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 completion; 14 mod condvar; 15 pub mod lock; 16 mod locked_by; 17 pub mod poll; 18 pub mod rcu; 19 20 pub use arc::{Arc, ArcBorrow, UniqueArc}; 21 pub use completion::Completion; 22 pub use condvar::{new_condvar, CondVar, CondVarTimeoutResult}; 23 pub use lock::global::{global_lock, GlobalGuard, GlobalLock, GlobalLockBackend, GlobalLockedBy}; 24 pub use lock::mutex::{new_mutex, Mutex, MutexGuard}; 25 pub use lock::spinlock::{new_spinlock, SpinLock, SpinLockGuard}; 26 pub use locked_by::LockedBy; 27 28 /// Represents a lockdep class. It's a wrapper around C's `lock_class_key`. 29 #[repr(transparent)] 30 #[pin_data(PinnedDrop)] 31 pub struct LockClassKey { 32 #[pin] 33 inner: Opaque<bindings::lock_class_key>, 34 } 35 36 // SAFETY: `bindings::lock_class_key` is designed to be used concurrently from multiple threads and 37 // provides its own synchronization. 38 unsafe impl Sync for LockClassKey {} 39 40 impl LockClassKey { 41 /// Initializes a dynamically allocated lock class key. In the common case of using a 42 /// statically allocated lock class key, the static_lock_class! macro should be used instead. 43 /// 44 /// # Example 45 /// ``` 46 /// # use kernel::c_str; 47 /// # use kernel::alloc::KBox; 48 /// # use kernel::types::ForeignOwnable; 49 /// # use kernel::sync::{LockClassKey, SpinLock}; 50 /// # use pin_init::stack_pin_init; 51 /// 52 /// let key = KBox::pin_init(LockClassKey::new_dynamic(), GFP_KERNEL)?; 53 /// let key_ptr = key.into_foreign(); 54 /// 55 /// { 56 /// stack_pin_init!(let num: SpinLock<u32> = SpinLock::new( 57 /// 0, 58 /// c_str!("my_spinlock"), 59 /// // SAFETY: `key_ptr` is returned by the above `into_foreign()`, whose 60 /// // `from_foreign()` has not yet been called. 61 /// unsafe { <Pin<KBox<LockClassKey>> as ForeignOwnable>::borrow(key_ptr) } 62 /// )); 63 /// } 64 /// 65 /// // SAFETY: We dropped `num`, the only use of the key, so the result of the previous 66 /// // `borrow` has also been dropped. Thus, it's safe to use from_foreign. 67 /// unsafe { drop(<Pin<KBox<LockClassKey>> as ForeignOwnable>::from_foreign(key_ptr)) }; 68 /// 69 /// # Ok::<(), Error>(()) 70 /// ``` new_dynamic() -> impl PinInit<Self>71 pub fn new_dynamic() -> impl PinInit<Self> { 72 pin_init!(Self { 73 // SAFETY: lockdep_register_key expects an uninitialized block of memory 74 inner <- Opaque::ffi_init(|slot| unsafe { bindings::lockdep_register_key(slot) }) 75 }) 76 } 77 as_ptr(&self) -> *mut bindings::lock_class_key78 pub(crate) fn as_ptr(&self) -> *mut bindings::lock_class_key { 79 self.inner.get() 80 } 81 } 82 83 #[pinned_drop] 84 impl PinnedDrop for LockClassKey { drop(self: Pin<&mut Self>)85 fn drop(self: Pin<&mut Self>) { 86 // SAFETY: self.as_ptr was registered with lockdep and self is pinned, so the address 87 // hasn't changed. Thus, it's safe to pass to unregister. 88 unsafe { bindings::lockdep_unregister_key(self.as_ptr()) } 89 } 90 } 91 92 /// Defines a new static lock class and returns a pointer to it. 93 #[doc(hidden)] 94 #[macro_export] 95 macro_rules! static_lock_class { 96 () => {{ 97 static CLASS: $crate::sync::LockClassKey = 98 // SAFETY: lockdep expects uninitialized memory when it's handed a statically allocated 99 // lock_class_key 100 unsafe { ::core::mem::MaybeUninit::uninit().assume_init() }; 101 $crate::prelude::Pin::static_ref(&CLASS) 102 }}; 103 } 104 105 /// Returns the given string, if one is provided, otherwise generates one based on the source code 106 /// location. 107 #[doc(hidden)] 108 #[macro_export] 109 macro_rules! optional_name { 110 () => { 111 $crate::c_str!(::core::concat!(::core::file!(), ":", ::core::line!())) 112 }; 113 ($name:literal) => { 114 $crate::c_str!($name) 115 }; 116 } 117