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 completion; 15 mod condvar; 16 pub mod lock; 17 mod locked_by; 18 pub mod poll; 19 pub mod rcu; 20 21 pub use arc::{Arc, ArcBorrow, UniqueArc}; 22 pub use completion::Completion; 23 pub use condvar::{new_condvar, CondVar, CondVarTimeoutResult}; 24 pub use lock::global::{global_lock, GlobalGuard, GlobalLock, GlobalLockBackend, GlobalLockedBy}; 25 pub use lock::mutex::{new_mutex, Mutex, MutexGuard}; 26 pub use lock::spinlock::{new_spinlock, SpinLock, SpinLockGuard}; 27 pub use locked_by::LockedBy; 28 29 /// Represents a lockdep class. It's a wrapper around C's `lock_class_key`. 30 #[repr(transparent)] 31 #[pin_data(PinnedDrop)] 32 pub struct LockClassKey { 33 #[pin] 34 inner: Opaque<bindings::lock_class_key>, 35 } 36 37 // SAFETY: `bindings::lock_class_key` is designed to be used concurrently from multiple threads and 38 // provides its own synchronization. 39 unsafe impl Sync for LockClassKey {} 40 41 impl LockClassKey { 42 /// Initializes a dynamically allocated lock class key. In the common case of using a 43 /// statically allocated lock class key, the static_lock_class! macro should be used instead. 44 /// 45 /// # Examples 46 /// ``` 47 /// # use kernel::c_str; 48 /// # use kernel::alloc::KBox; 49 /// # use kernel::types::ForeignOwnable; 50 /// # use kernel::sync::{LockClassKey, SpinLock}; 51 /// # use pin_init::stack_pin_init; 52 /// 53 /// let key = KBox::pin_init(LockClassKey::new_dynamic(), GFP_KERNEL)?; 54 /// let key_ptr = key.into_foreign(); 55 /// 56 /// { 57 /// stack_pin_init!(let num: SpinLock<u32> = SpinLock::new( 58 /// 0, 59 /// c_str!("my_spinlock"), 60 /// // SAFETY: `key_ptr` is returned by the above `into_foreign()`, whose 61 /// // `from_foreign()` has not yet been called. 62 /// unsafe { <Pin<KBox<LockClassKey>> as ForeignOwnable>::borrow(key_ptr) } 63 /// )); 64 /// } 65 /// 66 /// // SAFETY: We dropped `num`, the only use of the key, so the result of the previous 67 /// // `borrow` has also been dropped. Thus, it's safe to use from_foreign. 68 /// unsafe { drop(<Pin<KBox<LockClassKey>> as ForeignOwnable>::from_foreign(key_ptr)) }; 69 /// 70 /// # Ok::<(), Error>(()) 71 /// ``` new_dynamic() -> impl PinInit<Self>72 pub fn new_dynamic() -> impl PinInit<Self> { 73 pin_init!(Self { 74 // SAFETY: lockdep_register_key expects an uninitialized block of memory 75 inner <- Opaque::ffi_init(|slot| unsafe { bindings::lockdep_register_key(slot) }) 76 }) 77 } 78 as_ptr(&self) -> *mut bindings::lock_class_key79 pub(crate) fn as_ptr(&self) -> *mut bindings::lock_class_key { 80 self.inner.get() 81 } 82 } 83 84 #[pinned_drop] 85 impl PinnedDrop for LockClassKey { drop(self: Pin<&mut Self>)86 fn drop(self: Pin<&mut Self>) { 87 // SAFETY: self.as_ptr was registered with lockdep and self is pinned, so the address 88 // hasn't changed. Thus, it's safe to pass to unregister. 89 unsafe { bindings::lockdep_unregister_key(self.as_ptr()) } 90 } 91 } 92 93 /// Defines a new static lock class and returns a pointer to it. 94 #[doc(hidden)] 95 #[macro_export] 96 macro_rules! static_lock_class { 97 () => {{ 98 static CLASS: $crate::sync::LockClassKey = 99 // Lockdep expects uninitialized memory when it's handed a statically allocated `struct 100 // lock_class_key`. 101 // 102 // SAFETY: `LockClassKey` transparently wraps `Opaque` which permits uninitialized 103 // memory. 104 unsafe { ::core::mem::MaybeUninit::uninit().assume_init() }; 105 $crate::prelude::Pin::static_ref(&CLASS) 106 }}; 107 } 108 109 /// Returns the given string, if one is provided, otherwise generates one based on the source code 110 /// location. 111 #[doc(hidden)] 112 #[macro_export] 113 macro_rules! optional_name { 114 () => { 115 $crate::c_str!(::core::concat!(::core::file!(), ":", ::core::line!())) 116 }; 117 ($name:literal) => { 118 $crate::c_str!($name) 119 }; 120 } 121