      1
      2
      3
      4
      5
      6
      7
      8
      9
     10
     11
     12
     13
     14
     15
     16
     17
     18
     19
     20
     21
     22
     23
     24
     25
     26
     27
     28
     29
     30
     31
     32
     33
     34
     35
     36
     37
     38
     39
     40
     41
     42
     43
     44
     45
     46
     47
     48
     49
     50
     51
     52
     53
     54
     55
     56
     57
     58
     59
     60
     61
     62
     63
     64
     65
     66
     67
     68
     69
     70
     71
     72
     73
     74
     75
     76
     77
     78
     79
     80
     81
     82
     83
     84
     85
     86
     87
     88
     89
     90
     91
     92
     93
     94
     95
     96
     97
     98
     99
    100
    101
    102
    103
    104
    105
    106
    107
    108
    109
    110
    111
    112
    113
    114
    115
    116
    117
    118
    119
    120
    121
    122
    123
    124
    125
    126
    127
    128
    129
    130
    131
    132
    133
    134
    135
    136
    137
    138
    139
    140
    141
    142
    143
    144
    145
    146
    147
    148
    149
    150
    151
    152
    153
    154
    155
    156
    157
    158
    159
    160
    161
    162
    163
    164
    165
    166
    167
    168
    169
    170
    171
    172
    173
    174
    175
    176
    177
    178
    179
    180
    181
    182
    183
    184
    185
    186
    187
    188
    189
    190
    191
    192
    193
    194
    195
    196
    197
    198
    199
    200
    201
    202
    203
    204
    205
    206
    207
    208
    209
    210
    211
    212
    213
    214
    215
    216
    217
    218
    219
    220
    221
    222
    223
    224
    225
    226
    227
    228
    229
    230
    231
    232
    233
    234
    235
    236
    237
    238
    239
    240
    241
    242
    243
    244
    245
    246
    247
    248
    249
    250
    251
    252
    253
    254
    255
    256
    257
    258
    259
    260
    261
    262
    263
    264
    265
    266
    267
    268
    269
    270
    271
    272
    273
    274
    275
    276
    277
    278
    279
    280
    281
    282
    283
    284
    285
    286
    287
    288
    289
    290
    291
    292
    293
    294
    295
    296
    297
    298
    299
    300
    301
    302
    303
    304
    305
    306
    307
    308
    309

    use crate::process::imp::orphan::{OrphanQueue, Wait};
    use crate::process::kill::Kill;
    use crate::signal::unix::InternalStream;

    use std::future::Future;
    use std::io;
    use std::ops::Deref;
    use std::pin::Pin;
    use std::process::ExitStatus;
    use std::task::Context;
    use std::task::Poll;

    /// Orchestrates between registering interest for receiving signals when a
    /// child process has exited, and attempting to poll for process completion.
    #[derive(Debug)]
    pub(crate) struct Reaper<W, Q, S>
    where
        W: Wait + Unpin,
        Q: OrphanQueue<W>,
    {
        inner: Option<W>,
        orphan_queue: Q,
        signal: S,
    }

    impl<W, Q, S> Deref for Reaper<W, Q, S>
    where
        W: Wait + Unpin,
        Q: OrphanQueue<W>,
    {
        type Target = W;

        fn deref(&self) -> &Self::Target {
            self.inner()
        }
    }

    impl<W, Q, S> Reaper<W, Q, S>
    where
        W: Wait + Unpin,
        Q: OrphanQueue<W>,
    {
        pub(crate) fn new(inner: W, orphan_queue: Q, signal: S) -> Self {
            Self {
                inner: Some(inner),
                orphan_queue,
                signal,
            }
        }

        fn inner(&self) -> &W {
            self.inner.as_ref().expect("inner has gone away")
        }

        pub(crate) fn inner_mut(&mut self) -> &mut W {
            self.inner.as_mut().expect("inner has gone away")
        }
    }

    impl<W, Q, S> Future for Reaper<W, Q, S>
    where
        W: Wait + Unpin,
        Q: OrphanQueue<W> + Unpin,
        S: InternalStream,
    {
        type Output = io::Result<ExitStatus>;

        fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
            loop {
                // If the child hasn't exited yet, then it's our responsibility to
                // ensure the current task gets notified when it might be able to
                // make progress. We can use the delivery of a SIGCHLD signal as a
                // sign that we can potentially make progress.
                //
                // However, we will register for a notification on the next signal
                // BEFORE we poll the child. Otherwise it is possible that the child
                // can exit and the signal can arrive after we last polled the child,
                // but before we've registered for a notification on the next signal
                // (this can cause a deadlock if there are no more spawned children
                // which can generate a different signal for us). A side effect of
                // pre-registering for signal notifications is that when the child
                // exits, we will have already registered for an additional
                // notification we don't need to consume. If another signal arrives,
                // this future's task will be notified/woken up again. Since the
                // futures model allows for spurious wake ups this extra wakeup
                // should not cause significant issues with parent futures.
                let registered_interest = self.signal.poll_recv(cx).is_pending();

                if let Some(status) = self.inner_mut().try_wait()? {
                    return Poll::Ready(Ok(status));
                }

                // If our attempt to poll for the next signal was not ready, then
                // we've arranged for our task to get notified and we can bail out.
                if registered_interest {
                    return Poll::Pending;
                } else {
                    // Otherwise, if the signal stream delivered a signal to us, we
                    // won't get notified at the next signal, so we'll loop and try
                    // again.
                    continue;
                }
            }
        }
    }

    impl<W, Q, S> Kill for Reaper<W, Q, S>
    where
        W: Kill + Wait + Unpin,
        Q: OrphanQueue<W>,
    {
        fn kill(&mut self) -> io::Result<()> {
            self.inner_mut().kill()
        }
    }

    impl<W, Q, S> Drop for Reaper<W, Q, S>
    where
        W: Wait + Unpin,
        Q: OrphanQueue<W>,
    {
        fn drop(&mut self) {
            if let Ok(Some(_)) = self.inner_mut().try_wait() {
                return;
            }

            let orphan = self.inner.take().unwrap();
            self.orphan_queue.push_orphan(orphan);
        }
    }

    #[cfg(all(test, not(loom)))]
    mod test {
        use super::*;

        use crate::process::unix::orphan::test::MockQueue;
        use crate::sync::mpsc::error::TryRecvError;
        use futures::future::FutureExt;
        use std::os::unix::process::ExitStatusExt;
        use std::process::ExitStatus;
        use std::task::Context;
        use std::task::Poll;

        #[derive(Debug)]
        struct MockWait {
            total_kills: usize,
            total_waits: usize,
            num_wait_until_status: usize,
            status: ExitStatus,
        }

        impl MockWait {
            fn new(status: ExitStatus, num_wait_until_status: usize) -> Self {
                Self {
                    total_kills: 0,
                    total_waits: 0,
                    num_wait_until_status,
                    status,
                }
            }
        }

        impl Wait for MockWait {
            fn id(&self) -> u32 {
                0
            }

            fn try_wait(&mut self) -> io::Result<Option<ExitStatus>> {
                let ret = if self.num_wait_until_status == self.total_waits {
                    Some(self.status)
                } else {
                    None
                };

                self.total_waits += 1;
                Ok(ret)
            }
        }

        impl Kill for MockWait {
            fn kill(&mut self) -> io::Result<()> {
                self.total_kills += 1;
                Ok(())
            }
        }

        struct MockStream {
            total_polls: usize,
            values: Vec<Option<()>>,
        }

        impl MockStream {
            fn new(values: Vec<Option<()>>) -> Self {
                Self {
                    total_polls: 0,
                    values,
                }
            }
        }

        impl InternalStream for MockStream {
            fn poll_recv(&mut self, _cx: &mut Context<'_>) -> Poll<Option<()>> {
                self.total_polls += 1;
                match self.values.remove(0) {
                    Some(()) => Poll::Ready(Some(())),
                    None => Poll::Pending,
                }
            }

            fn try_recv(&mut self) -> Result<(), TryRecvError> {
                unimplemented!();
            }
        }

        #[test]
        fn reaper() {
            let exit = ExitStatus::from_raw(0);
            let mock = MockWait::new(exit, 3);
            let mut grim = Reaper::new(
                mock,
                MockQueue::new(),
                MockStream::new(vec![None, Some(()), None, None, None]),
            );

            let waker = futures::task::noop_waker();
            let mut context = Context::from_waker(&waker);

            // Not yet exited, interest registered
            assert!(grim.poll_unpin(&mut context).is_pending());
            assert_eq!(1, grim.signal.total_polls);
            assert_eq!(1, grim.total_waits);
            assert_eq!(0, grim.orphan_queue.total_reaps.get());
            assert!(grim.orphan_queue.all_enqueued.borrow().is_empty());

            // Not yet exited, couldn't register interest the first time
            // but managed to register interest the second time around
            assert!(grim.poll_unpin(&mut context).is_pending());
            assert_eq!(3, grim.signal.total_polls);
            assert_eq!(3, grim.total_waits);
            assert_eq!(0, grim.orphan_queue.total_reaps.get());
            assert!(grim.orphan_queue.all_enqueued.borrow().is_empty());

            // Exited
            if let Poll::Ready(r) = grim.poll_unpin(&mut context) {
                assert!(r.is_ok());
                let exit_code = r.unwrap();
                assert_eq!(exit_code, exit);
            } else {
                unreachable!();
            }
            assert_eq!(4, grim.signal.total_polls);
            assert_eq!(4, grim.total_waits);
            assert_eq!(0, grim.orphan_queue.total_reaps.get());
            assert!(grim.orphan_queue.all_enqueued.borrow().is_empty());
        }

        #[test]
        fn kill() {
            let exit = ExitStatus::from_raw(0);
            let mut grim = Reaper::new(
                MockWait::new(exit, 0),
                MockQueue::new(),
                MockStream::new(vec![None]),
            );

            grim.kill().unwrap();
            assert_eq!(1, grim.total_kills);
            assert_eq!(0, grim.orphan_queue.total_reaps.get());
            assert!(grim.orphan_queue.all_enqueued.borrow().is_empty());
        }

        #[test]
        fn drop_reaps_if_possible() {
            let exit = ExitStatus::from_raw(0);
            let mut mock = MockWait::new(exit, 0);

            {
                let queue = MockQueue::new();

                let grim = Reaper::new(&mut mock, &queue, MockStream::new(vec![]));

                drop(grim);

                assert_eq!(0, queue.total_reaps.get());
                assert!(queue.all_enqueued.borrow().is_empty());
            }

            assert_eq!(1, mock.total_waits);
            assert_eq!(0, mock.total_kills);
        }

        #[test]
        fn drop_enqueues_orphan_if_wait_fails() {
            let exit = ExitStatus::from_raw(0);
            let mut mock = MockWait::new(exit, 2);

            {
                let queue = MockQueue::<&mut MockWait>::new();
                let grim = Reaper::new(&mut mock, &queue, MockStream::new(vec![]));
                drop(grim);

                assert_eq!(0, queue.total_reaps.get());
                assert_eq!(1, queue.all_enqueued.borrow().len());
            }

            assert_eq!(1, mock.total_waits);
            assert_eq!(0, mock.total_kills);
        }
    }