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::prelude::*; 9 use crate::types::Opaque; 10 use pin_init; 11 12 mod arc; 13 pub mod aref; 14 pub mod atomic; 15 pub mod barrier; 16 pub mod completion; 17 mod condvar; 18 pub mod lock; 19 mod locked_by; 20 pub mod poll; 21 pub mod rcu; 22 mod refcount; 23 24 pub use arc::{Arc, ArcBorrow, UniqueArc}; 25 pub use completion::Completion; 26 pub use condvar::{new_condvar, CondVar, CondVarTimeoutResult}; 27 pub use lock::global::{global_lock, GlobalGuard, GlobalLock, GlobalLockBackend, GlobalLockedBy}; 28 pub use lock::mutex::{new_mutex, Mutex, MutexGuard}; 29 pub use lock::spinlock::{new_spinlock, SpinLock, SpinLockGuard}; 30 pub use locked_by::LockedBy; 31 pub use refcount::Refcount; 32 33 /// Represents a lockdep class. It's a wrapper around C's `lock_class_key`. 34 #[repr(transparent)] 35 #[pin_data(PinnedDrop)] 36 pub struct LockClassKey { 37 #[pin] 38 inner: Opaque<bindings::lock_class_key>, 39 } 40 41 // SAFETY: `bindings::lock_class_key` is designed to be used concurrently from multiple threads and 42 // provides its own synchronization. 43 unsafe impl Sync for LockClassKey {} 44 45 impl LockClassKey { 46 /// Initializes a dynamically allocated lock class key. In the common case of using a 47 /// statically allocated lock class key, the static_lock_class! macro should be used instead. 48 /// 49 /// # Examples 50 /// ``` 51 /// # use kernel::alloc::KBox; 52 /// # use kernel::types::ForeignOwnable; 53 /// # use kernel::sync::{LockClassKey, SpinLock}; 54 /// # use pin_init::stack_pin_init; 55 /// 56 /// let key = KBox::pin_init(LockClassKey::new_dynamic(), GFP_KERNEL)?; 57 /// let key_ptr = key.into_foreign(); 58 /// 59 /// { 60 /// stack_pin_init!(let num: SpinLock<u32> = SpinLock::new( 61 /// 0, 62 /// c"my_spinlock", 63 /// // SAFETY: `key_ptr` is returned by the above `into_foreign()`, whose 64 /// // `from_foreign()` has not yet been called. 65 /// unsafe { <Pin<KBox<LockClassKey>> as ForeignOwnable>::borrow(key_ptr) } 66 /// )); 67 /// } 68 /// 69 /// // SAFETY: We dropped `num`, the only use of the key, so the result of the previous 70 /// // `borrow` has also been dropped. Thus, it's safe to use from_foreign. 71 /// unsafe { drop(<Pin<KBox<LockClassKey>> as ForeignOwnable>::from_foreign(key_ptr)) }; 72 /// 73 /// # Ok::<(), Error>(()) 74 /// ``` 75 pub fn new_dynamic() -> impl PinInit<Self> { 76 pin_init!(Self { 77 // SAFETY: lockdep_register_key expects an uninitialized block of memory 78 inner <- Opaque::ffi_init(|slot| unsafe { bindings::lockdep_register_key(slot) }) 79 }) 80 } 81 82 pub(crate) fn as_ptr(&self) -> *mut bindings::lock_class_key { 83 self.inner.get() 84 } 85 } 86 87 #[pinned_drop] 88 impl PinnedDrop for LockClassKey { 89 fn drop(self: Pin<&mut Self>) { 90 // SAFETY: self.as_ptr was registered with lockdep and self is pinned, so the address 91 // hasn't changed. Thus, it's safe to pass to unregister. 92 unsafe { bindings::lockdep_unregister_key(self.as_ptr()) } 93 } 94 } 95 96 /// Defines a new static lock class and returns a pointer to it. 97 #[doc(hidden)] 98 #[macro_export] 99 macro_rules! static_lock_class { 100 () => {{ 101 static CLASS: $crate::sync::LockClassKey = 102 // Lockdep expects uninitialized memory when it's handed a statically allocated `struct 103 // lock_class_key`. 104 // 105 // SAFETY: `LockClassKey` transparently wraps `Opaque` which permits uninitialized 106 // memory. 107 unsafe { ::core::mem::MaybeUninit::uninit().assume_init() }; 108 $crate::prelude::Pin::static_ref(&CLASS) 109 }}; 110 } 111 112 /// Returns the given string, if one is provided, otherwise generates one based on the source code 113 /// location. 114 #[doc(hidden)] 115 #[macro_export] 116 macro_rules! optional_name { 117 () => { 118 $crate::c_str!(::core::concat!(::core::file!(), ":", ::core::line!())) 119 }; 120 ($name:literal) => { 121 $crate::c_str!($name) 122 }; 123 } 124