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 mod set_once; 24 25 pub use arc::{Arc, ArcBorrow, UniqueArc}; 26 pub use completion::Completion; 27 pub use condvar::{new_condvar, CondVar, CondVarTimeoutResult}; 28 pub use lock::global::{global_lock, GlobalGuard, GlobalLock, GlobalLockBackend, GlobalLockedBy}; 29 pub use lock::mutex::{new_mutex, Mutex, MutexGuard}; 30 pub use lock::spinlock::{new_spinlock, SpinLock, SpinLockGuard}; 31 pub use locked_by::LockedBy; 32 pub use refcount::Refcount; 33 pub use set_once::SetOnce; 34 35 /// Represents a lockdep class. It's a wrapper around C's `lock_class_key`. 36 #[repr(transparent)] 37 #[pin_data(PinnedDrop)] 38 pub struct LockClassKey { 39 #[pin] 40 inner: Opaque<bindings::lock_class_key>, 41 } 42 43 // SAFETY: `bindings::lock_class_key` is designed to be used concurrently from multiple threads and 44 // provides its own synchronization. 45 unsafe impl Sync for LockClassKey {} 46 47 impl LockClassKey { 48 /// Initializes a dynamically allocated lock class key. In the common case of using a 49 /// statically allocated lock class key, the static_lock_class! macro should be used instead. 50 /// 51 /// # Examples 52 /// ``` 53 /// # use kernel::c_str; 54 /// # use kernel::alloc::KBox; 55 /// # use kernel::types::ForeignOwnable; 56 /// # use kernel::sync::{LockClassKey, SpinLock}; 57 /// # use pin_init::stack_pin_init; 58 /// 59 /// let key = KBox::pin_init(LockClassKey::new_dynamic(), GFP_KERNEL)?; 60 /// let key_ptr = key.into_foreign(); 61 /// 62 /// { 63 /// stack_pin_init!(let num: SpinLock<u32> = SpinLock::new( 64 /// 0, 65 /// c_str!("my_spinlock"), 66 /// // SAFETY: `key_ptr` is returned by the above `into_foreign()`, whose 67 /// // `from_foreign()` has not yet been called. 68 /// unsafe { <Pin<KBox<LockClassKey>> as ForeignOwnable>::borrow(key_ptr) } 69 /// )); 70 /// } 71 /// 72 /// // SAFETY: We dropped `num`, the only use of the key, so the result of the previous 73 /// // `borrow` has also been dropped. Thus, it's safe to use from_foreign. 74 /// unsafe { drop(<Pin<KBox<LockClassKey>> as ForeignOwnable>::from_foreign(key_ptr)) }; 75 /// 76 /// # Ok::<(), Error>(()) 77 /// ``` 78 pub fn new_dynamic() -> impl PinInit<Self> { 79 pin_init!(Self { 80 // SAFETY: lockdep_register_key expects an uninitialized block of memory 81 inner <- Opaque::ffi_init(|slot| unsafe { bindings::lockdep_register_key(slot) }) 82 }) 83 } 84 85 pub(crate) fn as_ptr(&self) -> *mut bindings::lock_class_key { 86 self.inner.get() 87 } 88 } 89 90 #[pinned_drop] 91 impl PinnedDrop for LockClassKey { 92 fn drop(self: Pin<&mut Self>) { 93 // SAFETY: self.as_ptr was registered with lockdep and self is pinned, so the address 94 // hasn't changed. Thus, it's safe to pass to unregister. 95 unsafe { bindings::lockdep_unregister_key(self.as_ptr()) } 96 } 97 } 98 99 /// Defines a new static lock class and returns a pointer to it. 100 #[doc(hidden)] 101 #[macro_export] 102 macro_rules! static_lock_class { 103 () => {{ 104 static CLASS: $crate::sync::LockClassKey = 105 // Lockdep expects uninitialized memory when it's handed a statically allocated `struct 106 // lock_class_key`. 107 // 108 // SAFETY: `LockClassKey` transparently wraps `Opaque` which permits uninitialized 109 // memory. 110 unsafe { ::core::mem::MaybeUninit::uninit().assume_init() }; 111 $crate::prelude::Pin::static_ref(&CLASS) 112 }}; 113 } 114 115 /// Returns the given string, if one is provided, otherwise generates one based on the source code 116 /// location. 117 #[doc(hidden)] 118 #[macro_export] 119 macro_rules! optional_name { 120 () => { 121 $crate::c_str!(::core::concat!(::core::file!(), ":", ::core::line!())) 122 }; 123 ($name:literal) => { 124 $crate::c_str!($name) 125 }; 126 } 127