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