Line data Source code
1 : use std::{
2 : panic::AssertUnwindSafe,
3 : sync::{
4 : atomic::{AtomicBool, AtomicU32, AtomicU8, Ordering},
5 : mpsc, Arc, OnceLock,
6 : },
7 : thread::JoinHandle,
8 : };
9 :
10 : use tracing::{debug, error, trace};
11 :
12 : use crate::time::Timing;
13 :
14 : /// Stores status of the running threads. Threads are registered in the runtime upon creation
15 : /// and deregistered upon termination.
16 : pub struct Runtime {
17 : // stores handles to all threads that are currently running
18 : threads: Vec<ThreadHandle>,
19 : // stores current time and pending wakeups
20 : clock: Arc<Timing>,
21 : // thread counter
22 : thread_counter: AtomicU32,
23 : // Thread step counter -- how many times all threads has been actually
24 : // stepped (note that all world/time/executor/thread have slightly different
25 : // meaning of steps). For observability.
26 : pub step_counter: u64,
27 : }
28 :
29 : impl Runtime {
30 : /// Init new runtime, no running threads.
31 528 : pub fn new(clock: Arc<Timing>) -> Self {
32 528 : Self {
33 528 : threads: Vec::new(),
34 528 : clock,
35 528 : thread_counter: AtomicU32::new(0),
36 528 : step_counter: 0,
37 528 : }
38 528 : }
39 :
40 : /// Spawn a new thread and register it in the runtime.
41 20484 : pub fn spawn<F>(&mut self, f: F) -> ExternalHandle
42 20484 : where
43 20484 : F: FnOnce() + Send + 'static,
44 20484 : {
45 20484 : let (tx, rx) = mpsc::channel();
46 20484 :
47 20484 : let clock = self.clock.clone();
48 20484 : let tid = self.thread_counter.fetch_add(1, Ordering::SeqCst);
49 20484 : debug!("spawning thread-{}", tid);
50 :
51 20484 : let join = std::thread::spawn(move || {
52 20484 : let _guard = tracing::info_span!("", tid).entered();
53 20484 :
54 20484 : let res = std::panic::catch_unwind(AssertUnwindSafe(|| {
55 20484 : with_thread_context(|ctx| {
56 20484 : assert!(ctx.clock.set(clock).is_ok());
57 20484 : ctx.id.store(tid, Ordering::SeqCst);
58 20484 : tx.send(ctx.clone()).expect("failed to send thread context");
59 20484 : // suspend thread to put it to `threads` in sleeping state
60 20484 : ctx.yield_me(0);
61 20484 : });
62 20484 :
63 20484 : // start user-provided function
64 20484 : f();
65 20484 : }));
66 20484 : debug!("thread finished");
67 :
68 20426 : if let Err(e) = res {
69 20406 : with_thread_context(|ctx| {
70 20406 : if !ctx.allow_panic.load(std::sync::atomic::Ordering::SeqCst) {
71 0 : error!("thread panicked, terminating the process: {:?}", e);
72 0 : std::process::exit(1);
73 20406 : }
74 20406 :
75 20406 : debug!("thread panicked: {:?}", e);
76 20406 : let mut result = ctx.result.lock();
77 20406 : if result.0 == -1 {
78 19990 : *result = (256, format!("thread panicked: {:?}", e));
79 19990 : }
80 20406 : });
81 20406 : }
82 :
83 20426 : with_thread_context(|ctx| {
84 20426 : ctx.finish_me();
85 20426 : });
86 20484 : });
87 20484 :
88 20484 : let ctx = rx.recv().expect("failed to receive thread context");
89 20484 : let handle = ThreadHandle::new(ctx.clone(), join);
90 20484 :
91 20484 : self.threads.push(handle);
92 20484 :
93 20484 : ExternalHandle { ctx }
94 20484 : }
95 :
96 : /// Returns true if there are any unfinished activity, such as running thread or pending events.
97 : /// Otherwise returns false, which means all threads are blocked forever.
98 428671 : pub fn step(&mut self) -> bool {
99 428671 : trace!("runtime step");
100 :
101 : // have we run any thread?
102 428671 : let mut ran = false;
103 428671 :
104 2140220 : self.threads.retain(|thread: &ThreadHandle| {
105 2140220 : let res = thread.ctx.wakeup.compare_exchange(
106 2140220 : PENDING_WAKEUP,
107 2140220 : NO_WAKEUP,
108 2140220 : Ordering::SeqCst,
109 2140220 : Ordering::SeqCst,
110 2140220 : );
111 2140220 : if res.is_err() {
112 : // thread has no pending wakeups, leaving as is
113 1844805 : return true;
114 295415 : }
115 295415 : ran = true;
116 295415 :
117 295415 : trace!("entering thread-{}", thread.ctx.tid());
118 295415 : let status = thread.step();
119 295415 : self.step_counter += 1;
120 295415 : trace!(
121 0 : "out of thread-{} with status {:?}",
122 0 : thread.ctx.tid(),
123 : status
124 : );
125 :
126 295415 : if status == Status::Sleep {
127 274989 : true
128 : } else {
129 20426 : trace!("thread has finished");
130 : // removing the thread from the list
131 20426 : false
132 : }
133 2140220 : });
134 428671 :
135 428671 : if !ran {
136 226528 : trace!("no threads were run, stepping clock");
137 226528 : if let Some(ctx_to_wake) = self.clock.step() {
138 225980 : trace!("waking up thread-{}", ctx_to_wake.tid());
139 225980 : ctx_to_wake.inc_wake();
140 : } else {
141 548 : return false;
142 : }
143 202143 : }
144 :
145 428123 : true
146 428671 : }
147 :
148 : /// Kill all threads. This is done by setting a flag in each thread context and waking it up.
149 1008 : pub fn crash_all_threads(&mut self) {
150 2872 : for thread in self.threads.iter() {
151 2872 : thread.ctx.crash_stop();
152 2872 : }
153 :
154 : // all threads should be finished after a few steps
155 1512 : while !self.threads.is_empty() {
156 504 : self.step();
157 504 : }
158 1008 : }
159 : }
160 :
161 : impl Drop for Runtime {
162 503 : fn drop(&mut self) {
163 503 : debug!("dropping the runtime");
164 503 : self.crash_all_threads();
165 503 : }
166 : }
167 :
168 : #[derive(Clone)]
169 : pub struct ExternalHandle {
170 : ctx: Arc<ThreadContext>,
171 : }
172 :
173 : impl ExternalHandle {
174 : /// Returns true if thread has finished execution.
175 444022 : pub fn is_finished(&self) -> bool {
176 444022 : let status = self.ctx.mutex.lock();
177 444022 : *status == Status::Finished
178 444022 : }
179 :
180 : /// Returns exitcode and message, which is available after thread has finished execution.
181 407 : pub fn result(&self) -> (i32, String) {
182 407 : let result = self.ctx.result.lock();
183 407 : result.clone()
184 407 : }
185 :
186 : /// Returns thread id.
187 14 : pub fn id(&self) -> u32 {
188 14 : self.ctx.id.load(Ordering::SeqCst)
189 14 : }
190 :
191 : /// Sets a flag to crash thread on the next wakeup.
192 17479 : pub fn crash_stop(&self) {
193 17479 : self.ctx.crash_stop();
194 17479 : }
195 : }
196 :
197 : struct ThreadHandle {
198 : ctx: Arc<ThreadContext>,
199 : _join: JoinHandle<()>,
200 : }
201 :
202 : impl ThreadHandle {
203 : /// Create a new [`ThreadHandle`] and wait until thread will enter [`Status::Sleep`] state.
204 20484 : fn new(ctx: Arc<ThreadContext>, join: JoinHandle<()>) -> Self {
205 20484 : let mut status = ctx.mutex.lock();
206 : // wait until thread will go into the first yield
207 20527 : while *status != Status::Sleep {
208 43 : ctx.condvar.wait(&mut status);
209 43 : }
210 20484 : drop(status);
211 20484 :
212 20484 : Self { ctx, _join: join }
213 20484 : }
214 :
215 : /// Allows thread to execute one step of its execution.
216 : /// Returns [`Status`] of the thread after the step.
217 295415 : fn step(&self) -> Status {
218 295415 : let mut status = self.ctx.mutex.lock();
219 295415 : assert!(matches!(*status, Status::Sleep));
220 :
221 295415 : *status = Status::Running;
222 295415 : self.ctx.condvar.notify_all();
223 :
224 590830 : while *status == Status::Running {
225 295415 : self.ctx.condvar.wait(&mut status);
226 295415 : }
227 :
228 295415 : *status
229 295415 : }
230 : }
231 :
232 : #[derive(Clone, Copy, Debug, PartialEq, Eq)]
233 : enum Status {
234 : /// Thread is running.
235 : Running,
236 : /// Waiting for event to complete, will be resumed by the executor step, once wakeup flag is set.
237 : Sleep,
238 : /// Thread finished execution.
239 : Finished,
240 : }
241 :
242 : const NO_WAKEUP: u8 = 0;
243 : const PENDING_WAKEUP: u8 = 1;
244 :
245 : pub struct ThreadContext {
246 : id: AtomicU32,
247 : // used to block thread until it is woken up
248 : mutex: parking_lot::Mutex<Status>,
249 : condvar: parking_lot::Condvar,
250 : // used as a flag to indicate runtime that thread is ready to be woken up
251 : wakeup: AtomicU8,
252 : clock: OnceLock<Arc<Timing>>,
253 : // execution result, set by exit() call
254 : result: parking_lot::Mutex<(i32, String)>,
255 : // determines if process should be killed on receiving panic
256 : allow_panic: AtomicBool,
257 : // acts as a signal that thread should crash itself on the next wakeup
258 : crash_request: AtomicBool,
259 : }
260 :
261 : impl ThreadContext {
262 21012 : pub(crate) fn new() -> Self {
263 21012 : Self {
264 21012 : id: AtomicU32::new(0),
265 21012 : mutex: parking_lot::Mutex::new(Status::Running),
266 21012 : condvar: parking_lot::Condvar::new(),
267 21012 : wakeup: AtomicU8::new(NO_WAKEUP),
268 21012 : clock: OnceLock::new(),
269 21012 : result: parking_lot::Mutex::new((-1, String::new())),
270 21012 : allow_panic: AtomicBool::new(false),
271 21012 : crash_request: AtomicBool::new(false),
272 21012 : }
273 21012 : }
274 : }
275 :
276 : // Functions for executor to control thread execution.
277 : impl ThreadContext {
278 : /// Set atomic flag to indicate that thread is ready to be woken up.
279 711598 : fn inc_wake(&self) {
280 711598 : self.wakeup.store(PENDING_WAKEUP, Ordering::SeqCst);
281 711598 : }
282 :
283 : /// Internal function used for event queues.
284 185489 : pub(crate) fn schedule_wakeup(self: &Arc<Self>, after_ms: u64) {
285 185489 : self.clock
286 185489 : .get()
287 185489 : .unwrap()
288 185489 : .schedule_wakeup(after_ms, self.clone());
289 185489 : }
290 :
291 1 : fn tid(&self) -> u32 {
292 1 : self.id.load(Ordering::SeqCst)
293 1 : }
294 :
295 20351 : fn crash_stop(&self) {
296 20351 : let status = self.mutex.lock();
297 20351 : if *status == Status::Finished {
298 9 : debug!(
299 0 : "trying to crash thread-{}, which is already finished",
300 0 : self.tid()
301 : );
302 9 : return;
303 20342 : }
304 20342 : assert!(matches!(*status, Status::Sleep));
305 20342 : drop(status);
306 20342 :
307 20342 : self.allow_panic.store(true, Ordering::SeqCst);
308 20342 : self.crash_request.store(true, Ordering::SeqCst);
309 20342 : // set a wakeup
310 20342 : self.inc_wake();
311 : // it will panic on the next wakeup
312 20351 : }
313 : }
314 :
315 : // Internal functions.
316 : impl ThreadContext {
317 : /// Blocks thread until it's woken up by the executor. If `after_ms` is 0, is will be
318 : /// woken on the next step. If `after_ms` > 0, wakeup is scheduled after that time.
319 : /// Otherwise wakeup is not scheduled inside `yield_me`, and should be arranged before
320 : /// calling this function.
321 295473 : fn yield_me(self: &Arc<Self>, after_ms: i64) {
322 295473 : let mut status = self.mutex.lock();
323 295473 : assert!(matches!(*status, Status::Running));
324 :
325 295473 : match after_ms.cmp(&0) {
326 244564 : std::cmp::Ordering::Less => {
327 244564 : // block until something wakes us up
328 244564 : }
329 22012 : std::cmp::Ordering::Equal => {
330 22012 : // tell executor that we are ready to be woken up
331 22012 : self.inc_wake();
332 22012 : }
333 28897 : std::cmp::Ordering::Greater => {
334 28897 : // schedule wakeup
335 28897 : self.clock
336 28897 : .get()
337 28897 : .unwrap()
338 28897 : .schedule_wakeup(after_ms as u64, self.clone());
339 28897 : }
340 : }
341 :
342 295473 : *status = Status::Sleep;
343 295473 : self.condvar.notify_all();
344 :
345 : // wait until executor wakes us up
346 590946 : while *status != Status::Running {
347 295473 : self.condvar.wait(&mut status);
348 295473 : }
349 :
350 295473 : if self.crash_request.load(Ordering::SeqCst) {
351 19990 : panic!("crashed by request");
352 275483 : }
353 275483 : }
354 :
355 : /// Called only once, exactly before thread finishes execution.
356 20426 : fn finish_me(&self) {
357 20426 : let mut status = self.mutex.lock();
358 20426 : assert!(matches!(*status, Status::Running));
359 :
360 20426 : *status = Status::Finished;
361 20426 : {
362 20426 : let mut result = self.result.lock();
363 20426 : if result.0 == -1 {
364 20 : *result = (0, "finished normally".to_owned());
365 20406 : }
366 : }
367 20426 : self.condvar.notify_all();
368 20426 : }
369 : }
370 :
371 : /// Invokes the given closure with a reference to the current thread [`ThreadContext`].
372 : #[inline(always)]
373 1946547 : fn with_thread_context<T>(f: impl FnOnce(&Arc<ThreadContext>) -> T) -> T {
374 1946547 : thread_local!(static THREAD_DATA: Arc<ThreadContext> = Arc::new(ThreadContext::new()));
375 1946547 : THREAD_DATA.with(f)
376 1946547 : }
377 :
378 : /// Waker is used to wake up threads that are blocked on condition.
379 : /// It keeps track of contexts [`Arc<ThreadContext>`] and can increment the counter
380 : /// of several contexts to send a notification.
381 : pub struct Waker {
382 : // contexts that are waiting for a notification
383 : contexts: parking_lot::Mutex<smallvec::SmallVec<[Arc<ThreadContext>; 8]>>,
384 : }
385 :
386 : impl Default for Waker {
387 0 : fn default() -> Self {
388 0 : Self::new()
389 0 : }
390 : }
391 :
392 : impl Waker {
393 83931 : pub fn new() -> Self {
394 83931 : Self {
395 83931 : contexts: parking_lot::Mutex::new(smallvec::SmallVec::new()),
396 83931 : }
397 83931 : }
398 :
399 : /// Subscribe current thread to receive a wake notification later.
400 872196 : pub fn wake_me_later(&self) {
401 872196 : with_thread_context(|ctx| {
402 872196 : self.contexts.lock().push(ctx.clone());
403 872196 : });
404 872196 : }
405 :
406 : /// Wake up all threads that are waiting for a notification and clear the list.
407 128814 : pub fn wake_all(&self) {
408 128814 : let mut v = self.contexts.lock();
409 443264 : for ctx in v.iter() {
410 443264 : ctx.inc_wake();
411 443264 : }
412 128814 : v.clear();
413 128814 : }
414 : }
415 :
416 : /// See [`ThreadContext::yield_me`].
417 274989 : pub fn yield_me(after_ms: i64) {
418 274989 : with_thread_context(|ctx| ctx.yield_me(after_ms))
419 274989 : }
420 :
421 : /// Get current time.
422 737102 : pub fn now() -> u64 {
423 737102 : with_thread_context(|ctx| ctx.clock.get().unwrap().now())
424 737102 : }
425 :
426 416 : pub fn exit(code: i32, msg: String) {
427 416 : with_thread_context(|ctx| {
428 416 : ctx.allow_panic.store(true, Ordering::SeqCst);
429 416 : let mut result = ctx.result.lock();
430 416 : *result = (code, msg);
431 416 : panic!("exit");
432 416 : });
433 416 : }
434 :
435 528 : pub(crate) fn get_thread_ctx() -> Arc<ThreadContext> {
436 528 : with_thread_context(|ctx| ctx.clone())
437 528 : }
438 :
439 : /// Trait for polling channels until they have something.
440 : pub trait PollSome {
441 : /// Schedule wakeup for message arrival.
442 : fn wake_me(&self);
443 :
444 : /// Check if channel has a ready message.
445 : fn has_some(&self) -> bool;
446 : }
447 :
448 : /// Blocks current thread until one of the channels has a ready message. Returns
449 : /// index of the channel that has a message. If timeout is reached, returns None.
450 : ///
451 : /// Negative timeout means block forever. Zero timeout means check channels and return
452 : /// immediately. Positive timeout means block until timeout is reached.
453 109519 : pub fn epoll_chans(chans: &[Box<dyn PollSome>], timeout: i64) -> Option<usize> {
454 109519 : let deadline = if timeout < 0 {
455 79878 : 0
456 : } else {
457 29641 : now() + timeout as u64
458 : };
459 :
460 : loop {
461 1076671 : for chan in chans {
462 869368 : chan.wake_me()
463 : }
464 :
465 699466 : for (i, chan) in chans.iter().enumerate() {
466 699466 : if chan.has_some() {
467 87556 : return Some(i);
468 611910 : }
469 : }
470 :
471 100649 : if timeout < 0 {
472 68887 : // block until wakeup
473 68887 : yield_me(-1);
474 68887 : } else {
475 31762 : let current_time = now();
476 31762 : if current_time >= deadline {
477 2865 : return None;
478 28897 : }
479 28897 :
480 28897 : yield_me((deadline - current_time) as i64);
481 : }
482 : }
483 90421 : }
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