1 /* 2 * Copyright (c) 2025 Google Inc. All rights reserved 3 * 4 * Permission is hereby granted, free of charge, to any person obtaining 5 * a copy of this software and associated documentation files 6 * (the "Software"), to deal in the Software without restriction, 7 * including without limitation the rights to use, copy, modify, merge, 8 * publish, distribute, sublicense, and/or sell copies of the Software, 9 * and to permit persons to whom the Software is furnished to do so, 10 * subject to the following conditions: 11 * 12 * The above copyright notice and this permission notice shall be 13 * included in all copies or substantial portions of the Software. 14 * 15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 16 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 17 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. 18 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY 19 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, 20 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE 21 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. 22 */ 23 24 use crate::sys::{event_init, event_signal, event_wait_timeout}; 25 use crate::sys::{event_t, status_t, uint}; 26 use crate::INFINITE_TIME; 27 use alloc::boxed::Box; 28 use core::cell::UnsafeCell; 29 use core::mem; 30 31 pub use crate::sys::EVENT_FLAG_AUTOUNSIGNAL; 32 33 // `event_t`s should not move since they contain wait queues which contains 34 // linked list nodes. The kernel may write back to the non-node fields as well. 35 // TODO: add Unpin as a negative trait bound once the rustc feature is stabilized. 36 // impl !Unpin for event_t {} 37 38 #[derive(Debug)] 39 pub struct Event(Box<UnsafeCell<event_t>>); 40 41 impl Event { new(initial: bool, flags: uint) -> Self42 pub fn new(initial: bool, flags: uint) -> Self { 43 // SAFETY: event_t is a C type which can be zeroed out 44 let event = unsafe { mem::zeroed() }; 45 let mut boxed_event = Box::new(UnsafeCell::new(event)); 46 // SAFETY: event_init just writes to the fields of event_t. The self-referential `wait` 47 // field is written to after the event_t is placed on the heap so it won't become 48 // invalidated until it's dropped. 49 unsafe { event_init(boxed_event.get_mut(), initial, flags) }; 50 Self(boxed_event) 51 } 52 wait(&self) -> status_t53 pub fn wait(&self) -> status_t { 54 // SAFETY: One or more threads are allowed to wait for an event to be signaled 55 unsafe { event_wait_timeout(self.0.get(), INFINITE_TIME) } 56 } 57 signal(&self) -> status_t58 pub fn signal(&self) -> status_t { 59 // SAFETY: Events may be signaled from any thread or interrupt context if the reschedule 60 // parameter is false 61 unsafe { 62 event_signal(self.0.get(), false /* reschedule */) 63 } 64 } 65 } 66 67 // SAFETY: More than one thread may wait using an &Event but only one will be woken up and change 68 // its signaled field. &Event provides no other APIs to modify its state 69 unsafe impl Sync for Event {} 70 71 // SAFETY: Event is heap allocated so it may be freely sent across threads without invalidating it. 72 // It may also be waited on and signaled from any thread. 73 unsafe impl Send for Event {} 74