1 // SPDX-License-Identifier: GPL-2.0 2 3 //! Synchronisation primitives. 4 //! 5 //! This module contains the kernel APIs related to synchronisation that have been ported or 6 //! wrapped for usage by Rust code in the kernel. 7 8 use crate::pin_init; 9 use crate::prelude::*; 10 use crate::types::Opaque; 11 12 mod arc; 13 mod condvar; 14 pub mod lock; 15 mod locked_by; 16 pub mod poll; 17 pub mod rcu; 18 19 pub use arc::{Arc, ArcBorrow, UniqueArc}; 20 pub use condvar::{new_condvar, CondVar, CondVarTimeoutResult}; 21 pub use lock::global::{global_lock, GlobalGuard, GlobalLock, GlobalLockBackend, GlobalLockedBy}; 22 pub use lock::mutex::{new_mutex, Mutex, MutexGuard}; 23 pub use lock::spinlock::{new_spinlock, SpinLock, SpinLockGuard}; 24 pub use locked_by::LockedBy; 25 26 /// Represents a lockdep class. It's a wrapper around C's `lock_class_key`. 27 #[repr(transparent)] 28 #[pin_data(PinnedDrop)] 29 pub struct LockClassKey { 30 #[pin] 31 inner: Opaque<bindings::lock_class_key>, 32 } 33 34 // SAFETY: `bindings::lock_class_key` is designed to be used concurrently from multiple threads and 35 // provides its own synchronization. 36 unsafe impl Sync for LockClassKey {} 37 38 impl LockClassKey { 39 /// Initializes a dynamically allocated lock class key. In the common case of using a 40 /// statically allocated lock class key, the static_lock_class! macro should be used instead. 41 /// 42 /// # Example 43 /// ``` 44 /// # use kernel::{c_str, stack_pin_init}; 45 /// # use kernel::alloc::KBox; 46 /// # use kernel::types::ForeignOwnable; 47 /// # use kernel::sync::{LockClassKey, SpinLock}; 48 /// 49 /// let key = KBox::pin_init(LockClassKey::new_dynamic(), GFP_KERNEL)?; 50 /// let key_ptr = key.into_foreign(); 51 /// 52 /// { 53 /// stack_pin_init!(let num: SpinLock<u32> = SpinLock::new( 54 /// 0, 55 /// c_str!("my_spinlock"), 56 /// // SAFETY: `key_ptr` is returned by the above `into_foreign()`, whose 57 /// // `from_foreign()` has not yet been called. 58 /// unsafe { <Pin<KBox<LockClassKey>> as ForeignOwnable>::borrow(key_ptr) } 59 /// )); 60 /// } 61 /// 62 /// // SAFETY: We dropped `num`, the only use of the key, so the result of the previous 63 /// // `borrow` has also been dropped. Thus, it's safe to use from_foreign. 64 /// unsafe { drop(<Pin<KBox<LockClassKey>> as ForeignOwnable>::from_foreign(key_ptr)) }; 65 /// 66 /// # Ok::<(), Error>(()) 67 /// ``` new_dynamic() -> impl PinInit<Self>68 pub fn new_dynamic() -> impl PinInit<Self> { 69 pin_init!(Self { 70 // SAFETY: lockdep_register_key expects an uninitialized block of memory 71 inner <- Opaque::ffi_init(|slot| unsafe { bindings::lockdep_register_key(slot) }) 72 }) 73 } 74 as_ptr(&self) -> *mut bindings::lock_class_key75 pub(crate) fn as_ptr(&self) -> *mut bindings::lock_class_key { 76 self.inner.get() 77 } 78 } 79 80 #[pinned_drop] 81 impl PinnedDrop for LockClassKey { drop(self: Pin<&mut Self>)82 fn drop(self: Pin<&mut Self>) { 83 // SAFETY: self.as_ptr was registered with lockdep and self is pinned, so the address 84 // hasn't changed. Thus, it's safe to pass to unregister. 85 unsafe { bindings::lockdep_unregister_key(self.as_ptr()) } 86 } 87 } 88 89 /// Defines a new static lock class and returns a pointer to it. 90 #[doc(hidden)] 91 #[macro_export] 92 macro_rules! static_lock_class { 93 () => {{ 94 static CLASS: $crate::sync::LockClassKey = 95 // SAFETY: lockdep expects uninitialized memory when it's handed a statically allocated 96 // lock_class_key 97 unsafe { ::core::mem::MaybeUninit::uninit().assume_init() }; 98 $crate::prelude::Pin::static_ref(&CLASS) 99 }}; 100 } 101 102 /// Returns the given string, if one is provided, otherwise generates one based on the source code 103 /// location. 104 #[doc(hidden)] 105 #[macro_export] 106 macro_rules! optional_name { 107 () => { 108 $crate::c_str!(::core::concat!(::core::file!(), ":", ::core::line!())) 109 }; 110 ($name:literal) => { 111 $crate::c_str!($name) 112 }; 113 } 114