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Add read_with methods to RCU types

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Zhang Junyang 2025-03-18 19:13:57 +08:00 committed by Tate, Hongliang Tian
parent 79a965374d
commit 244a34a2fc
1 changed files with 43 additions and 0 deletions
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43
ostd/src/sync/rcu/mod.rs
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@ -168,6 +168,22 @@ impl<P: OwnerPtr> RcuInner<P> {
_inner_guard: guard,
}
}
fn read_with<'a>(
&'a self,
_guard: &'a DisabledPreemptGuard,
) -> Option<&'a <P as OwnerPtr>::Target> {
let obj_ptr = self.ptr.load(Acquire);
if obj_ptr.is_null() {
return None;
}
// SAFETY:
// 1. This pointer is not NULL.
// 2. Since the preemption is disabled, the pointer is valid because
// other writers won't release the allocation until this task passes
// the quiescent state.
Some(unsafe { &*obj_ptr })
}
}
impl<P: OwnerPtr> Drop for RcuInner<P> {
@ -250,6 +266,18 @@ impl<P: OwnerPtr> Rcu<P> {
pub fn read(&self) -> RcuReadGuard<'_, P> {
RcuReadGuard(self.0.read())
}
/// Reads the RCU-protected value given that preemption is already disabled.
///
/// If preemption is already disabled, this function can reduce the
/// overhead of disabling preemption again.
///
/// Unlike [`Self::read`], this function does not return a read guard, so
/// you cannot use [`RcuReadGuard::compare_exchange`] to synchronize the
/// writers. You may do it via a [`super::SpinLock`].
pub fn read_with<'a>(&'a self, guard: &'a DisabledPreemptGuard) -> &'a <P as OwnerPtr>::Target {
self.0.read_with(guard).unwrap()
}
}
impl<P: OwnerPtr> RcuOption<P> {
@ -292,6 +320,21 @@ impl<P: OwnerPtr> RcuOption<P> {
pub fn read(&self) -> RcuOptionReadGuard<'_, P> {
RcuOptionReadGuard(self.0.read())
}
/// Reads the RCU-protected value given that preemption is already disabled.
///
/// If preemption is already disabled, this function can reduce the
/// overhead of disabling preemption again.
///
/// Unlike [`Self::read`], this function does not return a read guard, so
/// you cannot use [`RcuOptionReadGuard::compare_exchange`] to synchronize the
/// writers. You may do it via a [`super::SpinLock`].
pub fn read_with<'a>(
&'a self,
guard: &'a DisabledPreemptGuard,
) -> Option<&'a <P as OwnerPtr>::Target> {
self.0.read_with(guard)
}
}
// RCU guards that have a non-null pointer can be directly dereferenced.