rs
@@ -258,6 +258,14 @@ pub fn into_raw(self) -> *const T {
unsafe { core::ptr::addr_of!((*ptr).data) }
}
+ /// Return a raw pointer to the data in this arc.
+ pub fn as_ptr(&self) -> *const T {
I don't know if we have a convention for this, but shouldn't this be an
associated function? Because if `T` also has an `as_ptr` function, it
will be shadowed by this one.
Yes. In Fabien's out of tree regmap we have an as_ptr() for Regmap [1]
which operates on &Arc<Regmap> [2]. Once this patch is applied to arc.rs
the compilation fails as then Arc.as_ptr() is used, not the
Regmap.as_ptr() any more [3]. Switching this to something like [4] makes
the compiler happy.
Thanks,
Dirk
P.S.: Just to learn something: For the unmodified, failing case: Is
there a rule when which as_ptr() will be used? Is there an order rule
for the shadowing? Any documentation link?
[1]
https://github.com/Fabo/linux/blob/fparent/rust-ncv6336/rust/kernel/regmap.rs#L71
[2]
https://github.com/Fabo/linux/blob/fparent/rust-ncv6336/rust/kernel/regulator/driver.rs#L418
[3]
error[E0308]: mismatched types
--> rust/kernel/regulator/driver.rs:420:33
|
420 | config.cfg.regmap = regmap.as_ptr();
| ^^^^^^^^^^^^^^^ types differ in
mutability
|
= note: expected raw pointer `*mut bindings::regmap`
found raw pointer `*const Regmap`
error: aborting due to 1 previous error
[4]
diff --git a/rust/kernel/hrtimer/arc.rs b/rust/kernel/hrtimer/arc.rs
index ff04b0b75bb39..7c39ab440e1c6 100644
--- a/rust/kernel/hrtimer/arc.rs
+++ b/rust/kernel/hrtimer/arc.rs
@@ -25,7 +25,7 @@ unsafe impl<U> TimerHandle for ArcTimerHandle<U>
U: HasTimer<U>,
{
fn cancel(&mut self) -> bool {
- let self_ptr = self.inner.as_ptr();
+ let self_ptr = Arc::as_ptr(&self.inner);
// SAFETY: As we obtained `self_ptr` from a valid reference
above, it
// must point to a valid `U`.
@@ -57,7 +57,7 @@ impl<U> TimerPointer for Arc<U>
fn schedule(self, expires: Ktime) -> ArcTimerHandle<U> {
// SAFETY: Since we generate the pointer passed to `schedule`
from a
// valid reference, it is a valid pointer.
- unsafe { U::schedule(self.as_ptr(), expires) };
+ unsafe { U::schedule(Arc::as_ptr(&self), expires) };
ArcTimerHandle { inner: self }
}
diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs
index 1466d9cd41652..0a314c2f4c5ea 100644
--- a/rust/kernel/sync/arc.rs
+++ b/rust/kernel/sync/arc.rs
@@ -259,8 +259,8 @@ pub fn into_raw(self) -> *const T {
}
/// Return a raw pointer to the data in this arc.
- pub fn as_ptr(&self) -> *const T {
- let ptr = self.ptr.as_ptr();
+ pub fn as_ptr(arc: &Self) -> *const T {
+ let ptr = arc.ptr.as_ptr();
// SAFETY: As we derive the pointer from a reference above,
the pointer
// must be valid.
unsafe { core::ptr::addr_of!((*ptr).data) }