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Commit | Line | Data |
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1a4d82fc | 1 | //! Thread local storage |
c34b1796 | 2 | |
e9174d1e | 3 | #![unstable(feature = "thread_local_internals", issue = "0")] |
1a4d82fc | 4 | |
532ac7d7 | 5 | use crate::fmt; |
1a4d82fc JJ |
6 | |
7 | /// A thread local storage key which owns its contents. | |
8 | /// | |
9 | /// This key uses the fastest possible implementation available to it for the | |
7cac9316 XL |
10 | /// target platform. It is instantiated with the [`thread_local!`] macro and the |
11 | /// primary method is the [`with`] method. | |
1a4d82fc | 12 | /// |
7cac9316 | 13 | /// The [`with`] method yields a reference to the contained value which cannot be |
bd371182 | 14 | /// sent across threads or escape the given closure. |
1a4d82fc JJ |
15 | /// |
16 | /// # Initialization and Destruction | |
17 | /// | |
7cac9316 XL |
18 | /// Initialization is dynamically performed on the first call to [`with`] |
19 | /// within a thread, and values that implement [`Drop`] get destructed when a | |
8bb4bdeb | 20 | /// thread exits. Some caveats apply, which are explained below. |
1a4d82fc | 21 | /// |
ea8adc8c XL |
22 | /// A `LocalKey`'s initializer cannot recursively depend on itself, and using |
23 | /// a `LocalKey` in this way will cause the initializer to infinitely recurse | |
24 | /// on the first call to `with`. | |
25 | /// | |
c34b1796 | 26 | /// # Examples |
1a4d82fc JJ |
27 | /// |
28 | /// ``` | |
29 | /// use std::cell::RefCell; | |
85aaf69f | 30 | /// use std::thread; |
1a4d82fc | 31 | /// |
c34b1796 | 32 | /// thread_local!(static FOO: RefCell<u32> = RefCell::new(1)); |
1a4d82fc JJ |
33 | /// |
34 | /// FOO.with(|f| { | |
35 | /// assert_eq!(*f.borrow(), 1); | |
36 | /// *f.borrow_mut() = 2; | |
37 | /// }); | |
38 | /// | |
39 | /// // each thread starts out with the initial value of 1 | |
532ac7d7 | 40 | /// let t = thread::spawn(move|| { |
1a4d82fc JJ |
41 | /// FOO.with(|f| { |
42 | /// assert_eq!(*f.borrow(), 1); | |
43 | /// *f.borrow_mut() = 3; | |
44 | /// }); | |
45 | /// }); | |
46 | /// | |
532ac7d7 XL |
47 | /// // wait for the thread to complete and bail out on panic |
48 | /// t.join().unwrap(); | |
49 | /// | |
1a4d82fc JJ |
50 | /// // we retain our original value of 2 despite the child thread |
51 | /// FOO.with(|f| { | |
52 | /// assert_eq!(*f.borrow(), 2); | |
53 | /// }); | |
54 | /// ``` | |
7453a54e SL |
55 | /// |
56 | /// # Platform-specific behavior | |
57 | /// | |
58 | /// Note that a "best effort" is made to ensure that destructors for types | |
a7813a04 | 59 | /// stored in thread local storage are run, but not all platforms can guarantee |
7453a54e SL |
60 | /// that destructors will be run for all types in thread local storage. For |
61 | /// example, there are a number of known caveats where destructors are not run: | |
62 | /// | |
63 | /// 1. On Unix systems when pthread-based TLS is being used, destructors will | |
64 | /// not be run for TLS values on the main thread when it exits. Note that the | |
65 | /// application will exit immediately after the main thread exits as well. | |
66 | /// 2. On all platforms it's possible for TLS to re-initialize other TLS slots | |
67 | /// during destruction. Some platforms ensure that this cannot happen | |
68 | /// infinitely by preventing re-initialization of any slot that has been | |
69 | /// destroyed, but not all platforms have this guard. Those platforms that do | |
70 | /// not guard typically have a synthetic limit after which point no more | |
71 | /// destructors are run. | |
7cac9316 XL |
72 | /// |
73 | /// [`with`]: ../../std/thread/struct.LocalKey.html#method.with | |
74 | /// [`thread_local!`]: ../../std/macro.thread_local.html | |
75 | /// [`Drop`]: ../../std/ops/trait.Drop.html | |
85aaf69f | 76 | #[stable(feature = "rust1", since = "1.0.0")] |
9cc50fc6 SL |
77 | pub struct LocalKey<T: 'static> { |
78 | // This outer `LocalKey<T>` type is what's going to be stored in statics, | |
79 | // but actual data inside will sometimes be tagged with #[thread_local]. | |
80 | // It's not valid for a true static to reference a #[thread_local] static, | |
81 | // so we get around that by exposing an accessor through a layer of function | |
82 | // indirection (this thunk). | |
1a4d82fc | 83 | // |
9cc50fc6 SL |
84 | // Note that the thunk is itself unsafe because the returned lifetime of the |
85 | // slot where data lives, `'static`, is not actually valid. The lifetime | |
3b2f2976 | 86 | // here is actually slightly shorter than the currently running thread! |
9cc50fc6 SL |
87 | // |
88 | // Although this is an extra layer of indirection, it should in theory be | |
89 | // trivially devirtualizable by LLVM because the value of `inner` never | |
90 | // changes and the constant should be readonly within a crate. This mainly | |
91 | // only runs into problems when TLS statics are exported across crates. | |
dc9dc135 | 92 | inner: unsafe fn() -> Option<&'static T>, |
1a4d82fc JJ |
93 | } |
94 | ||
8bb4bdeb | 95 | #[stable(feature = "std_debug", since = "1.16.0")] |
32a655c1 | 96 | impl<T: 'static> fmt::Debug for LocalKey<T> { |
532ac7d7 | 97 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
32a655c1 SL |
98 | f.pad("LocalKey { .. }") |
99 | } | |
100 | } | |
101 | ||
7cac9316 | 102 | /// Declare a new thread local storage key of type [`std::thread::LocalKey`]. |
62682a34 | 103 | /// |
3157f602 XL |
104 | /// # Syntax |
105 | /// | |
106 | /// The macro wraps any number of static declarations and makes them thread local. | |
041b39d2 | 107 | /// Publicity and attributes for each static are allowed. Example: |
3157f602 XL |
108 | /// |
109 | /// ``` | |
110 | /// use std::cell::RefCell; | |
111 | /// thread_local! { | |
112 | /// pub static FOO: RefCell<u32> = RefCell::new(1); | |
113 | /// | |
114 | /// #[allow(unused)] | |
115 | /// static BAR: RefCell<f32> = RefCell::new(1.0); | |
116 | /// } | |
117 | /// # fn main() {} | |
118 | /// ``` | |
119 | /// | |
7cac9316 | 120 | /// See [LocalKey documentation][`std::thread::LocalKey`] for more |
62682a34 | 121 | /// information. |
7cac9316 XL |
122 | /// |
123 | /// [`std::thread::LocalKey`]: ../std/thread/struct.LocalKey.html | |
1a4d82fc | 124 | #[macro_export] |
62682a34 | 125 | #[stable(feature = "rust1", since = "1.0.0")] |
532ac7d7 | 126 | #[allow_internal_unstable(thread_local_internals)] |
041b39d2 XL |
127 | macro_rules! thread_local { |
128 | // empty (base case for the recursion) | |
129 | () => {}; | |
130 | ||
131 | // process multiple declarations | |
132 | ($(#[$attr:meta])* $vis:vis static $name:ident: $t:ty = $init:expr; $($rest:tt)*) => ( | |
a1dfa0c6 XL |
133 | $crate::__thread_local_inner!($(#[$attr])* $vis $name, $t, $init); |
134 | $crate::thread_local!($($rest)*); | |
041b39d2 XL |
135 | ); |
136 | ||
137 | // handle a single declaration | |
138 | ($(#[$attr:meta])* $vis:vis static $name:ident: $t:ty = $init:expr) => ( | |
a1dfa0c6 | 139 | $crate::__thread_local_inner!($(#[$attr])* $vis $name, $t, $init); |
041b39d2 XL |
140 | ); |
141 | } | |
142 | ||
041b39d2 XL |
143 | #[doc(hidden)] |
144 | #[unstable(feature = "thread_local_internals", | |
145 | reason = "should not be necessary", | |
146 | issue = "0")] | |
147 | #[macro_export] | |
532ac7d7 | 148 | #[allow_internal_unstable(thread_local_internals, cfg_target_thread_local, thread_local)] |
ea8adc8c | 149 | #[allow_internal_unsafe] |
041b39d2 | 150 | macro_rules! __thread_local_inner { |
ea8adc8c XL |
151 | (@key $(#[$attr:meta])* $vis:vis $name:ident, $t:ty, $init:expr) => { |
152 | { | |
153 | #[inline] | |
041b39d2 XL |
154 | fn __init() -> $t { $init } |
155 | ||
dc9dc135 | 156 | unsafe fn __getit() -> $crate::option::Option<&'static $t> { |
0bf4aa26 | 157 | #[cfg(all(target_arch = "wasm32", not(target_feature = "atomics")))] |
83c7162d XL |
158 | static __KEY: $crate::thread::__StaticLocalKeyInner<$t> = |
159 | $crate::thread::__StaticLocalKeyInner::new(); | |
160 | ||
041b39d2 | 161 | #[thread_local] |
0bf4aa26 XL |
162 | #[cfg(all( |
163 | target_thread_local, | |
164 | not(all(target_arch = "wasm32", not(target_feature = "atomics"))), | |
165 | ))] | |
041b39d2 XL |
166 | static __KEY: $crate::thread::__FastLocalKeyInner<$t> = |
167 | $crate::thread::__FastLocalKeyInner::new(); | |
168 | ||
0bf4aa26 XL |
169 | #[cfg(all( |
170 | not(target_thread_local), | |
171 | not(all(target_arch = "wasm32", not(target_feature = "atomics"))), | |
172 | ))] | |
041b39d2 XL |
173 | static __KEY: $crate::thread::__OsLocalKeyInner<$t> = |
174 | $crate::thread::__OsLocalKeyInner::new(); | |
175 | ||
dc9dc135 | 176 | __KEY.get(__init) |
041b39d2 XL |
177 | } |
178 | ||
3b2f2976 | 179 | unsafe { |
dc9dc135 | 180 | $crate::thread::LocalKey::new(__getit) |
3b2f2976 | 181 | } |
ea8adc8c XL |
182 | } |
183 | }; | |
184 | ($(#[$attr:meta])* $vis:vis $name:ident, $t:ty, $init:expr) => { | |
ea8adc8c | 185 | $(#[$attr])* $vis const $name: $crate::thread::LocalKey<$t> = |
a1dfa0c6 | 186 | $crate::__thread_local_inner!(@key $(#[$attr])* $vis $name, $t, $init); |
041b39d2 XL |
187 | } |
188 | } | |
189 | ||
041b39d2 | 190 | /// An error returned by [`LocalKey::try_with`](struct.LocalKey.html#method.try_with). |
0531ce1d | 191 | #[stable(feature = "thread_local_try_with", since = "1.26.0")] |
041b39d2 XL |
192 | pub struct AccessError { |
193 | _private: (), | |
194 | } | |
195 | ||
0531ce1d | 196 | #[stable(feature = "thread_local_try_with", since = "1.26.0")] |
041b39d2 | 197 | impl fmt::Debug for AccessError { |
532ac7d7 | 198 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
041b39d2 XL |
199 | f.debug_struct("AccessError").finish() |
200 | } | |
201 | } | |
202 | ||
0531ce1d | 203 | #[stable(feature = "thread_local_try_with", since = "1.26.0")] |
041b39d2 | 204 | impl fmt::Display for AccessError { |
532ac7d7 | 205 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
041b39d2 XL |
206 | fmt::Display::fmt("already destroyed", f) |
207 | } | |
208 | } | |
209 | ||
c34b1796 | 210 | impl<T: 'static> LocalKey<T> { |
62682a34 SL |
211 | #[doc(hidden)] |
212 | #[unstable(feature = "thread_local_internals", | |
e9174d1e SL |
213 | reason = "recently added to create a key", |
214 | issue = "0")] | |
dc9dc135 | 215 | pub const unsafe fn new(inner: unsafe fn() -> Option<&'static T>) -> LocalKey<T> { |
62682a34 | 216 | LocalKey { |
3b2f2976 | 217 | inner, |
62682a34 SL |
218 | } |
219 | } | |
220 | ||
9346a6ac | 221 | /// Acquires a reference to the value in this TLS key. |
1a4d82fc JJ |
222 | /// |
223 | /// This will lazily initialize the value if this thread has not referenced | |
224 | /// this key yet. | |
225 | /// | |
226 | /// # Panics | |
227 | /// | |
228 | /// This function will `panic!()` if the key currently has its | |
229 | /// destructor running, and it **may** panic if the destructor has | |
230 | /// previously been run for this thread. | |
85aaf69f | 231 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc JJ |
232 | pub fn with<F, R>(&'static self, f: F) -> R |
233 | where F: FnOnce(&T) -> R { | |
041b39d2 XL |
234 | self.try_with(f).expect("cannot access a TLS value during or \ |
235 | after it is destroyed") | |
1a4d82fc JJ |
236 | } |
237 | ||
041b39d2 XL |
238 | /// Acquires a reference to the value in this TLS key. |
239 | /// | |
240 | /// This will lazily initialize the value if this thread has not referenced | |
241 | /// this key yet. If the key has been destroyed (which may happen if this is called | |
8faf50e0 | 242 | /// in a destructor), this function will return an [`AccessError`](struct.AccessError.html). |
041b39d2 XL |
243 | /// |
244 | /// # Panics | |
245 | /// | |
246 | /// This function will still `panic!()` if the key is uninitialized and the | |
247 | /// key's initializer panics. | |
0531ce1d | 248 | #[stable(feature = "thread_local_try_with", since = "1.26.0")] |
041b39d2 | 249 | pub fn try_with<F, R>(&'static self, f: F) -> Result<R, AccessError> |
0531ce1d XL |
250 | where |
251 | F: FnOnce(&T) -> R, | |
252 | { | |
041b39d2 | 253 | unsafe { |
dc9dc135 | 254 | let thread_local = (self.inner)().ok_or(AccessError { |
041b39d2 XL |
255 | _private: (), |
256 | })?; | |
dc9dc135 XL |
257 | Ok(f(thread_local)) |
258 | } | |
259 | } | |
260 | } | |
261 | ||
262 | mod lazy { | |
263 | use crate::cell::UnsafeCell; | |
264 | use crate::mem; | |
265 | use crate::hint; | |
266 | ||
267 | pub struct LazyKeyInner<T> { | |
268 | inner: UnsafeCell<Option<T>>, | |
269 | } | |
270 | ||
271 | impl<T> LazyKeyInner<T> { | |
272 | pub const fn new() -> LazyKeyInner<T> { | |
273 | LazyKeyInner { | |
274 | inner: UnsafeCell::new(None), | |
275 | } | |
276 | } | |
277 | ||
278 | pub unsafe fn get(&self) -> Option<&'static T> { | |
279 | (*self.inner.get()).as_ref() | |
280 | } | |
281 | ||
282 | pub unsafe fn initialize<F: FnOnce() -> T>(&self, init: F) -> &'static T { | |
283 | // Execute the initialization up front, *then* move it into our slot, | |
284 | // just in case initialization fails. | |
285 | let value = init(); | |
286 | let ptr = self.inner.get(); | |
287 | ||
288 | // note that this can in theory just be `*ptr = Some(value)`, but due to | |
289 | // the compiler will currently codegen that pattern with something like: | |
290 | // | |
291 | // ptr::drop_in_place(ptr) | |
292 | // ptr::write(ptr, Some(value)) | |
293 | // | |
294 | // Due to this pattern it's possible for the destructor of the value in | |
295 | // `ptr` (e.g., if this is being recursively initialized) to re-access | |
296 | // TLS, in which case there will be a `&` and `&mut` pointer to the same | |
297 | // value (an aliasing violation). To avoid setting the "I'm running a | |
298 | // destructor" flag we just use `mem::replace` which should sequence the | |
299 | // operations a little differently and make this safe to call. | |
300 | mem::replace(&mut *ptr, Some(value)); | |
301 | ||
302 | // After storing `Some` we want to get a reference to the contents of | |
303 | // what we just stored. While we could use `unwrap` here and it should | |
304 | // always work it empirically doesn't seem to always get optimized away, | |
305 | // which means that using something like `try_with` can pull in | |
306 | // panicking code and cause a large size bloat. | |
307 | match *ptr { | |
308 | Some(ref x) => x, | |
309 | None => hint::unreachable_unchecked(), | |
310 | } | |
311 | } | |
312 | ||
313 | #[allow(unused)] | |
314 | pub unsafe fn take(&mut self) -> Option<T> { | |
315 | (*self.inner.get()).take() | |
041b39d2 XL |
316 | } |
317 | } | |
318 | } | |
319 | ||
83c7162d XL |
320 | /// On some platforms like wasm32 there's no threads, so no need to generate |
321 | /// thread locals and we can instead just use plain statics! | |
322 | #[doc(hidden)] | |
0bf4aa26 | 323 | #[cfg(all(target_arch = "wasm32", not(target_feature = "atomics")))] |
83c7162d | 324 | pub mod statik { |
dc9dc135 | 325 | use super::lazy::LazyKeyInner; |
532ac7d7 | 326 | use crate::fmt; |
83c7162d XL |
327 | |
328 | pub struct Key<T> { | |
dc9dc135 | 329 | inner: LazyKeyInner<T>, |
83c7162d XL |
330 | } |
331 | ||
532ac7d7 | 332 | unsafe impl<T> Sync for Key<T> { } |
83c7162d XL |
333 | |
334 | impl<T> fmt::Debug for Key<T> { | |
532ac7d7 | 335 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
83c7162d XL |
336 | f.pad("Key { .. }") |
337 | } | |
338 | } | |
339 | ||
340 | impl<T> Key<T> { | |
341 | pub const fn new() -> Key<T> { | |
342 | Key { | |
dc9dc135 | 343 | inner: LazyKeyInner::new(), |
83c7162d XL |
344 | } |
345 | } | |
346 | ||
dc9dc135 XL |
347 | pub unsafe fn get(&self, init: fn() -> T) -> Option<&'static T> { |
348 | let value = match self.inner.get() { | |
349 | Some(ref value) => value, | |
350 | None => self.inner.initialize(init), | |
351 | }; | |
352 | Some(value) | |
83c7162d XL |
353 | } |
354 | } | |
355 | } | |
356 | ||
041b39d2 XL |
357 | #[doc(hidden)] |
358 | #[cfg(target_thread_local)] | |
359 | pub mod fast { | |
dc9dc135 XL |
360 | use super::lazy::LazyKeyInner; |
361 | use crate::cell::Cell; | |
532ac7d7 XL |
362 | use crate::fmt; |
363 | use crate::mem; | |
dc9dc135 | 364 | use crate::sys::fast_thread_local::register_dtor; |
041b39d2 | 365 | |
dc9dc135 XL |
366 | #[derive(Copy, Clone)] |
367 | enum DtorState { | |
368 | Unregistered, | |
369 | Registered, | |
370 | RunningOrHasRun, | |
371 | } | |
372 | ||
373 | // This data structure has been carefully constructed so that the fast path | |
374 | // only contains one branch on x86. That optimization is necessary to avoid | |
375 | // duplicated tls lookups on OSX. | |
376 | // | |
377 | // LLVM issue: https://bugs.llvm.org/show_bug.cgi?id=41722 | |
041b39d2 | 378 | pub struct Key<T> { |
dc9dc135 XL |
379 | // If `LazyKeyInner::get` returns `None`, that indicates either: |
380 | // * The value has never been initialized | |
381 | // * The value is being recursively initialized | |
382 | // * The value has already been destroyed or is being destroyed | |
383 | // To determine which kind of `None`, check `dtor_state`. | |
384 | // | |
385 | // This is very optimizer friendly for the fast path - initialized but | |
386 | // not yet dropped. | |
387 | inner: LazyKeyInner<T>, | |
041b39d2 XL |
388 | |
389 | // Metadata to keep track of the state of the destructor. Remember that | |
dc9dc135 XL |
390 | // this variable is thread-local, not global. |
391 | dtor_state: Cell<DtorState>, | |
041b39d2 XL |
392 | } |
393 | ||
394 | impl<T> fmt::Debug for Key<T> { | |
532ac7d7 | 395 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
041b39d2 XL |
396 | f.pad("Key { .. }") |
397 | } | |
398 | } | |
399 | ||
041b39d2 XL |
400 | impl<T> Key<T> { |
401 | pub const fn new() -> Key<T> { | |
402 | Key { | |
dc9dc135 XL |
403 | inner: LazyKeyInner::new(), |
404 | dtor_state: Cell::new(DtorState::Unregistered), | |
041b39d2 XL |
405 | } |
406 | } | |
407 | ||
dc9dc135 XL |
408 | pub unsafe fn get<F: FnOnce() -> T>(&self, init: F) -> Option<&'static T> { |
409 | match self.inner.get() { | |
410 | Some(val) => Some(val), | |
411 | None => self.try_initialize(init), | |
041b39d2 | 412 | } |
041b39d2 XL |
413 | } |
414 | ||
dc9dc135 XL |
415 | // `try_initialize` is only called once per fast thread local variable, |
416 | // except in corner cases where thread_local dtors reference other | |
417 | // thread_local's, or it is being recursively initialized. | |
418 | // | |
419 | // Macos: Inlining this function can cause two `tlv_get_addr` calls to | |
420 | // be performed for every call to `Key::get`. The #[cold] hint makes | |
421 | // that less likely. | |
422 | // LLVM issue: https://bugs.llvm.org/show_bug.cgi?id=41722 | |
423 | #[cold] | |
424 | unsafe fn try_initialize<F: FnOnce() -> T>(&self, init: F) -> Option<&'static T> { | |
425 | if !mem::needs_drop::<T>() || self.try_register_dtor() { | |
426 | Some(self.inner.initialize(init)) | |
427 | } else { | |
428 | None | |
041b39d2 | 429 | } |
dc9dc135 | 430 | } |
041b39d2 | 431 | |
dc9dc135 XL |
432 | // `try_register_dtor` is only called once per fast thread local |
433 | // variable, except in corner cases where thread_local dtors reference | |
434 | // other thread_local's, or it is being recursively initialized. | |
435 | unsafe fn try_register_dtor(&self) -> bool { | |
436 | match self.dtor_state.get() { | |
437 | DtorState::Unregistered => { | |
438 | // dtor registration happens before initialization. | |
439 | register_dtor(self as *const _ as *mut u8, | |
440 | destroy_value::<T>); | |
441 | self.dtor_state.set(DtorState::Registered); | |
442 | true | |
443 | } | |
444 | DtorState::Registered => { | |
445 | // recursively initialized | |
446 | true | |
447 | } | |
448 | DtorState::RunningOrHasRun => { | |
449 | false | |
450 | } | |
451 | } | |
041b39d2 XL |
452 | } |
453 | } | |
454 | ||
455 | unsafe extern fn destroy_value<T>(ptr: *mut u8) { | |
456 | let ptr = ptr as *mut Key<T>; | |
041b39d2 | 457 | |
dc9dc135 XL |
458 | // Right before we run the user destructor be sure to set the |
459 | // `Option<T>` to `None`, and `dtor_state` to `RunningOrHasRun`. This | |
460 | // causes future calls to `get` to run `try_initialize_drop` again, | |
461 | // which will now fail, and return `None`. | |
462 | let value = (*ptr).inner.take(); | |
463 | (*ptr).dtor_state.set(DtorState::RunningOrHasRun); | |
464 | drop(value); | |
041b39d2 | 465 | } |
1a4d82fc JJ |
466 | } |
467 | ||
d9579d0f | 468 | #[doc(hidden)] |
9cc50fc6 | 469 | pub mod os { |
dc9dc135 XL |
470 | use super::lazy::LazyKeyInner; |
471 | use crate::cell::Cell; | |
532ac7d7 XL |
472 | use crate::fmt; |
473 | use crate::marker; | |
474 | use crate::ptr; | |
475 | use crate::sys_common::thread_local::StaticKey as OsStaticKey; | |
1a4d82fc | 476 | |
1a4d82fc | 477 | pub struct Key<T> { |
1a4d82fc | 478 | // OS-TLS key that we'll use to key off. |
62682a34 SL |
479 | os: OsStaticKey, |
480 | marker: marker::PhantomData<Cell<T>>, | |
1a4d82fc JJ |
481 | } |
482 | ||
32a655c1 | 483 | impl<T> fmt::Debug for Key<T> { |
532ac7d7 | 484 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
32a655c1 SL |
485 | f.pad("Key { .. }") |
486 | } | |
487 | } | |
488 | ||
532ac7d7 | 489 | unsafe impl<T> Sync for Key<T> { } |
1a4d82fc JJ |
490 | |
491 | struct Value<T: 'static> { | |
dc9dc135 | 492 | inner: LazyKeyInner<T>, |
1a4d82fc | 493 | key: &'static Key<T>, |
1a4d82fc JJ |
494 | } |
495 | ||
62682a34 SL |
496 | impl<T: 'static> Key<T> { |
497 | pub const fn new() -> Key<T> { | |
498 | Key { | |
499 | os: OsStaticKey::new(Some(destroy_value::<T>)), | |
500 | marker: marker::PhantomData | |
501 | } | |
1a4d82fc JJ |
502 | } |
503 | ||
dc9dc135 | 504 | pub unsafe fn get(&'static self, init: fn() -> T) -> Option<&'static T> { |
3b2f2976 | 505 | let ptr = self.os.get() as *mut Value<T>; |
dc9dc135 XL |
506 | if ptr as usize > 1 { |
507 | match (*ptr).inner.get() { | |
508 | Some(ref value) => return Some(value), | |
509 | None => {}, | |
1a4d82fc | 510 | } |
dc9dc135 XL |
511 | } |
512 | self.try_initialize(init) | |
513 | } | |
514 | ||
515 | // `try_initialize` is only called once per os thread local variable, | |
516 | // except in corner cases where thread_local dtors reference other | |
517 | // thread_local's, or it is being recursively initialized. | |
518 | unsafe fn try_initialize(&'static self, init: fn() -> T) -> Option<&'static T> { | |
519 | let ptr = self.os.get() as *mut Value<T>; | |
520 | if ptr as usize == 1 { | |
521 | // destructor is running | |
522 | return None | |
7453a54e | 523 | } |
3b2f2976 | 524 | |
dc9dc135 XL |
525 | let ptr = if ptr.is_null() { |
526 | // If the lookup returned null, we haven't initialized our own | |
527 | // local copy, so do that now. | |
528 | let ptr: Box<Value<T>> = box Value { | |
529 | inner: LazyKeyInner::new(), | |
530 | key: self, | |
531 | }; | |
532 | let ptr = Box::into_raw(ptr); | |
533 | self.os.set(ptr as *mut u8); | |
534 | ptr | |
535 | } else { | |
536 | // recursive initialization | |
537 | ptr | |
3b2f2976 | 538 | }; |
dc9dc135 XL |
539 | |
540 | Some((*ptr).inner.initialize(init)) | |
1a4d82fc JJ |
541 | } |
542 | } | |
543 | ||
041b39d2 | 544 | unsafe extern fn destroy_value<T: 'static>(ptr: *mut u8) { |
1a4d82fc JJ |
545 | // The OS TLS ensures that this key contains a NULL value when this |
546 | // destructor starts to run. We set it back to a sentinel value of 1 to | |
547 | // ensure that any future calls to `get` for this thread will return | |
548 | // `None`. | |
549 | // | |
550 | // Note that to prevent an infinite loop we reset it back to null right | |
551 | // before we return from the destructor ourselves. | |
d9579d0f | 552 | let ptr = Box::from_raw(ptr as *mut Value<T>); |
1a4d82fc JJ |
553 | let key = ptr.key; |
554 | key.os.set(1 as *mut u8); | |
555 | drop(ptr); | |
85aaf69f | 556 | key.os.set(ptr::null_mut()); |
1a4d82fc JJ |
557 | } |
558 | } | |
559 | ||
c30ab7b3 | 560 | #[cfg(all(test, not(target_os = "emscripten")))] |
1a4d82fc | 561 | mod tests { |
532ac7d7 XL |
562 | use crate::sync::mpsc::{channel, Sender}; |
563 | use crate::cell::{Cell, UnsafeCell}; | |
564 | use crate::thread; | |
1a4d82fc JJ |
565 | |
566 | struct Foo(Sender<()>); | |
567 | ||
568 | impl Drop for Foo { | |
569 | fn drop(&mut self) { | |
570 | let Foo(ref s) = *self; | |
571 | s.send(()).unwrap(); | |
572 | } | |
573 | } | |
574 | ||
575 | #[test] | |
576 | fn smoke_no_dtor() { | |
62682a34 | 577 | thread_local!(static FOO: Cell<i32> = Cell::new(1)); |
1a4d82fc | 578 | |
62682a34 SL |
579 | FOO.with(|f| { |
580 | assert_eq!(f.get(), 1); | |
581 | f.set(2); | |
1a4d82fc JJ |
582 | }); |
583 | let (tx, rx) = channel(); | |
85aaf69f | 584 | let _t = thread::spawn(move|| { |
62682a34 SL |
585 | FOO.with(|f| { |
586 | assert_eq!(f.get(), 1); | |
1a4d82fc JJ |
587 | }); |
588 | tx.send(()).unwrap(); | |
589 | }); | |
590 | rx.recv().unwrap(); | |
591 | ||
62682a34 SL |
592 | FOO.with(|f| { |
593 | assert_eq!(f.get(), 2); | |
1a4d82fc JJ |
594 | }); |
595 | } | |
596 | ||
597 | #[test] | |
598 | fn states() { | |
599 | struct Foo; | |
600 | impl Drop for Foo { | |
601 | fn drop(&mut self) { | |
0531ce1d | 602 | assert!(FOO.try_with(|_| ()).is_err()); |
1a4d82fc JJ |
603 | } |
604 | } | |
0531ce1d | 605 | thread_local!(static FOO: Foo = Foo); |
1a4d82fc | 606 | |
85aaf69f | 607 | thread::spawn(|| { |
0531ce1d | 608 | assert!(FOO.try_with(|_| ()).is_ok()); |
532ac7d7 | 609 | }).join().ok().expect("thread panicked"); |
1a4d82fc JJ |
610 | } |
611 | ||
612 | #[test] | |
613 | fn smoke_dtor() { | |
62682a34 | 614 | thread_local!(static FOO: UnsafeCell<Option<Foo>> = UnsafeCell::new(None)); |
1a4d82fc JJ |
615 | |
616 | let (tx, rx) = channel(); | |
85aaf69f | 617 | let _t = thread::spawn(move|| unsafe { |
1a4d82fc JJ |
618 | let mut tx = Some(tx); |
619 | FOO.with(|f| { | |
620 | *f.get() = Some(Foo(tx.take().unwrap())); | |
621 | }); | |
622 | }); | |
623 | rx.recv().unwrap(); | |
624 | } | |
625 | ||
626 | #[test] | |
627 | fn circular() { | |
628 | struct S1; | |
629 | struct S2; | |
62682a34 SL |
630 | thread_local!(static K1: UnsafeCell<Option<S1>> = UnsafeCell::new(None)); |
631 | thread_local!(static K2: UnsafeCell<Option<S2>> = UnsafeCell::new(None)); | |
c34b1796 | 632 | static mut HITS: u32 = 0; |
1a4d82fc JJ |
633 | |
634 | impl Drop for S1 { | |
635 | fn drop(&mut self) { | |
636 | unsafe { | |
637 | HITS += 1; | |
0531ce1d | 638 | if K2.try_with(|_| ()).is_err() { |
1a4d82fc JJ |
639 | assert_eq!(HITS, 3); |
640 | } else { | |
641 | if HITS == 1 { | |
642 | K2.with(|s| *s.get() = Some(S2)); | |
643 | } else { | |
644 | assert_eq!(HITS, 3); | |
645 | } | |
646 | } | |
647 | } | |
648 | } | |
649 | } | |
650 | impl Drop for S2 { | |
651 | fn drop(&mut self) { | |
652 | unsafe { | |
653 | HITS += 1; | |
0531ce1d | 654 | assert!(K1.try_with(|_| ()).is_ok()); |
1a4d82fc JJ |
655 | assert_eq!(HITS, 2); |
656 | K1.with(|s| *s.get() = Some(S1)); | |
657 | } | |
658 | } | |
659 | } | |
660 | ||
85aaf69f | 661 | thread::spawn(move|| { |
1a4d82fc | 662 | drop(S1); |
532ac7d7 | 663 | }).join().ok().expect("thread panicked"); |
1a4d82fc JJ |
664 | } |
665 | ||
666 | #[test] | |
667 | fn self_referential() { | |
668 | struct S1; | |
62682a34 | 669 | thread_local!(static K1: UnsafeCell<Option<S1>> = UnsafeCell::new(None)); |
1a4d82fc JJ |
670 | |
671 | impl Drop for S1 { | |
672 | fn drop(&mut self) { | |
0531ce1d | 673 | assert!(K1.try_with(|_| ()).is_err()); |
1a4d82fc JJ |
674 | } |
675 | } | |
676 | ||
85aaf69f | 677 | thread::spawn(move|| unsafe { |
1a4d82fc | 678 | K1.with(|s| *s.get() = Some(S1)); |
532ac7d7 | 679 | }).join().ok().expect("thread panicked"); |
1a4d82fc JJ |
680 | } |
681 | ||
7453a54e | 682 | // Note that this test will deadlock if TLS destructors aren't run (this |
9fa01778 | 683 | // requires the destructor to be run to pass the test). |
1a4d82fc JJ |
684 | #[test] |
685 | fn dtors_in_dtors_in_dtors() { | |
686 | struct S1(Sender<()>); | |
62682a34 SL |
687 | thread_local!(static K1: UnsafeCell<Option<S1>> = UnsafeCell::new(None)); |
688 | thread_local!(static K2: UnsafeCell<Option<Foo>> = UnsafeCell::new(None)); | |
1a4d82fc JJ |
689 | |
690 | impl Drop for S1 { | |
691 | fn drop(&mut self) { | |
692 | let S1(ref tx) = *self; | |
693 | unsafe { | |
0531ce1d | 694 | let _ = K2.try_with(|s| *s.get() = Some(Foo(tx.clone()))); |
1a4d82fc JJ |
695 | } |
696 | } | |
697 | } | |
698 | ||
699 | let (tx, rx) = channel(); | |
85aaf69f | 700 | let _t = thread::spawn(move|| unsafe { |
1a4d82fc JJ |
701 | let mut tx = Some(tx); |
702 | K1.with(|s| *s.get() = Some(S1(tx.take().unwrap()))); | |
703 | }); | |
704 | rx.recv().unwrap(); | |
705 | } | |
706 | } | |
707 | ||
708 | #[cfg(test)] | |
709 | mod dynamic_tests { | |
532ac7d7 XL |
710 | use crate::cell::RefCell; |
711 | use crate::collections::HashMap; | |
1a4d82fc JJ |
712 | |
713 | #[test] | |
714 | fn smoke() { | |
c34b1796 AL |
715 | fn square(i: i32) -> i32 { i * i } |
716 | thread_local!(static FOO: i32 = square(3)); | |
1a4d82fc JJ |
717 | |
718 | FOO.with(|f| { | |
719 | assert_eq!(*f, 9); | |
720 | }); | |
721 | } | |
722 | ||
723 | #[test] | |
724 | fn hashmap() { | |
c34b1796 | 725 | fn map() -> RefCell<HashMap<i32, i32>> { |
1a4d82fc JJ |
726 | let mut m = HashMap::new(); |
727 | m.insert(1, 2); | |
728 | RefCell::new(m) | |
729 | } | |
c34b1796 | 730 | thread_local!(static FOO: RefCell<HashMap<i32, i32>> = map()); |
1a4d82fc JJ |
731 | |
732 | FOO.with(|map| { | |
c34b1796 | 733 | assert_eq!(map.borrow()[&1], 2); |
1a4d82fc JJ |
734 | }); |
735 | } | |
736 | ||
737 | #[test] | |
738 | fn refcell_vec() { | |
c34b1796 | 739 | thread_local!(static FOO: RefCell<Vec<u32>> = RefCell::new(vec![1, 2, 3])); |
1a4d82fc JJ |
740 | |
741 | FOO.with(|vec| { | |
742 | assert_eq!(vec.borrow().len(), 3); | |
743 | vec.borrow_mut().push(4); | |
744 | assert_eq!(vec.borrow()[3], 4); | |
745 | }); | |
746 | } | |
747 | } |