      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

    use error::{Error};
    use fmt;
    use sync::atomic::{AtomicBool, Ordering};
    use thread;

    pub struct Flag { failed: AtomicBool }

    // Note that the Ordering uses to access the `failed` field of `Flag` below is
    // always `Relaxed`, and that's because this isn't actually protecting any data,
    // it's just a flag whether we've panicked or not.
    //
    // The actual location that this matters is when a mutex is **locked** which is
    // where we have external synchronization ensuring that we see memory
    // reads/writes to this flag.
    //
    // As a result, if it matters, we should see the correct value for `failed` in
    // all cases.

    impl Flag {
        pub const fn new() -> Flag {
            Flag { failed: AtomicBool::new(false) }
        }

        #[inline]
        pub fn borrow(&self) -> LockResult<Guard> {
            let ret = Guard { panicking: thread::panicking() };
            if self.get() {
                Err(PoisonError::new(ret))
            } else {
                Ok(ret)
            }
        }

        #[inline]
        pub fn done(&self, guard: &Guard) {
            if !guard.panicking && thread::panicking() {
                self.failed.store(true, Ordering::Relaxed);
            }
        }

        #[inline]
        pub fn get(&self) -> bool {
            self.failed.load(Ordering::Relaxed)
        }
    }

    pub struct Guard {
        panicking: bool,
    }

    /// A type of error which can be returned whenever a lock is acquired.
    ///
    /// Both [`Mutex`]es and [`RwLock`]s are poisoned whenever a thread fails while the lock
    /// is held. The precise semantics for when a lock is poisoned is documented on
    /// each lock, but once a lock is poisoned then all future acquisitions will
    /// return this error.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::sync::{Arc, Mutex};
    /// use std::thread;
    ///
    /// let mutex = Arc::new(Mutex::new(1));
    ///
    /// // poison the mutex
    /// let c_mutex = mutex.clone();
    /// let _ = thread::spawn(move || {
    ///     let mut data = c_mutex.lock().unwrap();
    ///     *data = 2;
    ///     panic!();
    /// }).join();
    ///
    /// match mutex.lock() {
    ///     Ok(_) => unreachable!(),
    ///     Err(p_err) => {
    ///         let data = p_err.get_ref();
    ///         println!("recovered: {}", data);
    ///     }
    /// };
    /// ```
    ///
    /// [`Mutex`]: ../../std/sync/struct.Mutex.html
    /// [`RwLock`]: ../../std/sync/struct.RwLock.html
    #[stable(feature = "rust1", since = "1.0.0")]
    pub struct PoisonError<T> {
        guard: T,
    }

    /// An enumeration of possible errors associated with a [`TryLockResult`] which
    /// can occur while trying to acquire a lock, from the [`try_lock`] method on a
    /// [`Mutex`] or the [`try_read`] and [`try_write`] methods on an [`RwLock`].
    ///
    /// [`Mutex`]: struct.Mutex.html
    /// [`RwLock`]: struct.RwLock.html
    /// [`TryLockResult`]: type.TryLockResult.html
    /// [`try_lock`]: struct.Mutex.html#method.try_lock
    /// [`try_read`]: struct.RwLock.html#method.try_read
    /// [`try_write`]: struct.RwLock.html#method.try_write
    #[stable(feature = "rust1", since = "1.0.0")]
    pub enum TryLockError<T> {
        /// The lock could not be acquired because another thread failed while holding
        /// the lock.
        #[stable(feature = "rust1", since = "1.0.0")]
        Poisoned(#[stable(feature = "rust1", since = "1.0.0")] PoisonError<T>),
        /// The lock could not be acquired at this time because the operation would
        /// otherwise block.
        #[stable(feature = "rust1", since = "1.0.0")]
        WouldBlock,
    }

    /// A type alias for the result of a lock method which can be poisoned.
    ///
    /// The [`Ok`] variant of this result indicates that the primitive was not
    /// poisoned, and the `Guard` is contained within. The [`Err`] variant indicates
    /// that the primitive was poisoned. Note that the [`Err`] variant *also* carries
    /// the associated guard, and it can be acquired through the [`into_inner`]
    /// method.
    ///
    /// [`Ok`]: ../../std/result/enum.Result.html#variant.Ok
    /// [`Err`]: ../../std/result/enum.Result.html#variant.Err
    /// [`into_inner`]: ../../std/sync/struct.PoisonError.html#method.into_inner
    #[stable(feature = "rust1", since = "1.0.0")]
    pub type LockResult<Guard> = Result<Guard, PoisonError<Guard>>;

    /// A type alias for the result of a nonblocking locking method.
    ///
    /// For more information, see [`LockResult`]. A `TryLockResult` doesn't
    /// necessarily hold the associated guard in the [`Err`] type as the lock may not
    /// have been acquired for other reasons.
    ///
    /// [`LockResult`]: ../../std/sync/type.LockResult.html
    /// [`Err`]: ../../std/result/enum.Result.html#variant.Err
    #[stable(feature = "rust1", since = "1.0.0")]
    pub type TryLockResult<Guard> = Result<Guard, TryLockError<Guard>>;

    #[stable(feature = "rust1", since = "1.0.0")]
    impl<T> fmt::Debug for PoisonError<T> {
        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
            "PoisonError { inner: .. }".fmt(f)
        }
    }

    #[stable(feature = "rust1", since = "1.0.0")]
    impl<T> fmt::Display for PoisonError<T> {
        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
            "poisoned lock: another task failed inside".fmt(f)
        }
    }

    #[stable(feature = "rust1", since = "1.0.0")]
    impl<T> Error for PoisonError<T> {
        fn description(&self) -> &str {
            "poisoned lock: another task failed inside"
        }
    }

    impl<T> PoisonError<T> {
        /// Creates a `PoisonError`.
        ///
        /// This is generally created by methods like [`Mutex::lock`] or [`RwLock::read`].
        ///
        /// [`Mutex::lock`]: ../../std/sync/struct.Mutex.html#method.lock
        /// [`RwLock::read`]: ../../std/sync/struct.RwLock.html#method.read
        #[stable(feature = "sync_poison", since = "1.2.0")]
        pub fn new(guard: T) -> PoisonError<T> {
            PoisonError { guard }
        }

        /// Consumes this error indicating that a lock is poisoned, returning the
        /// underlying guard to allow access regardless.
        ///
        /// # Examples
        ///
        /// ```
        /// use std::collections::HashSet;
        /// use std::sync::{Arc, Mutex};
        /// use std::thread;
        ///
        /// let mutex = Arc::new(Mutex::new(HashSet::new()));
        ///
        /// // poison the mutex
        /// let c_mutex = mutex.clone();
        /// let _ = thread::spawn(move || {
        ///     let mut data = c_mutex.lock().unwrap();
        ///     data.insert(10);
        ///     panic!();
        /// }).join();
        ///
        /// let p_err = mutex.lock().unwrap_err();
        /// let data = p_err.into_inner();
        /// println!("recovered {} items", data.len());
        /// ```
        #[stable(feature = "sync_poison", since = "1.2.0")]
        pub fn into_inner(self) -> T { self.guard }

        /// Reaches into this error indicating that a lock is poisoned, returning a
        /// reference to the underlying guard to allow access regardless.
        #[stable(feature = "sync_poison", since = "1.2.0")]
        pub fn get_ref(&self) -> &T { &self.guard }

        /// Reaches into this error indicating that a lock is poisoned, returning a
        /// mutable reference to the underlying guard to allow access regardless.
        #[stable(feature = "sync_poison", since = "1.2.0")]
        pub fn get_mut(&mut self) -> &mut T { &mut self.guard }
    }

    #[stable(feature = "rust1", since = "1.0.0")]
    impl<T> From<PoisonError<T>> for TryLockError<T> {
        fn from(err: PoisonError<T>) -> TryLockError<T> {
            TryLockError::Poisoned(err)
        }
    }

    #[stable(feature = "rust1", since = "1.0.0")]
    impl<T> fmt::Debug for TryLockError<T> {
        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
            match *self {
                TryLockError::Poisoned(..) => "Poisoned(..)".fmt(f),
                TryLockError::WouldBlock => "WouldBlock".fmt(f)
            }
        }
    }

    #[stable(feature = "rust1", since = "1.0.0")]
    impl<T> fmt::Display for TryLockError<T> {
        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
            match *self {
                TryLockError::Poisoned(..) => "poisoned lock: another task failed inside",
                TryLockError::WouldBlock => "try_lock failed because the operation would block"
            }.fmt(f)
        }
    }

    #[stable(feature = "rust1", since = "1.0.0")]
    impl<T> Error for TryLockError<T> {
        fn description(&self) -> &str {
            match *self {
                TryLockError::Poisoned(ref p) => p.description(),
                TryLockError::WouldBlock => "try_lock failed because the operation would block"
            }
        }

        fn cause(&self) -> Option<&dyn Error> {
            match *self {
                TryLockError::Poisoned(ref p) => Some(p),
                _ => None
            }
        }
    }

    pub fn map_result<T, U, F>(result: LockResult<T>, f: F)
                               -> LockResult<U>
                               where F: FnOnce(T) -> U {
        match result {
            Ok(t) => Ok(f(t)),
            Err(PoisonError { guard }) => Err(PoisonError::new(f(guard)))
        }
    }

# Help

## Keyboard Shortcuts

`?`
  Show this help dialog
`S`
  Focus the search field
`↑`
  Move up in search results
`↓`
  Move down in search results
`↹`
  Switch tab
`⏎`
  Go to active search result
`+`
  Expand all sections
`-`
  Collapse all sections

## Search Tricks

Prefix searches with a type followed by a colon (e.g., `fn:`) to restrict the search to a given type.

Accepted types are: `fn`, `mod`, `struct`, `enum`, `trait`, `type`, `macro`, and `const`.

Search functions by type signature (e.g., `vec -> usize` or `* -> vec`)

Search multiple things at once by splitting your query with comma (e.g., `str,u8` or `String,struct:Vec,test`)