1 // SPDX-License-Identifier: GPL-2.0 1 // SPDX-License-Identifier: GPL-2.0
2 2
3 //! A condition variable. 3 //! A condition variable.
4 //! 4 //!
5 //! This module allows Rust code to use the ke 5 //! This module allows Rust code to use the kernel's [`struct wait_queue_head`] as a condition
6 //! variable. 6 //! variable.
7 7
8 use super::{lock::Backend, lock::Guard, LockCl 8 use super::{lock::Backend, lock::Guard, LockClassKey};
9 use crate::{ !! 9 use crate::{bindings, init::PinInit, pin_init, str::CStr, types::Opaque};
10 init::PinInit, <<
11 pin_init, <<
12 str::CStr, <<
13 task::{MAX_SCHEDULE_TIMEOUT, TASK_INTERRUP <<
14 time::Jiffies, <<
15 types::Opaque, <<
16 }; <<
17 use core::ffi::{c_int, c_long}; <<
18 use core::marker::PhantomPinned; 10 use core::marker::PhantomPinned;
19 use core::ptr; <<
20 use macros::pin_data; 11 use macros::pin_data;
21 12
22 /// Creates a [`CondVar`] initialiser with the 13 /// Creates a [`CondVar`] initialiser with the given name and a newly-created lock class.
23 #[macro_export] 14 #[macro_export]
24 macro_rules! new_condvar { 15 macro_rules! new_condvar {
25 ($($name:literal)?) => { 16 ($($name:literal)?) => {
26 $crate::sync::CondVar::new($crate::opt 17 $crate::sync::CondVar::new($crate::optional_name!($($name)?), $crate::static_lock_class!())
27 }; 18 };
28 } 19 }
29 pub use new_condvar; <<
30 20
31 /// A conditional variable. 21 /// A conditional variable.
32 /// 22 ///
33 /// Exposes the kernel's [`struct wait_queue_h 23 /// Exposes the kernel's [`struct wait_queue_head`] as a condition variable. It allows the caller to
34 /// atomically release the given lock and go t 24 /// atomically release the given lock and go to sleep. It reacquires the lock when it wakes up. And
35 /// it wakes up when notified by another threa 25 /// it wakes up when notified by another thread (via [`CondVar::notify_one`] or
36 /// [`CondVar::notify_all`]) or because the th 26 /// [`CondVar::notify_all`]) or because the thread received a signal. It may also wake up
37 /// spuriously. 27 /// spuriously.
38 /// 28 ///
39 /// Instances of [`CondVar`] need a lock class 29 /// Instances of [`CondVar`] need a lock class and to be pinned. The recommended way to create such
40 /// instances is with the [`pin_init`](crate:: 30 /// instances is with the [`pin_init`](crate::pin_init) and [`new_condvar`] macros.
41 /// 31 ///
42 /// # Examples 32 /// # Examples
43 /// 33 ///
44 /// The following is an example of using a con 34 /// The following is an example of using a condvar with a mutex:
45 /// 35 ///
46 /// ``` 36 /// ```
47 /// use kernel::sync::{new_condvar, new_mutex, !! 37 /// use kernel::sync::{CondVar, Mutex};
>> 38 /// use kernel::{new_condvar, new_mutex};
48 /// 39 ///
49 /// #[pin_data] 40 /// #[pin_data]
50 /// pub struct Example { 41 /// pub struct Example {
51 /// #[pin] 42 /// #[pin]
52 /// value: Mutex<u32>, 43 /// value: Mutex<u32>,
53 /// 44 ///
54 /// #[pin] 45 /// #[pin]
55 /// value_changed: CondVar, 46 /// value_changed: CondVar,
56 /// } 47 /// }
57 /// 48 ///
58 /// /// Waits for `e.value` to become `v`. 49 /// /// Waits for `e.value` to become `v`.
59 /// fn wait_for_value(e: &Example, v: u32) { 50 /// fn wait_for_value(e: &Example, v: u32) {
60 /// let mut guard = e.value.lock(); 51 /// let mut guard = e.value.lock();
61 /// while *guard != v { 52 /// while *guard != v {
62 /// e.value_changed.wait(&mut guard); 53 /// e.value_changed.wait(&mut guard);
63 /// } 54 /// }
64 /// } 55 /// }
65 /// 56 ///
66 /// /// Increments `e.value` and notifies all 57 /// /// Increments `e.value` and notifies all potential waiters.
67 /// fn increment(e: &Example) { 58 /// fn increment(e: &Example) {
68 /// *e.value.lock() += 1; 59 /// *e.value.lock() += 1;
69 /// e.value_changed.notify_all(); 60 /// e.value_changed.notify_all();
70 /// } 61 /// }
71 /// 62 ///
72 /// /// Allocates a new boxed `Example`. 63 /// /// Allocates a new boxed `Example`.
73 /// fn new_example() -> Result<Pin<Box<Example 64 /// fn new_example() -> Result<Pin<Box<Example>>> {
74 /// Box::pin_init(pin_init!(Example { 65 /// Box::pin_init(pin_init!(Example {
75 /// value <- new_mutex!(0), 66 /// value <- new_mutex!(0),
76 /// value_changed <- new_condvar!(), 67 /// value_changed <- new_condvar!(),
77 /// }), GFP_KERNEL) !! 68 /// }))
78 /// } 69 /// }
79 /// ``` 70 /// ```
80 /// 71 ///
81 /// [`struct wait_queue_head`]: srctree/includ 72 /// [`struct wait_queue_head`]: srctree/include/linux/wait.h
82 #[pin_data] 73 #[pin_data]
83 pub struct CondVar { 74 pub struct CondVar {
84 #[pin] 75 #[pin]
85 pub(crate) wait_queue_head: Opaque<binding !! 76 pub(crate) wait_list: Opaque<bindings::wait_queue_head>,
86 77
87 /// A condvar needs to be pinned because i 78 /// A condvar needs to be pinned because it contains a [`struct list_head`] that is
88 /// self-referential, so it cannot be safe 79 /// self-referential, so it cannot be safely moved once it is initialised.
89 /// <<
90 /// [`struct list_head`]: srctree/include/ <<
91 #[pin] 80 #[pin]
92 _pin: PhantomPinned, 81 _pin: PhantomPinned,
93 } 82 }
94 83
95 // SAFETY: `CondVar` only uses a `struct wait_ 84 // SAFETY: `CondVar` only uses a `struct wait_queue_head`, which is safe to use on any thread.
96 #[allow(clippy::non_send_fields_in_send_ty)] 85 #[allow(clippy::non_send_fields_in_send_ty)]
97 unsafe impl Send for CondVar {} 86 unsafe impl Send for CondVar {}
98 87
99 // SAFETY: `CondVar` only uses a `struct wait_ 88 // SAFETY: `CondVar` only uses a `struct wait_queue_head`, which is safe to use on multiple threads
100 // concurrently. 89 // concurrently.
101 unsafe impl Sync for CondVar {} 90 unsafe impl Sync for CondVar {}
102 91
103 impl CondVar { 92 impl CondVar {
104 /// Constructs a new condvar initialiser. 93 /// Constructs a new condvar initialiser.
105 pub fn new(name: &'static CStr, key: &'sta 94 pub fn new(name: &'static CStr, key: &'static LockClassKey) -> impl PinInit<Self> {
106 pin_init!(Self { 95 pin_init!(Self {
107 _pin: PhantomPinned, 96 _pin: PhantomPinned,
108 // SAFETY: `slot` is valid while t 97 // SAFETY: `slot` is valid while the closure is called and both `name` and `key` have
109 // static lifetimes so they live i 98 // static lifetimes so they live indefinitely.
110 wait_queue_head <- Opaque::ffi_ini !! 99 wait_list <- Opaque::ffi_init(|slot| unsafe {
111 bindings::__init_waitqueue_hea 100 bindings::__init_waitqueue_head(slot, name.as_char_ptr(), key.as_ptr())
112 }), 101 }),
113 }) 102 })
114 } 103 }
115 104
116 fn wait_internal<T: ?Sized, B: Backend>( !! 105 fn wait_internal<T: ?Sized, B: Backend>(&self, wait_state: u32, guard: &mut Guard<'_, T, B>) {
117 &self, <<
118 wait_state: c_int, <<
119 guard: &mut Guard<'_, T, B>, <<
120 timeout_in_jiffies: c_long, <<
121 ) -> c_long { <<
122 let wait = Opaque::<bindings::wait_que 106 let wait = Opaque::<bindings::wait_queue_entry>::uninit();
123 107
124 // SAFETY: `wait` points to valid memo 108 // SAFETY: `wait` points to valid memory.
125 unsafe { bindings::init_wait(wait.get( 109 unsafe { bindings::init_wait(wait.get()) };
126 110
127 // SAFETY: Both `wait` and `wait_queue !! 111 // SAFETY: Both `wait` and `wait_list` point to valid memory.
128 unsafe { 112 unsafe {
129 bindings::prepare_to_wait_exclusiv !! 113 bindings::prepare_to_wait_exclusive(self.wait_list.get(), wait.get(), wait_state as _)
130 }; 114 };
131 115
132 // SAFETY: Switches to another thread. !! 116 // SAFETY: No arguments, switches to another thread.
133 let ret = guard.do_unlocked(|| unsafe !! 117 guard.do_unlocked(|| unsafe { bindings::schedule() });
134 <<
135 // SAFETY: Both `wait` and `wait_queue <<
136 unsafe { bindings::finish_wait(self.wa <<
137 118
138 ret !! 119 // SAFETY: Both `wait` and `wait_list` point to valid memory.
>> 120 unsafe { bindings::finish_wait(self.wait_list.get(), wait.get()) };
139 } 121 }
140 122
141 /// Releases the lock and waits for a noti 123 /// Releases the lock and waits for a notification in uninterruptible mode.
142 /// 124 ///
143 /// Atomically releases the given lock (wh 125 /// Atomically releases the given lock (whose ownership is proven by the guard) and puts the
144 /// thread to sleep, reacquiring the lock 126 /// thread to sleep, reacquiring the lock on wake up. It wakes up when notified by
145 /// [`CondVar::notify_one`] or [`CondVar:: 127 /// [`CondVar::notify_one`] or [`CondVar::notify_all`]. Note that it may also wake up
146 /// spuriously. 128 /// spuriously.
147 pub fn wait<T: ?Sized, B: Backend>(&self, 129 pub fn wait<T: ?Sized, B: Backend>(&self, guard: &mut Guard<'_, T, B>) {
148 self.wait_internal(TASK_UNINTERRUPTIBL !! 130 self.wait_internal(bindings::TASK_UNINTERRUPTIBLE, guard);
149 } 131 }
150 132
151 /// Releases the lock and waits for a noti 133 /// Releases the lock and waits for a notification in interruptible mode.
152 /// 134 ///
153 /// Similar to [`CondVar::wait`], except t 135 /// Similar to [`CondVar::wait`], except that the wait is interruptible. That is, the thread may
154 /// wake up due to signals. It may also wa 136 /// wake up due to signals. It may also wake up spuriously.
155 /// 137 ///
156 /// Returns whether there is a signal pend 138 /// Returns whether there is a signal pending.
157 #[must_use = "wait_interruptible returns i 139 #[must_use = "wait_interruptible returns if a signal is pending, so the caller must check the return value"]
158 pub fn wait_interruptible<T: ?Sized, B: Ba 140 pub fn wait_interruptible<T: ?Sized, B: Backend>(&self, guard: &mut Guard<'_, T, B>) -> bool {
159 self.wait_internal(TASK_INTERRUPTIBLE, !! 141 self.wait_internal(bindings::TASK_INTERRUPTIBLE, guard);
160 crate::current!().signal_pending() 142 crate::current!().signal_pending()
161 } 143 }
162 144
163 /// Releases the lock and waits for a noti !! 145 /// Calls the kernel function to notify the appropriate number of threads with the given flags.
164 /// !! 146 fn notify(&self, count: i32, flags: u32) {
165 /// Atomically releases the given lock (wh !! 147 // SAFETY: `wait_list` points to valid memory.
166 /// thread to sleep. It wakes up when noti <<
167 /// [`CondVar::notify_all`], or when a tim <<
168 #[must_use = "wait_interruptible_timeout r <<
169 pub fn wait_interruptible_timeout<T: ?Size <<
170 &self, <<
171 guard: &mut Guard<'_, T, B>, <<
172 jiffies: Jiffies, <<
173 ) -> CondVarTimeoutResult { <<
174 let jiffies = jiffies.try_into().unwra <<
175 let res = self.wait_internal(TASK_INTE <<
176 <<
177 match (res as Jiffies, crate::current! <<
178 (jiffies, true) => CondVarTimeoutR <<
179 (0, false) => CondVarTimeoutResult <<
180 (jiffies, false) => CondVarTimeout <<
181 } <<
182 } <<
183 <<
184 /// Calls the kernel function to notify th <<
185 fn notify(&self, count: c_int) { <<
186 // SAFETY: `wait_queue_head` points to <<
187 unsafe { 148 unsafe {
188 bindings::__wake_up( 149 bindings::__wake_up(
189 self.wait_queue_head.get(), !! 150 self.wait_list.get(),
190 TASK_NORMAL, !! 151 bindings::TASK_NORMAL,
191 count, 152 count,
192 ptr::null_mut(), !! 153 flags as _,
193 ) 154 )
194 }; 155 };
195 } 156 }
196 157
197 /// Calls the kernel function to notify on <<
198 /// <<
199 /// This method behaves like `notify_one`, <<
200 /// current thread is about to go to sleep <<
201 /// CPU. <<
202 pub fn notify_sync(&self) { <<
203 // SAFETY: `wait_queue_head` points to <<
204 unsafe { bindings::__wake_up_sync(self <<
205 } <<
206 <<
207 /// Wakes a single waiter up, if any. 158 /// Wakes a single waiter up, if any.
208 /// 159 ///
209 /// This is not 'sticky' in the sense that 160 /// This is not 'sticky' in the sense that if no thread is waiting, the notification is lost
210 /// completely (as opposed to automaticall 161 /// completely (as opposed to automatically waking up the next waiter).
211 pub fn notify_one(&self) { 162 pub fn notify_one(&self) {
212 self.notify(1); !! 163 self.notify(1, 0);
213 } 164 }
214 165
215 /// Wakes all waiters up, if any. 166 /// Wakes all waiters up, if any.
216 /// 167 ///
217 /// This is not 'sticky' in the sense that 168 /// This is not 'sticky' in the sense that if no thread is waiting, the notification is lost
218 /// completely (as opposed to automaticall 169 /// completely (as opposed to automatically waking up the next waiter).
219 pub fn notify_all(&self) { 170 pub fn notify_all(&self) {
220 self.notify(0); !! 171 self.notify(0, 0);
221 } 172 }
222 } <<
223 <<
224 /// The return type of `wait_timeout`. <<
225 pub enum CondVarTimeoutResult { <<
226 /// The timeout was reached. <<
227 Timeout, <<
228 /// Somebody woke us up. <<
229 Woken { <<
230 /// Remaining sleep duration. <<
231 jiffies: Jiffies, <<
232 }, <<
233 /// A signal occurred. <<
234 Signal { <<
235 /// Remaining sleep duration. <<
236 jiffies: Jiffies, <<
237 }, <<
238 } 173 }
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