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::alloc::KBox; 54 /// # use kernel::types::ForeignOwnable; 55 /// # use kernel::sync::{LockClassKey, SpinLock}; 56 /// # use pin_init::stack_pin_init; 57 /// 58 /// let key = KBox::pin_init(LockClassKey::new_dynamic(), GFP_KERNEL)?; 59 /// let key_ptr = key.into_foreign(); 60 /// 61 /// { 62 /// stack_pin_init!(let num: SpinLock<u32> = SpinLock::new( 63 /// 0, 64 /// c"my_spinlock", 65 /// // SAFETY: `key_ptr` is returned by the above `into_foreign()`, whose 66 /// // `from_foreign()` has not yet been called. 67 /// unsafe { <Pin<KBox<LockClassKey>> as ForeignOwnable>::borrow(key_ptr) } 68 /// )); 69 /// } 70 /// 71 /// // SAFETY: We dropped `num`, the only use of the key, so the result of the previous 72 /// // `borrow` has also been dropped. Thus, it's safe to use from_foreign. 73 /// unsafe { drop(<Pin<KBox<LockClassKey>> as ForeignOwnable>::from_foreign(key_ptr)) }; 74 /// 75 /// # Ok::<(), Error>(()) 76 /// ``` new_dynamic() -> impl PinInit<Self>77 pub fn new_dynamic() -> impl PinInit<Self> { 78 pin_init!(Self { 79 // SAFETY: lockdep_register_key expects an uninitialized block of memory 80 inner <- Opaque::ffi_init(|slot| unsafe { bindings::lockdep_register_key(slot) }) 81 }) 82 } 83 as_ptr(&self) -> *mut bindings::lock_class_key84 pub(crate) fn as_ptr(&self) -> *mut bindings::lock_class_key { 85 self.inner.get() 86 } 87 } 88 89 #[pinned_drop] 90 impl PinnedDrop for LockClassKey { drop(self: Pin<&mut Self>)91 fn drop(self: Pin<&mut Self>) { 92 // SAFETY: self.as_ptr was registered with lockdep and self is pinned, so the address 93 // hasn't changed. Thus, it's safe to pass to unregister. 94 unsafe { bindings::lockdep_unregister_key(self.as_ptr()) } 95 } 96 } 97 98 /// Defines a new static lock class and returns a pointer to it. 99 #[doc(hidden)] 100 #[macro_export] 101 macro_rules! static_lock_class { 102 () => {{ 103 static CLASS: $crate::sync::LockClassKey = 104 // Lockdep expects uninitialized memory when it's handed a statically allocated `struct 105 // lock_class_key`. 106 // 107 // SAFETY: `LockClassKey` transparently wraps `Opaque` which permits uninitialized 108 // memory. 109 unsafe { ::core::mem::MaybeUninit::uninit().assume_init() }; 110 $crate::prelude::Pin::static_ref(&CLASS) 111 }}; 112 } 113 114 /// Returns the given string, if one is provided, otherwise generates one based on the source code 115 /// location. 116 #[doc(hidden)] 117 #[macro_export] 118 macro_rules! optional_name { 119 () => { 120 $crate::c_str!(::core::concat!(::core::file!(), ":", ::core::line!())) 121 }; 122 ($name:literal) => { 123 $crate::c_str!($name) 124 }; 125 } 126