]>
Commit | Line | Data |
---|---|---|
1a4d82fc | 1 | //! Thread local storage |
c34b1796 | 2 | |
dfeec247 | 3 | #![unstable(feature = "thread_local_internals", issue = "none")] |
1a4d82fc | 4 | |
416331ca | 5 | use crate::error::Error; |
532ac7d7 | 6 | use crate::fmt; |
1a4d82fc JJ |
7 | |
8 | /// A thread local storage key which owns its contents. | |
9 | /// | |
10 | /// This key uses the fastest possible implementation available to it for the | |
7cac9316 XL |
11 | /// target platform. It is instantiated with the [`thread_local!`] macro and the |
12 | /// primary method is the [`with`] method. | |
1a4d82fc | 13 | /// |
7cac9316 | 14 | /// The [`with`] method yields a reference to the contained value which cannot be |
bd371182 | 15 | /// sent across threads or escape the given closure. |
1a4d82fc JJ |
16 | /// |
17 | /// # Initialization and Destruction | |
18 | /// | |
7cac9316 XL |
19 | /// Initialization is dynamically performed on the first call to [`with`] |
20 | /// within a thread, and values that implement [`Drop`] get destructed when a | |
8bb4bdeb | 21 | /// thread exits. Some caveats apply, which are explained below. |
1a4d82fc | 22 | /// |
ea8adc8c XL |
23 | /// A `LocalKey`'s initializer cannot recursively depend on itself, and using |
24 | /// a `LocalKey` in this way will cause the initializer to infinitely recurse | |
25 | /// on the first call to `with`. | |
26 | /// | |
c34b1796 | 27 | /// # Examples |
1a4d82fc JJ |
28 | /// |
29 | /// ``` | |
30 | /// use std::cell::RefCell; | |
85aaf69f | 31 | /// use std::thread; |
1a4d82fc | 32 | /// |
c34b1796 | 33 | /// thread_local!(static FOO: RefCell<u32> = RefCell::new(1)); |
1a4d82fc JJ |
34 | /// |
35 | /// FOO.with(|f| { | |
36 | /// assert_eq!(*f.borrow(), 1); | |
37 | /// *f.borrow_mut() = 2; | |
38 | /// }); | |
39 | /// | |
40 | /// // each thread starts out with the initial value of 1 | |
532ac7d7 | 41 | /// let t = thread::spawn(move|| { |
1a4d82fc JJ |
42 | /// FOO.with(|f| { |
43 | /// assert_eq!(*f.borrow(), 1); | |
44 | /// *f.borrow_mut() = 3; | |
45 | /// }); | |
46 | /// }); | |
47 | /// | |
532ac7d7 XL |
48 | /// // wait for the thread to complete and bail out on panic |
49 | /// t.join().unwrap(); | |
50 | /// | |
1a4d82fc JJ |
51 | /// // we retain our original value of 2 despite the child thread |
52 | /// FOO.with(|f| { | |
53 | /// assert_eq!(*f.borrow(), 2); | |
54 | /// }); | |
55 | /// ``` | |
7453a54e SL |
56 | /// |
57 | /// # Platform-specific behavior | |
58 | /// | |
59 | /// Note that a "best effort" is made to ensure that destructors for types | |
a7813a04 | 60 | /// stored in thread local storage are run, but not all platforms can guarantee |
7453a54e SL |
61 | /// that destructors will be run for all types in thread local storage. For |
62 | /// example, there are a number of known caveats where destructors are not run: | |
63 | /// | |
64 | /// 1. On Unix systems when pthread-based TLS is being used, destructors will | |
65 | /// not be run for TLS values on the main thread when it exits. Note that the | |
66 | /// application will exit immediately after the main thread exits as well. | |
67 | /// 2. On all platforms it's possible for TLS to re-initialize other TLS slots | |
68 | /// during destruction. Some platforms ensure that this cannot happen | |
69 | /// infinitely by preventing re-initialization of any slot that has been | |
70 | /// destroyed, but not all platforms have this guard. Those platforms that do | |
71 | /// not guard typically have a synthetic limit after which point no more | |
72 | /// destructors are run. | |
7cac9316 XL |
73 | /// |
74 | /// [`with`]: ../../std/thread/struct.LocalKey.html#method.with | |
75 | /// [`thread_local!`]: ../../std/macro.thread_local.html | |
76 | /// [`Drop`]: ../../std/ops/trait.Drop.html | |
85aaf69f | 77 | #[stable(feature = "rust1", since = "1.0.0")] |
9cc50fc6 SL |
78 | pub struct LocalKey<T: 'static> { |
79 | // This outer `LocalKey<T>` type is what's going to be stored in statics, | |
80 | // but actual data inside will sometimes be tagged with #[thread_local]. | |
81 | // It's not valid for a true static to reference a #[thread_local] static, | |
82 | // so we get around that by exposing an accessor through a layer of function | |
83 | // indirection (this thunk). | |
1a4d82fc | 84 | // |
9cc50fc6 SL |
85 | // Note that the thunk is itself unsafe because the returned lifetime of the |
86 | // slot where data lives, `'static`, is not actually valid. The lifetime | |
3b2f2976 | 87 | // here is actually slightly shorter than the currently running thread! |
9cc50fc6 SL |
88 | // |
89 | // Although this is an extra layer of indirection, it should in theory be | |
90 | // trivially devirtualizable by LLVM because the value of `inner` never | |
91 | // changes and the constant should be readonly within a crate. This mainly | |
92 | // only runs into problems when TLS statics are exported across crates. | |
dc9dc135 | 93 | inner: unsafe fn() -> Option<&'static T>, |
1a4d82fc JJ |
94 | } |
95 | ||
8bb4bdeb | 96 | #[stable(feature = "std_debug", since = "1.16.0")] |
32a655c1 | 97 | impl<T: 'static> fmt::Debug for LocalKey<T> { |
532ac7d7 | 98 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
32a655c1 SL |
99 | f.pad("LocalKey { .. }") |
100 | } | |
101 | } | |
102 | ||
7cac9316 | 103 | /// Declare a new thread local storage key of type [`std::thread::LocalKey`]. |
62682a34 | 104 | /// |
3157f602 XL |
105 | /// # Syntax |
106 | /// | |
107 | /// The macro wraps any number of static declarations and makes them thread local. | |
041b39d2 | 108 | /// Publicity and attributes for each static are allowed. Example: |
3157f602 XL |
109 | /// |
110 | /// ``` | |
111 | /// use std::cell::RefCell; | |
112 | /// thread_local! { | |
113 | /// pub static FOO: RefCell<u32> = RefCell::new(1); | |
114 | /// | |
115 | /// #[allow(unused)] | |
116 | /// static BAR: RefCell<f32> = RefCell::new(1.0); | |
117 | /// } | |
118 | /// # fn main() {} | |
119 | /// ``` | |
120 | /// | |
7cac9316 | 121 | /// See [LocalKey documentation][`std::thread::LocalKey`] for more |
62682a34 | 122 | /// information. |
7cac9316 XL |
123 | /// |
124 | /// [`std::thread::LocalKey`]: ../std/thread/struct.LocalKey.html | |
1a4d82fc | 125 | #[macro_export] |
62682a34 | 126 | #[stable(feature = "rust1", since = "1.0.0")] |
532ac7d7 | 127 | #[allow_internal_unstable(thread_local_internals)] |
041b39d2 XL |
128 | macro_rules! thread_local { |
129 | // empty (base case for the recursion) | |
130 | () => {}; | |
131 | ||
132 | // process multiple declarations | |
133 | ($(#[$attr:meta])* $vis:vis static $name:ident: $t:ty = $init:expr; $($rest:tt)*) => ( | |
a1dfa0c6 XL |
134 | $crate::__thread_local_inner!($(#[$attr])* $vis $name, $t, $init); |
135 | $crate::thread_local!($($rest)*); | |
041b39d2 XL |
136 | ); |
137 | ||
138 | // handle a single declaration | |
139 | ($(#[$attr:meta])* $vis:vis static $name:ident: $t:ty = $init:expr) => ( | |
a1dfa0c6 | 140 | $crate::__thread_local_inner!($(#[$attr])* $vis $name, $t, $init); |
041b39d2 XL |
141 | ); |
142 | } | |
143 | ||
041b39d2 | 144 | #[doc(hidden)] |
dfeec247 | 145 | #[unstable(feature = "thread_local_internals", reason = "should not be necessary", issue = "none")] |
041b39d2 | 146 | #[macro_export] |
532ac7d7 | 147 | #[allow_internal_unstable(thread_local_internals, cfg_target_thread_local, thread_local)] |
ea8adc8c | 148 | #[allow_internal_unsafe] |
041b39d2 | 149 | macro_rules! __thread_local_inner { |
60c5eb7d | 150 | (@key $t:ty, $init:expr) => { |
ea8adc8c XL |
151 | { |
152 | #[inline] | |
041b39d2 XL |
153 | fn __init() -> $t { $init } |
154 | ||
dc9dc135 | 155 | unsafe fn __getit() -> $crate::option::Option<&'static $t> { |
0bf4aa26 | 156 | #[cfg(all(target_arch = "wasm32", not(target_feature = "atomics")))] |
83c7162d XL |
157 | static __KEY: $crate::thread::__StaticLocalKeyInner<$t> = |
158 | $crate::thread::__StaticLocalKeyInner::new(); | |
159 | ||
041b39d2 | 160 | #[thread_local] |
0bf4aa26 XL |
161 | #[cfg(all( |
162 | target_thread_local, | |
163 | not(all(target_arch = "wasm32", not(target_feature = "atomics"))), | |
164 | ))] | |
041b39d2 XL |
165 | static __KEY: $crate::thread::__FastLocalKeyInner<$t> = |
166 | $crate::thread::__FastLocalKeyInner::new(); | |
167 | ||
0bf4aa26 XL |
168 | #[cfg(all( |
169 | not(target_thread_local), | |
170 | not(all(target_arch = "wasm32", not(target_feature = "atomics"))), | |
171 | ))] | |
041b39d2 XL |
172 | static __KEY: $crate::thread::__OsLocalKeyInner<$t> = |
173 | $crate::thread::__OsLocalKeyInner::new(); | |
174 | ||
dc9dc135 | 175 | __KEY.get(__init) |
041b39d2 XL |
176 | } |
177 | ||
3b2f2976 | 178 | unsafe { |
dc9dc135 | 179 | $crate::thread::LocalKey::new(__getit) |
3b2f2976 | 180 | } |
ea8adc8c XL |
181 | } |
182 | }; | |
183 | ($(#[$attr:meta])* $vis:vis $name:ident, $t:ty, $init:expr) => { | |
ea8adc8c | 184 | $(#[$attr])* $vis const $name: $crate::thread::LocalKey<$t> = |
60c5eb7d | 185 | $crate::__thread_local_inner!(@key $t, $init); |
041b39d2 XL |
186 | } |
187 | } | |
188 | ||
041b39d2 | 189 | /// An error returned by [`LocalKey::try_with`](struct.LocalKey.html#method.try_with). |
0531ce1d | 190 | #[stable(feature = "thread_local_try_with", since = "1.26.0")] |
416331ca | 191 | #[derive(Clone, Copy, Eq, PartialEq)] |
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 | ||
416331ca XL |
210 | #[stable(feature = "thread_local_try_with", since = "1.26.0")] |
211 | impl Error for AccessError {} | |
212 | ||
c34b1796 | 213 | impl<T: 'static> LocalKey<T> { |
62682a34 | 214 | #[doc(hidden)] |
60c5eb7d XL |
215 | #[unstable( |
216 | feature = "thread_local_internals", | |
217 | reason = "recently added to create a key", | |
dfeec247 | 218 | issue = "none" |
60c5eb7d | 219 | )] |
dc9dc135 | 220 | pub const unsafe fn new(inner: unsafe fn() -> Option<&'static T>) -> LocalKey<T> { |
60c5eb7d | 221 | LocalKey { inner } |
62682a34 SL |
222 | } |
223 | ||
9346a6ac | 224 | /// Acquires a reference to the value in this TLS key. |
1a4d82fc JJ |
225 | /// |
226 | /// This will lazily initialize the value if this thread has not referenced | |
227 | /// this key yet. | |
228 | /// | |
229 | /// # Panics | |
230 | /// | |
231 | /// This function will `panic!()` if the key currently has its | |
232 | /// destructor running, and it **may** panic if the destructor has | |
233 | /// previously been run for this thread. | |
85aaf69f | 234 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 235 | pub fn with<F, R>(&'static self, f: F) -> R |
60c5eb7d XL |
236 | where |
237 | F: FnOnce(&T) -> R, | |
238 | { | |
239 | self.try_with(f).expect( | |
240 | "cannot access a Thread Local Storage value \ | |
241 | during or after destruction", | |
242 | ) | |
1a4d82fc JJ |
243 | } |
244 | ||
041b39d2 XL |
245 | /// Acquires a reference to the value in this TLS key. |
246 | /// | |
247 | /// This will lazily initialize the value if this thread has not referenced | |
248 | /// this key yet. If the key has been destroyed (which may happen if this is called | |
8faf50e0 | 249 | /// in a destructor), this function will return an [`AccessError`](struct.AccessError.html). |
041b39d2 XL |
250 | /// |
251 | /// # Panics | |
252 | /// | |
253 | /// This function will still `panic!()` if the key is uninitialized and the | |
254 | /// key's initializer panics. | |
0531ce1d | 255 | #[stable(feature = "thread_local_try_with", since = "1.26.0")] |
041b39d2 | 256 | pub fn try_with<F, R>(&'static self, f: F) -> Result<R, AccessError> |
0531ce1d XL |
257 | where |
258 | F: FnOnce(&T) -> R, | |
259 | { | |
041b39d2 | 260 | unsafe { |
60c5eb7d | 261 | let thread_local = (self.inner)().ok_or(AccessError { _private: () })?; |
dc9dc135 XL |
262 | Ok(f(thread_local)) |
263 | } | |
264 | } | |
265 | } | |
266 | ||
267 | mod lazy { | |
268 | use crate::cell::UnsafeCell; | |
dc9dc135 | 269 | use crate::hint; |
60c5eb7d | 270 | use crate::mem; |
dc9dc135 XL |
271 | |
272 | pub struct LazyKeyInner<T> { | |
273 | inner: UnsafeCell<Option<T>>, | |
274 | } | |
275 | ||
276 | impl<T> LazyKeyInner<T> { | |
277 | pub const fn new() -> LazyKeyInner<T> { | |
60c5eb7d | 278 | LazyKeyInner { inner: UnsafeCell::new(None) } |
dc9dc135 XL |
279 | } |
280 | ||
281 | pub unsafe fn get(&self) -> Option<&'static T> { | |
282 | (*self.inner.get()).as_ref() | |
283 | } | |
284 | ||
285 | pub unsafe fn initialize<F: FnOnce() -> T>(&self, init: F) -> &'static T { | |
286 | // Execute the initialization up front, *then* move it into our slot, | |
287 | // just in case initialization fails. | |
288 | let value = init(); | |
289 | let ptr = self.inner.get(); | |
290 | ||
291 | // note that this can in theory just be `*ptr = Some(value)`, but due to | |
292 | // the compiler will currently codegen that pattern with something like: | |
293 | // | |
294 | // ptr::drop_in_place(ptr) | |
295 | // ptr::write(ptr, Some(value)) | |
296 | // | |
297 | // Due to this pattern it's possible for the destructor of the value in | |
298 | // `ptr` (e.g., if this is being recursively initialized) to re-access | |
299 | // TLS, in which case there will be a `&` and `&mut` pointer to the same | |
300 | // value (an aliasing violation). To avoid setting the "I'm running a | |
301 | // destructor" flag we just use `mem::replace` which should sequence the | |
302 | // operations a little differently and make this safe to call. | |
303 | mem::replace(&mut *ptr, Some(value)); | |
304 | ||
305 | // After storing `Some` we want to get a reference to the contents of | |
306 | // what we just stored. While we could use `unwrap` here and it should | |
307 | // always work it empirically doesn't seem to always get optimized away, | |
308 | // which means that using something like `try_with` can pull in | |
309 | // panicking code and cause a large size bloat. | |
310 | match *ptr { | |
311 | Some(ref x) => x, | |
312 | None => hint::unreachable_unchecked(), | |
313 | } | |
314 | } | |
315 | ||
316 | #[allow(unused)] | |
317 | pub unsafe fn take(&mut self) -> Option<T> { | |
318 | (*self.inner.get()).take() | |
041b39d2 XL |
319 | } |
320 | } | |
321 | } | |
322 | ||
83c7162d XL |
323 | /// On some platforms like wasm32 there's no threads, so no need to generate |
324 | /// thread locals and we can instead just use plain statics! | |
325 | #[doc(hidden)] | |
0bf4aa26 | 326 | #[cfg(all(target_arch = "wasm32", not(target_feature = "atomics")))] |
83c7162d | 327 | pub mod statik { |
dc9dc135 | 328 | use super::lazy::LazyKeyInner; |
532ac7d7 | 329 | use crate::fmt; |
83c7162d XL |
330 | |
331 | pub struct Key<T> { | |
dc9dc135 | 332 | inner: LazyKeyInner<T>, |
83c7162d XL |
333 | } |
334 | ||
60c5eb7d | 335 | unsafe impl<T> Sync for Key<T> {} |
83c7162d XL |
336 | |
337 | impl<T> fmt::Debug for Key<T> { | |
532ac7d7 | 338 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
83c7162d XL |
339 | f.pad("Key { .. }") |
340 | } | |
341 | } | |
342 | ||
343 | impl<T> Key<T> { | |
344 | pub const fn new() -> Key<T> { | |
60c5eb7d | 345 | Key { inner: LazyKeyInner::new() } |
83c7162d XL |
346 | } |
347 | ||
dc9dc135 XL |
348 | pub unsafe fn get(&self, init: fn() -> T) -> Option<&'static T> { |
349 | let value = match self.inner.get() { | |
350 | Some(ref value) => value, | |
351 | None => self.inner.initialize(init), | |
352 | }; | |
353 | Some(value) | |
83c7162d XL |
354 | } |
355 | } | |
356 | } | |
357 | ||
041b39d2 XL |
358 | #[doc(hidden)] |
359 | #[cfg(target_thread_local)] | |
360 | pub mod fast { | |
dc9dc135 XL |
361 | use super::lazy::LazyKeyInner; |
362 | use crate::cell::Cell; | |
532ac7d7 XL |
363 | use crate::fmt; |
364 | use crate::mem; | |
dc9dc135 | 365 | use crate::sys::fast_thread_local::register_dtor; |
041b39d2 | 366 | |
dc9dc135 XL |
367 | #[derive(Copy, Clone)] |
368 | enum DtorState { | |
369 | Unregistered, | |
370 | Registered, | |
371 | RunningOrHasRun, | |
372 | } | |
373 | ||
374 | // This data structure has been carefully constructed so that the fast path | |
375 | // only contains one branch on x86. That optimization is necessary to avoid | |
376 | // duplicated tls lookups on OSX. | |
377 | // | |
378 | // LLVM issue: https://bugs.llvm.org/show_bug.cgi?id=41722 | |
041b39d2 | 379 | pub struct Key<T> { |
dc9dc135 XL |
380 | // If `LazyKeyInner::get` returns `None`, that indicates either: |
381 | // * The value has never been initialized | |
382 | // * The value is being recursively initialized | |
383 | // * The value has already been destroyed or is being destroyed | |
384 | // To determine which kind of `None`, check `dtor_state`. | |
385 | // | |
386 | // This is very optimizer friendly for the fast path - initialized but | |
387 | // not yet dropped. | |
388 | inner: LazyKeyInner<T>, | |
041b39d2 XL |
389 | |
390 | // Metadata to keep track of the state of the destructor. Remember that | |
dc9dc135 XL |
391 | // this variable is thread-local, not global. |
392 | dtor_state: Cell<DtorState>, | |
041b39d2 XL |
393 | } |
394 | ||
395 | impl<T> fmt::Debug for Key<T> { | |
532ac7d7 | 396 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
041b39d2 XL |
397 | f.pad("Key { .. }") |
398 | } | |
399 | } | |
400 | ||
041b39d2 XL |
401 | impl<T> Key<T> { |
402 | pub const fn new() -> Key<T> { | |
60c5eb7d | 403 | Key { inner: LazyKeyInner::new(), dtor_state: Cell::new(DtorState::Unregistered) } |
041b39d2 XL |
404 | } |
405 | ||
dc9dc135 XL |
406 | pub unsafe fn get<F: FnOnce() -> T>(&self, init: F) -> Option<&'static T> { |
407 | match self.inner.get() { | |
408 | Some(val) => Some(val), | |
409 | None => self.try_initialize(init), | |
041b39d2 | 410 | } |
041b39d2 XL |
411 | } |
412 | ||
dc9dc135 XL |
413 | // `try_initialize` is only called once per fast thread local variable, |
414 | // except in corner cases where thread_local dtors reference other | |
415 | // thread_local's, or it is being recursively initialized. | |
416 | // | |
417 | // Macos: Inlining this function can cause two `tlv_get_addr` calls to | |
418 | // be performed for every call to `Key::get`. The #[cold] hint makes | |
419 | // that less likely. | |
420 | // LLVM issue: https://bugs.llvm.org/show_bug.cgi?id=41722 | |
421 | #[cold] | |
422 | unsafe fn try_initialize<F: FnOnce() -> T>(&self, init: F) -> Option<&'static T> { | |
423 | if !mem::needs_drop::<T>() || self.try_register_dtor() { | |
424 | Some(self.inner.initialize(init)) | |
425 | } else { | |
426 | None | |
041b39d2 | 427 | } |
dc9dc135 | 428 | } |
041b39d2 | 429 | |
dc9dc135 XL |
430 | // `try_register_dtor` is only called once per fast thread local |
431 | // variable, except in corner cases where thread_local dtors reference | |
432 | // other thread_local's, or it is being recursively initialized. | |
433 | unsafe fn try_register_dtor(&self) -> bool { | |
434 | match self.dtor_state.get() { | |
435 | DtorState::Unregistered => { | |
436 | // dtor registration happens before initialization. | |
60c5eb7d | 437 | register_dtor(self as *const _ as *mut u8, destroy_value::<T>); |
dc9dc135 XL |
438 | self.dtor_state.set(DtorState::Registered); |
439 | true | |
440 | } | |
441 | DtorState::Registered => { | |
442 | // recursively initialized | |
443 | true | |
444 | } | |
60c5eb7d | 445 | DtorState::RunningOrHasRun => false, |
dc9dc135 | 446 | } |
041b39d2 XL |
447 | } |
448 | } | |
449 | ||
60c5eb7d | 450 | unsafe extern "C" fn destroy_value<T>(ptr: *mut u8) { |
041b39d2 | 451 | let ptr = ptr as *mut Key<T>; |
041b39d2 | 452 | |
dc9dc135 XL |
453 | // Right before we run the user destructor be sure to set the |
454 | // `Option<T>` to `None`, and `dtor_state` to `RunningOrHasRun`. This | |
455 | // causes future calls to `get` to run `try_initialize_drop` again, | |
456 | // which will now fail, and return `None`. | |
457 | let value = (*ptr).inner.take(); | |
458 | (*ptr).dtor_state.set(DtorState::RunningOrHasRun); | |
459 | drop(value); | |
041b39d2 | 460 | } |
1a4d82fc JJ |
461 | } |
462 | ||
d9579d0f | 463 | #[doc(hidden)] |
9cc50fc6 | 464 | pub mod os { |
dc9dc135 XL |
465 | use super::lazy::LazyKeyInner; |
466 | use crate::cell::Cell; | |
532ac7d7 XL |
467 | use crate::fmt; |
468 | use crate::marker; | |
469 | use crate::ptr; | |
470 | use crate::sys_common::thread_local::StaticKey as OsStaticKey; | |
1a4d82fc | 471 | |
1a4d82fc | 472 | pub struct Key<T> { |
1a4d82fc | 473 | // OS-TLS key that we'll use to key off. |
62682a34 SL |
474 | os: OsStaticKey, |
475 | marker: marker::PhantomData<Cell<T>>, | |
1a4d82fc JJ |
476 | } |
477 | ||
32a655c1 | 478 | impl<T> fmt::Debug for Key<T> { |
532ac7d7 | 479 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
32a655c1 SL |
480 | f.pad("Key { .. }") |
481 | } | |
482 | } | |
483 | ||
60c5eb7d | 484 | unsafe impl<T> Sync for Key<T> {} |
1a4d82fc JJ |
485 | |
486 | struct Value<T: 'static> { | |
dc9dc135 | 487 | inner: LazyKeyInner<T>, |
1a4d82fc | 488 | key: &'static Key<T>, |
1a4d82fc JJ |
489 | } |
490 | ||
62682a34 SL |
491 | impl<T: 'static> Key<T> { |
492 | pub const fn new() -> Key<T> { | |
60c5eb7d | 493 | Key { os: OsStaticKey::new(Some(destroy_value::<T>)), marker: marker::PhantomData } |
1a4d82fc JJ |
494 | } |
495 | ||
dc9dc135 | 496 | pub unsafe fn get(&'static self, init: fn() -> T) -> Option<&'static T> { |
3b2f2976 | 497 | let ptr = self.os.get() as *mut Value<T>; |
dc9dc135 | 498 | if ptr as usize > 1 { |
e74abb32 XL |
499 | if let Some(ref value) = (*ptr).inner.get() { |
500 | return Some(value); | |
1a4d82fc | 501 | } |
dc9dc135 XL |
502 | } |
503 | self.try_initialize(init) | |
504 | } | |
505 | ||
506 | // `try_initialize` is only called once per os thread local variable, | |
507 | // except in corner cases where thread_local dtors reference other | |
508 | // thread_local's, or it is being recursively initialized. | |
509 | unsafe fn try_initialize(&'static self, init: fn() -> T) -> Option<&'static T> { | |
510 | let ptr = self.os.get() as *mut Value<T>; | |
511 | if ptr as usize == 1 { | |
512 | // destructor is running | |
60c5eb7d | 513 | return None; |
7453a54e | 514 | } |
3b2f2976 | 515 | |
dc9dc135 XL |
516 | let ptr = if ptr.is_null() { |
517 | // If the lookup returned null, we haven't initialized our own | |
518 | // local copy, so do that now. | |
60c5eb7d | 519 | let ptr: Box<Value<T>> = box Value { inner: LazyKeyInner::new(), key: self }; |
dc9dc135 XL |
520 | let ptr = Box::into_raw(ptr); |
521 | self.os.set(ptr as *mut u8); | |
522 | ptr | |
523 | } else { | |
524 | // recursive initialization | |
525 | ptr | |
3b2f2976 | 526 | }; |
dc9dc135 XL |
527 | |
528 | Some((*ptr).inner.initialize(init)) | |
1a4d82fc JJ |
529 | } |
530 | } | |
531 | ||
60c5eb7d | 532 | unsafe extern "C" fn destroy_value<T: 'static>(ptr: *mut u8) { |
1a4d82fc JJ |
533 | // The OS TLS ensures that this key contains a NULL value when this |
534 | // destructor starts to run. We set it back to a sentinel value of 1 to | |
535 | // ensure that any future calls to `get` for this thread will return | |
536 | // `None`. | |
537 | // | |
538 | // Note that to prevent an infinite loop we reset it back to null right | |
539 | // before we return from the destructor ourselves. | |
d9579d0f | 540 | let ptr = Box::from_raw(ptr as *mut Value<T>); |
1a4d82fc JJ |
541 | let key = ptr.key; |
542 | key.os.set(1 as *mut u8); | |
543 | drop(ptr); | |
85aaf69f | 544 | key.os.set(ptr::null_mut()); |
1a4d82fc JJ |
545 | } |
546 | } | |
547 | ||
c30ab7b3 | 548 | #[cfg(all(test, not(target_os = "emscripten")))] |
1a4d82fc | 549 | mod tests { |
532ac7d7 | 550 | use crate::cell::{Cell, UnsafeCell}; |
60c5eb7d | 551 | use crate::sync::mpsc::{channel, Sender}; |
532ac7d7 | 552 | use crate::thread; |
1a4d82fc JJ |
553 | |
554 | struct Foo(Sender<()>); | |
555 | ||
556 | impl Drop for Foo { | |
557 | fn drop(&mut self) { | |
558 | let Foo(ref s) = *self; | |
559 | s.send(()).unwrap(); | |
560 | } | |
561 | } | |
562 | ||
563 | #[test] | |
564 | fn smoke_no_dtor() { | |
62682a34 | 565 | thread_local!(static FOO: Cell<i32> = Cell::new(1)); |
1a4d82fc | 566 | |
62682a34 SL |
567 | FOO.with(|f| { |
568 | assert_eq!(f.get(), 1); | |
569 | f.set(2); | |
1a4d82fc JJ |
570 | }); |
571 | let (tx, rx) = channel(); | |
60c5eb7d | 572 | let _t = thread::spawn(move || { |
62682a34 SL |
573 | FOO.with(|f| { |
574 | assert_eq!(f.get(), 1); | |
1a4d82fc JJ |
575 | }); |
576 | tx.send(()).unwrap(); | |
577 | }); | |
578 | rx.recv().unwrap(); | |
579 | ||
62682a34 SL |
580 | FOO.with(|f| { |
581 | assert_eq!(f.get(), 2); | |
1a4d82fc JJ |
582 | }); |
583 | } | |
584 | ||
585 | #[test] | |
586 | fn states() { | |
587 | struct Foo; | |
588 | impl Drop for Foo { | |
589 | fn drop(&mut self) { | |
0531ce1d | 590 | assert!(FOO.try_with(|_| ()).is_err()); |
1a4d82fc JJ |
591 | } |
592 | } | |
0531ce1d | 593 | thread_local!(static FOO: Foo = Foo); |
1a4d82fc | 594 | |
85aaf69f | 595 | thread::spawn(|| { |
0531ce1d | 596 | assert!(FOO.try_with(|_| ()).is_ok()); |
60c5eb7d XL |
597 | }) |
598 | .join() | |
599 | .ok() | |
600 | .expect("thread panicked"); | |
1a4d82fc JJ |
601 | } |
602 | ||
603 | #[test] | |
604 | fn smoke_dtor() { | |
62682a34 | 605 | thread_local!(static FOO: UnsafeCell<Option<Foo>> = UnsafeCell::new(None)); |
1a4d82fc JJ |
606 | |
607 | let (tx, rx) = channel(); | |
60c5eb7d | 608 | let _t = thread::spawn(move || unsafe { |
1a4d82fc JJ |
609 | let mut tx = Some(tx); |
610 | FOO.with(|f| { | |
611 | *f.get() = Some(Foo(tx.take().unwrap())); | |
612 | }); | |
613 | }); | |
614 | rx.recv().unwrap(); | |
615 | } | |
616 | ||
617 | #[test] | |
618 | fn circular() { | |
619 | struct S1; | |
620 | struct S2; | |
62682a34 SL |
621 | thread_local!(static K1: UnsafeCell<Option<S1>> = UnsafeCell::new(None)); |
622 | thread_local!(static K2: UnsafeCell<Option<S2>> = UnsafeCell::new(None)); | |
c34b1796 | 623 | static mut HITS: u32 = 0; |
1a4d82fc JJ |
624 | |
625 | impl Drop for S1 { | |
626 | fn drop(&mut self) { | |
627 | unsafe { | |
628 | HITS += 1; | |
0531ce1d | 629 | if K2.try_with(|_| ()).is_err() { |
1a4d82fc JJ |
630 | assert_eq!(HITS, 3); |
631 | } else { | |
632 | if HITS == 1 { | |
633 | K2.with(|s| *s.get() = Some(S2)); | |
634 | } else { | |
635 | assert_eq!(HITS, 3); | |
636 | } | |
637 | } | |
638 | } | |
639 | } | |
640 | } | |
641 | impl Drop for S2 { | |
642 | fn drop(&mut self) { | |
643 | unsafe { | |
644 | HITS += 1; | |
0531ce1d | 645 | assert!(K1.try_with(|_| ()).is_ok()); |
1a4d82fc JJ |
646 | assert_eq!(HITS, 2); |
647 | K1.with(|s| *s.get() = Some(S1)); | |
648 | } | |
649 | } | |
650 | } | |
651 | ||
60c5eb7d | 652 | thread::spawn(move || { |
1a4d82fc | 653 | drop(S1); |
60c5eb7d XL |
654 | }) |
655 | .join() | |
656 | .ok() | |
657 | .expect("thread panicked"); | |
1a4d82fc JJ |
658 | } |
659 | ||
660 | #[test] | |
661 | fn self_referential() { | |
662 | struct S1; | |
62682a34 | 663 | thread_local!(static K1: UnsafeCell<Option<S1>> = UnsafeCell::new(None)); |
1a4d82fc JJ |
664 | |
665 | impl Drop for S1 { | |
666 | fn drop(&mut self) { | |
0531ce1d | 667 | assert!(K1.try_with(|_| ()).is_err()); |
1a4d82fc JJ |
668 | } |
669 | } | |
670 | ||
60c5eb7d | 671 | thread::spawn(move || unsafe { |
1a4d82fc | 672 | K1.with(|s| *s.get() = Some(S1)); |
60c5eb7d XL |
673 | }) |
674 | .join() | |
675 | .ok() | |
676 | .expect("thread panicked"); | |
1a4d82fc JJ |
677 | } |
678 | ||
7453a54e | 679 | // Note that this test will deadlock if TLS destructors aren't run (this |
9fa01778 | 680 | // requires the destructor to be run to pass the test). |
1a4d82fc JJ |
681 | #[test] |
682 | fn dtors_in_dtors_in_dtors() { | |
683 | struct S1(Sender<()>); | |
62682a34 SL |
684 | thread_local!(static K1: UnsafeCell<Option<S1>> = UnsafeCell::new(None)); |
685 | thread_local!(static K2: UnsafeCell<Option<Foo>> = UnsafeCell::new(None)); | |
1a4d82fc JJ |
686 | |
687 | impl Drop for S1 { | |
688 | fn drop(&mut self) { | |
689 | let S1(ref tx) = *self; | |
690 | unsafe { | |
0531ce1d | 691 | let _ = K2.try_with(|s| *s.get() = Some(Foo(tx.clone()))); |
1a4d82fc JJ |
692 | } |
693 | } | |
694 | } | |
695 | ||
696 | let (tx, rx) = channel(); | |
60c5eb7d | 697 | let _t = thread::spawn(move || unsafe { |
1a4d82fc JJ |
698 | let mut tx = Some(tx); |
699 | K1.with(|s| *s.get() = Some(S1(tx.take().unwrap()))); | |
700 | }); | |
701 | rx.recv().unwrap(); | |
702 | } | |
703 | } | |
704 | ||
705 | #[cfg(test)] | |
706 | mod dynamic_tests { | |
532ac7d7 XL |
707 | use crate::cell::RefCell; |
708 | use crate::collections::HashMap; | |
1a4d82fc JJ |
709 | |
710 | #[test] | |
711 | fn smoke() { | |
60c5eb7d XL |
712 | fn square(i: i32) -> i32 { |
713 | i * i | |
714 | } | |
c34b1796 | 715 | thread_local!(static FOO: i32 = square(3)); |
1a4d82fc JJ |
716 | |
717 | FOO.with(|f| { | |
718 | assert_eq!(*f, 9); | |
719 | }); | |
720 | } | |
721 | ||
722 | #[test] | |
723 | fn hashmap() { | |
c34b1796 | 724 | fn map() -> RefCell<HashMap<i32, i32>> { |
1a4d82fc JJ |
725 | let mut m = HashMap::new(); |
726 | m.insert(1, 2); | |
727 | RefCell::new(m) | |
728 | } | |
c34b1796 | 729 | thread_local!(static FOO: RefCell<HashMap<i32, i32>> = map()); |
1a4d82fc JJ |
730 | |
731 | FOO.with(|map| { | |
c34b1796 | 732 | assert_eq!(map.borrow()[&1], 2); |
1a4d82fc JJ |
733 | }); |
734 | } | |
735 | ||
736 | #[test] | |
737 | fn refcell_vec() { | |
c34b1796 | 738 | thread_local!(static FOO: RefCell<Vec<u32>> = RefCell::new(vec![1, 2, 3])); |
1a4d82fc JJ |
739 | |
740 | FOO.with(|vec| { | |
741 | assert_eq!(vec.borrow().len(), 3); | |
742 | vec.borrow_mut().push(4); | |
743 | assert_eq!(vec.borrow()[3], 4); | |
744 | }); | |
745 | } | |
746 | } |