tokio/runtime/task/
abort.rs

1use crate::runtime::task::{Header, RawTask};
2use std::fmt;
3use std::panic::{RefUnwindSafe, UnwindSafe};
4
5/// An owned permission to abort a spawned task, without awaiting its completion.
6///
7/// Unlike a [`JoinHandle`], an `AbortHandle` does *not* represent the
8/// permission to await the task's completion, only to terminate it.
9///
10/// The task may be aborted by calling the [`AbortHandle::abort`] method.
11/// Dropping an `AbortHandle` releases the permission to terminate the task
12/// --- it does *not* abort the task.
13///
14/// Be aware that tasks spawned using [`spawn_blocking`] cannot be aborted
15/// because they are not async. If you call `abort` on a `spawn_blocking` task,
16/// then this *will not have any effect*, and the task will continue running
17/// normally. The exception is if the task has not started running yet; in that
18/// case, calling `abort` may prevent the task from starting.
19///
20/// [`JoinHandle`]: crate::task::JoinHandle
21/// [`spawn_blocking`]: crate::task::spawn_blocking
22#[cfg_attr(docsrs, doc(cfg(feature = "rt")))]
23pub struct AbortHandle {
24    raw: RawTask,
25}
26
27impl AbortHandle {
28    pub(super) fn new(raw: RawTask) -> Self {
29        Self { raw }
30    }
31
32    /// Abort the task associated with the handle.
33    ///
34    /// Awaiting a cancelled task might complete as usual if the task was
35    /// already completed at the time it was cancelled, but most likely it
36    /// will fail with a [cancelled] `JoinError`.
37    ///
38    /// If the task was already cancelled, such as by [`JoinHandle::abort`],
39    /// this method will do nothing.
40    ///
41    /// Be aware that tasks spawned using [`spawn_blocking`] cannot be aborted
42    /// because they are not async. If you call `abort` on a `spawn_blocking`
43    /// task, then this *will not have any effect*, and the task will continue
44    /// running normally. The exception is if the task has not started running
45    /// yet; in that case, calling `abort` may prevent the task from starting.
46    ///
47    /// See also [the module level docs] for more information on cancellation.
48    ///
49    /// [cancelled]: method@super::error::JoinError::is_cancelled
50    /// [`JoinHandle::abort`]: method@super::JoinHandle::abort
51    /// [the module level docs]: crate::task#cancellation
52    /// [`spawn_blocking`]: crate::task::spawn_blocking
53    pub fn abort(&self) {
54        self.raw.remote_abort();
55    }
56
57    /// Checks if the task associated with this `AbortHandle` has finished.
58    ///
59    /// Please note that this method can return `false` even if `abort` has been
60    /// called on the task. This is because the cancellation process may take
61    /// some time, and this method does not return `true` until it has
62    /// completed.
63    pub fn is_finished(&self) -> bool {
64        let state = self.raw.state().load();
65        state.is_complete()
66    }
67
68    /// Returns a [task ID] that uniquely identifies this task relative to other
69    /// currently spawned tasks.
70    ///
71    /// [task ID]: crate::task::Id
72    pub fn id(&self) -> super::Id {
73        // Safety: The header pointer is valid.
74        unsafe { Header::get_id(self.raw.header_ptr()) }
75    }
76}
77
78unsafe impl Send for AbortHandle {}
79unsafe impl Sync for AbortHandle {}
80
81impl UnwindSafe for AbortHandle {}
82impl RefUnwindSafe for AbortHandle {}
83
84impl fmt::Debug for AbortHandle {
85    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
86        // Safety: The header pointer is valid.
87        let id_ptr = unsafe { Header::get_id_ptr(self.raw.header_ptr()) };
88        let id = unsafe { id_ptr.as_ref() };
89        fmt.debug_struct("AbortHandle").field("id", id).finish()
90    }
91}
92
93impl Drop for AbortHandle {
94    fn drop(&mut self) {
95        self.raw.drop_abort_handle();
96    }
97}
98
99impl Clone for AbortHandle {
100    /// Returns a cloned `AbortHandle` that can be used to remotely abort this task.
101    fn clone(&self) -> Self {
102        self.raw.ref_inc();
103        Self::new(self.raw)
104    }
105}
tokio/runtime/task/abort.rs

tokio/runtime/task/
abort.rs
