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// SPDX-License-Identifier: GPL-2.0
//! Synchronisation primitives.
//!
//! This module contains the kernel APIs related to synchronisation that have been ported or
//! wrapped for usage by Rust code in the kernel.
use crate::prelude::*;
use crate::types::Opaque;
use pin_init;
mod arc;
mod condvar;
pub mod lock;
mod locked_by;
pub mod poll;
pub mod rcu;
pub use arc::{Arc, ArcBorrow, UniqueArc};
pub use condvar::{new_condvar, CondVar, CondVarTimeoutResult};
pub use lock::global::{global_lock, GlobalGuard, GlobalLock, GlobalLockBackend, GlobalLockedBy};
pub use lock::mutex::{new_mutex, Mutex, MutexGuard};
pub use lock::spinlock::{new_spinlock, SpinLock, SpinLockGuard};
pub use locked_by::LockedBy;
/// Represents a lockdep class. It's a wrapper around C's `lock_class_key`.
#[repr(transparent)]
#[pin_data(PinnedDrop)]
pub struct LockClassKey {
#[pin]
inner: Opaque<bindings::lock_class_key>,
}
// SAFETY: `bindings::lock_class_key` is designed to be used concurrently from multiple threads and
// provides its own synchronization.
unsafe impl Sync for LockClassKey {}
impl LockClassKey {
/// Initializes a dynamically allocated lock class key. In the common case of using a
/// statically allocated lock class key, the static_lock_class! macro should be used instead.
///
/// # Example
/// ```
/// # use kernel::c_str;
/// # use kernel::alloc::KBox;
/// # use kernel::types::ForeignOwnable;
/// # use kernel::sync::{LockClassKey, SpinLock};
/// # use pin_init::stack_pin_init;
///
/// let key = KBox::pin_init(LockClassKey::new_dynamic(), GFP_KERNEL)?;
/// let key_ptr = key.into_foreign();
///
/// {
/// stack_pin_init!(let num: SpinLock<u32> = SpinLock::new(
/// 0,
/// c_str!("my_spinlock"),
/// // SAFETY: `key_ptr` is returned by the above `into_foreign()`, whose
/// // `from_foreign()` has not yet been called.
/// unsafe { <Pin<KBox<LockClassKey>> as ForeignOwnable>::borrow(key_ptr) }
/// ));
/// }
///
/// // SAFETY: We dropped `num`, the only use of the key, so the result of the previous
/// // `borrow` has also been dropped. Thus, it's safe to use from_foreign.
/// unsafe { drop(<Pin<KBox<LockClassKey>> as ForeignOwnable>::from_foreign(key_ptr)) };
///
/// # Ok::<(), Error>(())
/// ```
pub fn new_dynamic() -> impl PinInit<Self> {
pin_init!(Self {
// SAFETY: lockdep_register_key expects an uninitialized block of memory
inner <- Opaque::ffi_init(|slot| unsafe { bindings::lockdep_register_key(slot) })
})
}
pub(crate) fn as_ptr(&self) -> *mut bindings::lock_class_key {
self.inner.get()
}
}
#[pinned_drop]
impl PinnedDrop for LockClassKey {
fn drop(self: Pin<&mut Self>) {
// SAFETY: self.as_ptr was registered with lockdep and self is pinned, so the address
// hasn't changed. Thus, it's safe to pass to unregister.
unsafe { bindings::lockdep_unregister_key(self.as_ptr()) }
}
}
/// Defines a new static lock class and returns a pointer to it.
#[doc(hidden)]
#[macro_export]
macro_rules! static_lock_class {
() => {{
static CLASS: $crate::sync::LockClassKey =
// SAFETY: lockdep expects uninitialized memory when it's handed a statically allocated
// lock_class_key
unsafe { ::core::mem::MaybeUninit::uninit().assume_init() };
$crate::prelude::Pin::static_ref(&CLASS)
}};
}
/// Returns the given string, if one is provided, otherwise generates one based on the source code
/// location.
#[doc(hidden)]
#[macro_export]
macro_rules! optional_name {
() => {
$crate::c_str!(::core::concat!(::core::file!(), ":", ::core::line!()))
};
($name:literal) => {
$crate::c_str!($name)
};
}
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