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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087
//! Implements threads.
use std::cell::RefCell;
use std::collections::hash_map::Entry;
use std::num::TryFromIntError;
use std::sync::atomic::{AtomicBool, Ordering::Relaxed};
use std::task::Poll;
use std::time::{Duration, SystemTime};
use either::Either;
use log::trace;
use rustc_data_structures::fx::FxHashMap;
use rustc_hir::def_id::DefId;
use rustc_index::{Idx, IndexVec};
use rustc_middle::mir::Mutability;
use rustc_middle::ty::layout::TyAndLayout;
use rustc_span::Span;
use rustc_target::spec::abi::Abi;
use crate::concurrency::data_race;
use crate::concurrency::sync::SynchronizationState;
use crate::shims::tls;
use crate::*;
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
enum SchedulingAction {
/// Execute step on the active thread.
ExecuteStep,
/// Execute a timeout callback.
ExecuteTimeoutCallback,
/// Wait for a bit, until there is a timeout to be called.
Sleep(Duration),
}
/// Trait for callbacks that can be executed when some event happens, such as after a timeout.
pub trait MachineCallback<'mir, 'tcx>: VisitTags {
fn call(&self, ecx: &mut InterpCx<'mir, 'tcx, MiriMachine<'mir, 'tcx>>) -> InterpResult<'tcx>;
}
type TimeoutCallback<'mir, 'tcx> = Box<dyn MachineCallback<'mir, 'tcx> + 'tcx>;
/// A thread identifier.
#[derive(Clone, Copy, Debug, PartialOrd, Ord, PartialEq, Eq, Hash)]
pub struct ThreadId(u32);
impl ThreadId {
pub fn to_u32(self) -> u32 {
self.0
}
}
impl Idx for ThreadId {
fn new(idx: usize) -> Self {
ThreadId(u32::try_from(idx).unwrap())
}
fn index(self) -> usize {
usize::try_from(self.0).unwrap()
}
}
impl TryFrom<u64> for ThreadId {
type Error = TryFromIntError;
fn try_from(id: u64) -> Result<Self, Self::Error> {
u32::try_from(id).map(Self)
}
}
impl From<u32> for ThreadId {
fn from(id: u32) -> Self {
Self(id)
}
}
impl From<ThreadId> for u64 {
fn from(t: ThreadId) -> Self {
t.0.into()
}
}
/// The state of a thread.
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
pub enum ThreadState {
/// The thread is enabled and can be executed.
Enabled,
/// The thread tried to join the specified thread and is blocked until that
/// thread terminates.
BlockedOnJoin(ThreadId),
/// The thread is blocked on some synchronization primitive. It is the
/// responsibility of the synchronization primitives to track threads that
/// are blocked by them.
BlockedOnSync,
/// The thread has terminated its execution. We do not delete terminated
/// threads (FIXME: why?).
Terminated,
}
/// The join status of a thread.
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
enum ThreadJoinStatus {
/// The thread can be joined.
Joinable,
/// A thread is detached if its join handle was destroyed and no other
/// thread can join it.
Detached,
/// The thread was already joined by some thread and cannot be joined again.
Joined,
}
/// A thread.
pub struct Thread<'mir, 'tcx> {
state: ThreadState,
/// Name of the thread.
thread_name: Option<Vec<u8>>,
/// The virtual call stack.
stack: Vec<Frame<'mir, 'tcx, Provenance, FrameExtra<'tcx>>>,
/// The function to call when the stack ran empty, to figure out what to do next.
/// Conceptually, this is the interpreter implementation of the things that happen 'after' the
/// Rust language entry point for this thread returns (usually implemented by the C or OS runtime).
/// (`None` is an error, it means the callback has not been set up yet or is actively running.)
pub(crate) on_stack_empty: Option<StackEmptyCallback<'mir, 'tcx>>,
/// The index of the topmost user-relevant frame in `stack`. This field must contain
/// the value produced by `get_top_user_relevant_frame`.
/// The `None` state here represents
/// This field is a cache to reduce how often we call that method. The cache is manually
/// maintained inside `MiriMachine::after_stack_push` and `MiriMachine::after_stack_pop`.
top_user_relevant_frame: Option<usize>,
/// The join status.
join_status: ThreadJoinStatus,
/// Stack of active panic payloads for the current thread. Used for storing
/// the argument of the call to `miri_start_panic` (the panic payload) when unwinding.
/// This is pointer-sized, and matches the `Payload` type in `src/libpanic_unwind/miri.rs`.
///
/// In real unwinding, the payload gets passed as an argument to the landing pad,
/// which then forwards it to 'Resume'. However this argument is implicit in MIR,
/// so we have to store it out-of-band. When there are multiple active unwinds,
/// the innermost one is always caught first, so we can store them as a stack.
pub(crate) panic_payloads: Vec<Scalar<Provenance>>,
/// Last OS error location in memory. It is a 32-bit integer.
pub(crate) last_error: Option<MPlaceTy<'tcx, Provenance>>,
}
pub type StackEmptyCallback<'mir, 'tcx> =
Box<dyn FnMut(&mut MiriInterpCx<'mir, 'tcx>) -> InterpResult<'tcx, Poll<()>>>;
impl<'mir, 'tcx> Thread<'mir, 'tcx> {
/// Get the name of the current thread, or `<unnamed>` if it was not set.
fn thread_name(&self) -> &[u8] {
if let Some(ref thread_name) = self.thread_name { thread_name } else { b"<unnamed>" }
}
/// Return the top user-relevant frame, if there is one.
/// Note that the choice to return `None` here when there is no user-relevant frame is part of
/// justifying the optimization that only pushes of user-relevant frames require updating the
/// `top_user_relevant_frame` field.
fn compute_top_user_relevant_frame(&self) -> Option<usize> {
self.stack
.iter()
.enumerate()
.rev()
.find_map(|(idx, frame)| if frame.extra.is_user_relevant { Some(idx) } else { None })
}
/// Re-compute the top user-relevant frame from scratch.
pub fn recompute_top_user_relevant_frame(&mut self) {
self.top_user_relevant_frame = self.compute_top_user_relevant_frame();
}
/// Set the top user-relevant frame to the given value. Must be equal to what
/// `get_top_user_relevant_frame` would return!
pub fn set_top_user_relevant_frame(&mut self, frame_idx: usize) {
debug_assert_eq!(Some(frame_idx), self.compute_top_user_relevant_frame());
self.top_user_relevant_frame = Some(frame_idx);
}
/// Returns the topmost frame that is considered user-relevant, or the
/// top of the stack if there is no such frame, or `None` if the stack is empty.
pub fn top_user_relevant_frame(&self) -> Option<usize> {
debug_assert_eq!(self.top_user_relevant_frame, self.compute_top_user_relevant_frame());
// This can be called upon creation of an allocation. We create allocations while setting up
// parts of the Rust runtime when we do not have any stack frames yet, so we need to handle
// empty stacks.
self.top_user_relevant_frame.or_else(|| self.stack.len().checked_sub(1))
}
}
impl<'mir, 'tcx> std::fmt::Debug for Thread<'mir, 'tcx> {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
write!(
f,
"{}({:?}, {:?})",
String::from_utf8_lossy(self.thread_name()),
self.state,
self.join_status
)
}
}
impl<'mir, 'tcx> Thread<'mir, 'tcx> {
fn new(name: Option<&str>, on_stack_empty: Option<StackEmptyCallback<'mir, 'tcx>>) -> Self {
Self {
state: ThreadState::Enabled,
thread_name: name.map(|name| Vec::from(name.as_bytes())),
stack: Vec::new(),
top_user_relevant_frame: None,
join_status: ThreadJoinStatus::Joinable,
panic_payloads: Vec::new(),
last_error: None,
on_stack_empty,
}
}
}
impl VisitTags for Thread<'_, '_> {
fn visit_tags(&self, visit: &mut dyn FnMut(BorTag)) {
let Thread {
panic_payloads: panic_payload,
last_error,
stack,
top_user_relevant_frame: _,
state: _,
thread_name: _,
join_status: _,
on_stack_empty: _, // we assume the closure captures no GC-relevant state
} = self;
for payload in panic_payload {
payload.visit_tags(visit);
}
last_error.visit_tags(visit);
for frame in stack {
frame.visit_tags(visit)
}
}
}
impl VisitTags for Frame<'_, '_, Provenance, FrameExtra<'_>> {
fn visit_tags(&self, visit: &mut dyn FnMut(BorTag)) {
let Frame {
return_place,
locals,
extra,
body: _,
instance: _,
return_to_block: _,
loc: _,
// There are some private fields we cannot access; they contain no tags.
..
} = self;
// Return place.
return_place.visit_tags(visit);
// Locals.
for local in locals.iter() {
match local.as_mplace_or_imm() {
None => {}
Some(Either::Left((ptr, meta))) => {
ptr.visit_tags(visit);
meta.visit_tags(visit);
}
Some(Either::Right(imm)) => {
imm.visit_tags(visit);
}
}
}
extra.visit_tags(visit);
}
}
/// A specific moment in time.
#[derive(Debug)]
pub enum Time {
Monotonic(Instant),
RealTime(SystemTime),
}
impl Time {
/// How long do we have to wait from now until the specified time?
fn get_wait_time(&self, clock: &Clock) -> Duration {
match self {
Time::Monotonic(instant) => instant.duration_since(clock.now()),
Time::RealTime(time) =>
time.duration_since(SystemTime::now()).unwrap_or(Duration::new(0, 0)),
}
}
}
/// Callbacks are used to implement timeouts. For example, waiting on a
/// conditional variable with a timeout creates a callback that is called after
/// the specified time and unblocks the thread. If another thread signals on the
/// conditional variable, the signal handler deletes the callback.
struct TimeoutCallbackInfo<'mir, 'tcx> {
/// The callback should be called no earlier than this time.
call_time: Time,
/// The called function.
callback: TimeoutCallback<'mir, 'tcx>,
}
impl<'mir, 'tcx> std::fmt::Debug for TimeoutCallbackInfo<'mir, 'tcx> {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
write!(f, "TimeoutCallback({:?})", self.call_time)
}
}
/// A set of threads.
#[derive(Debug)]
pub struct ThreadManager<'mir, 'tcx> {
/// Identifier of the currently active thread.
active_thread: ThreadId,
/// Threads used in the program.
///
/// Note that this vector also contains terminated threads.
threads: IndexVec<ThreadId, Thread<'mir, 'tcx>>,
/// This field is pub(crate) because the synchronization primitives
/// (`crate::sync`) need a way to access it.
pub(crate) sync: SynchronizationState<'mir, 'tcx>,
/// A mapping from a thread-local static to an allocation id of a thread
/// specific allocation.
thread_local_alloc_ids: RefCell<FxHashMap<(DefId, ThreadId), Pointer<Provenance>>>,
/// A flag that indicates that we should change the active thread.
yield_active_thread: bool,
/// Callbacks that are called once the specified time passes.
timeout_callbacks: FxHashMap<ThreadId, TimeoutCallbackInfo<'mir, 'tcx>>,
}
impl VisitTags for ThreadManager<'_, '_> {
fn visit_tags(&self, visit: &mut dyn FnMut(BorTag)) {
let ThreadManager {
threads,
thread_local_alloc_ids,
timeout_callbacks,
active_thread: _,
yield_active_thread: _,
sync,
} = self;
for thread in threads {
thread.visit_tags(visit);
}
for ptr in thread_local_alloc_ids.borrow().values() {
ptr.visit_tags(visit);
}
for callback in timeout_callbacks.values() {
callback.callback.visit_tags(visit);
}
sync.visit_tags(visit);
}
}
impl<'mir, 'tcx> Default for ThreadManager<'mir, 'tcx> {
fn default() -> Self {
let mut threads = IndexVec::new();
// Create the main thread and add it to the list of threads.
threads.push(Thread::new(Some("main"), None));
Self {
active_thread: ThreadId::new(0),
threads,
sync: SynchronizationState::default(),
thread_local_alloc_ids: Default::default(),
yield_active_thread: false,
timeout_callbacks: FxHashMap::default(),
}
}
}
impl<'mir, 'tcx: 'mir> ThreadManager<'mir, 'tcx> {
pub(crate) fn init(
ecx: &mut MiriInterpCx<'mir, 'tcx>,
on_main_stack_empty: StackEmptyCallback<'mir, 'tcx>,
) {
ecx.machine.threads.threads[ThreadId::new(0)].on_stack_empty = Some(on_main_stack_empty);
if ecx.tcx.sess.target.os.as_ref() != "windows" {
// The main thread can *not* be joined on except on windows.
ecx.machine.threads.threads[ThreadId::new(0)].join_status = ThreadJoinStatus::Detached;
}
}
/// Check if we have an allocation for the given thread local static for the
/// active thread.
fn get_thread_local_alloc_id(&self, def_id: DefId) -> Option<Pointer<Provenance>> {
self.thread_local_alloc_ids.borrow().get(&(def_id, self.active_thread)).cloned()
}
/// Set the pointer for the allocation of the given thread local
/// static for the active thread.
///
/// Panics if a thread local is initialized twice for the same thread.
fn set_thread_local_alloc(&self, def_id: DefId, ptr: Pointer<Provenance>) {
self.thread_local_alloc_ids
.borrow_mut()
.try_insert((def_id, self.active_thread), ptr)
.unwrap();
}
/// Borrow the stack of the active thread.
pub fn active_thread_stack(&self) -> &[Frame<'mir, 'tcx, Provenance, FrameExtra<'tcx>>] {
&self.threads[self.active_thread].stack
}
/// Mutably borrow the stack of the active thread.
fn active_thread_stack_mut(
&mut self,
) -> &mut Vec<Frame<'mir, 'tcx, Provenance, FrameExtra<'tcx>>> {
&mut self.threads[self.active_thread].stack
}
pub fn all_stacks(
&self,
) -> impl Iterator<Item = &[Frame<'mir, 'tcx, Provenance, FrameExtra<'tcx>>]> {
self.threads.iter().map(|t| &t.stack[..])
}
/// Create a new thread and returns its id.
fn create_thread(&mut self, on_stack_empty: StackEmptyCallback<'mir, 'tcx>) -> ThreadId {
let new_thread_id = ThreadId::new(self.threads.len());
self.threads.push(Thread::new(None, Some(on_stack_empty)));
new_thread_id
}
/// Set an active thread and return the id of the thread that was active before.
fn set_active_thread_id(&mut self, id: ThreadId) -> ThreadId {
let active_thread_id = self.active_thread;
self.active_thread = id;
assert!(self.active_thread.index() < self.threads.len());
active_thread_id
}
/// Get the id of the currently active thread.
pub fn get_active_thread_id(&self) -> ThreadId {
self.active_thread
}
/// Get the total number of threads that were ever spawn by this program.
pub fn get_total_thread_count(&self) -> usize {
self.threads.len()
}
/// Get the total of threads that are currently live, i.e., not yet terminated.
/// (They might be blocked.)
pub fn get_live_thread_count(&self) -> usize {
self.threads.iter().filter(|t| !matches!(t.state, ThreadState::Terminated)).count()
}
/// Has the given thread terminated?
fn has_terminated(&self, thread_id: ThreadId) -> bool {
self.threads[thread_id].state == ThreadState::Terminated
}
/// Have all threads terminated?
fn have_all_terminated(&self) -> bool {
self.threads.iter().all(|thread| thread.state == ThreadState::Terminated)
}
/// Enable the thread for execution. The thread must be terminated.
fn enable_thread(&mut self, thread_id: ThreadId) {
assert!(self.has_terminated(thread_id));
self.threads[thread_id].state = ThreadState::Enabled;
}
/// Get a mutable borrow of the currently active thread.
pub fn active_thread_mut(&mut self) -> &mut Thread<'mir, 'tcx> {
&mut self.threads[self.active_thread]
}
/// Get a shared borrow of the currently active thread.
pub fn active_thread_ref(&self) -> &Thread<'mir, 'tcx> {
&self.threads[self.active_thread]
}
/// Mark the thread as detached, which means that no other thread will try
/// to join it and the thread is responsible for cleaning up.
///
/// `allow_terminated_joined` allows detaching joined threads that have already terminated.
/// This matches Windows's behavior for `CloseHandle`.
///
/// See <https://docs.microsoft.com/en-us/windows/win32/procthread/thread-handles-and-identifiers>:
/// > The handle is valid until closed, even after the thread it represents has been terminated.
fn detach_thread(&mut self, id: ThreadId, allow_terminated_joined: bool) -> InterpResult<'tcx> {
trace!("detaching {:?}", id);
let is_ub = if allow_terminated_joined && self.threads[id].state == ThreadState::Terminated
{
// "Detached" in particular means "not yet joined". Redundant detaching is still UB.
self.threads[id].join_status == ThreadJoinStatus::Detached
} else {
self.threads[id].join_status != ThreadJoinStatus::Joinable
};
if is_ub {
throw_ub_format!("trying to detach thread that was already detached or joined");
}
self.threads[id].join_status = ThreadJoinStatus::Detached;
Ok(())
}
/// Mark that the active thread tries to join the thread with `joined_thread_id`.
fn join_thread(
&mut self,
joined_thread_id: ThreadId,
data_race: Option<&mut data_race::GlobalState>,
) -> InterpResult<'tcx> {
if self.threads[joined_thread_id].join_status == ThreadJoinStatus::Detached {
// On Windows this corresponds to joining on a closed handle.
throw_ub_format!("trying to join a detached thread");
}
// Mark the joined thread as being joined so that we detect if other
// threads try to join it.
self.threads[joined_thread_id].join_status = ThreadJoinStatus::Joined;
if self.threads[joined_thread_id].state != ThreadState::Terminated {
// The joined thread is still running, we need to wait for it.
self.active_thread_mut().state = ThreadState::BlockedOnJoin(joined_thread_id);
trace!(
"{:?} blocked on {:?} when trying to join",
self.active_thread,
joined_thread_id
);
} else {
// The thread has already terminated - mark join happens-before
if let Some(data_race) = data_race {
data_race.thread_joined(self, self.active_thread, joined_thread_id);
}
}
Ok(())
}
/// Mark that the active thread tries to exclusively join the thread with `joined_thread_id`.
/// If the thread is already joined by another thread, it will throw UB
fn join_thread_exclusive(
&mut self,
joined_thread_id: ThreadId,
data_race: Option<&mut data_race::GlobalState>,
) -> InterpResult<'tcx> {
if self.threads[joined_thread_id].join_status == ThreadJoinStatus::Joined {
throw_ub_format!("trying to join an already joined thread");
}
if joined_thread_id == self.active_thread {
throw_ub_format!("trying to join itself");
}
assert!(
self.threads
.iter()
.all(|thread| thread.state != ThreadState::BlockedOnJoin(joined_thread_id)),
"this thread already has threads waiting for its termination"
);
self.join_thread(joined_thread_id, data_race)
}
/// Set the name of the given thread.
pub fn set_thread_name(&mut self, thread: ThreadId, new_thread_name: Vec<u8>) {
self.threads[thread].thread_name = Some(new_thread_name);
}
/// Get the name of the given thread.
pub fn get_thread_name(&self, thread: ThreadId) -> &[u8] {
self.threads[thread].thread_name()
}
/// Put the thread into the blocked state.
fn block_thread(&mut self, thread: ThreadId) {
let state = &mut self.threads[thread].state;
assert_eq!(*state, ThreadState::Enabled);
*state = ThreadState::BlockedOnSync;
}
/// Put the blocked thread into the enabled state.
fn unblock_thread(&mut self, thread: ThreadId) {
let state = &mut self.threads[thread].state;
assert_eq!(*state, ThreadState::BlockedOnSync);
*state = ThreadState::Enabled;
}
/// Change the active thread to some enabled thread.
fn yield_active_thread(&mut self) {
// We do not yield immediately, as swapping out the current stack while executing a MIR statement
// could lead to all sorts of confusion.
// We should only switch stacks between steps.
self.yield_active_thread = true;
}
/// Register the given `callback` to be called once the `call_time` passes.
///
/// The callback will be called with `thread` being the active thread, and
/// the callback may not change the active thread.
fn register_timeout_callback(
&mut self,
thread: ThreadId,
call_time: Time,
callback: TimeoutCallback<'mir, 'tcx>,
) {
self.timeout_callbacks
.try_insert(thread, TimeoutCallbackInfo { call_time, callback })
.unwrap();
}
/// Unregister the callback for the `thread`.
fn unregister_timeout_callback_if_exists(&mut self, thread: ThreadId) {
self.timeout_callbacks.remove(&thread);
}
/// Get a callback that is ready to be called.
fn get_ready_callback(
&mut self,
clock: &Clock,
) -> Option<(ThreadId, TimeoutCallback<'mir, 'tcx>)> {
// We iterate over all threads in the order of their indices because
// this allows us to have a deterministic scheduler.
for thread in self.threads.indices() {
match self.timeout_callbacks.entry(thread) {
Entry::Occupied(entry) => {
if entry.get().call_time.get_wait_time(clock) == Duration::new(0, 0) {
return Some((thread, entry.remove().callback));
}
}
Entry::Vacant(_) => {}
}
}
None
}
/// Wakes up threads joining on the active one and deallocates thread-local statics.
/// The `AllocId` that can now be freed are returned.
fn thread_terminated(
&mut self,
mut data_race: Option<&mut data_race::GlobalState>,
current_span: Span,
) -> Vec<Pointer<Provenance>> {
let mut free_tls_statics = Vec::new();
{
let mut thread_local_statics = self.thread_local_alloc_ids.borrow_mut();
thread_local_statics.retain(|&(_def_id, thread), &mut alloc_id| {
if thread != self.active_thread {
// Keep this static around.
return true;
}
// Delete this static from the map and from memory.
// We cannot free directly here as we cannot use `?` in this context.
free_tls_statics.push(alloc_id);
false
});
}
// Set the thread into a terminated state in the data-race detector.
if let Some(ref mut data_race) = data_race {
data_race.thread_terminated(self, current_span);
}
// Check if we need to unblock any threads.
let mut joined_threads = vec![]; // store which threads joined, we'll need it
for (i, thread) in self.threads.iter_enumerated_mut() {
if thread.state == ThreadState::BlockedOnJoin(self.active_thread) {
// The thread has terminated, mark happens-before edge to joining thread
if data_race.is_some() {
joined_threads.push(i);
}
trace!("unblocking {:?} because {:?} terminated", i, self.active_thread);
thread.state = ThreadState::Enabled;
}
}
for &i in &joined_threads {
data_race.as_mut().unwrap().thread_joined(self, i, self.active_thread);
}
free_tls_statics
}
/// Decide which action to take next and on which thread.
///
/// The currently implemented scheduling policy is the one that is commonly
/// used in stateless model checkers such as Loom: run the active thread as
/// long as we can and switch only when we have to (the active thread was
/// blocked, terminated, or has explicitly asked to be preempted).
fn schedule(&mut self, clock: &Clock) -> InterpResult<'tcx, SchedulingAction> {
// This thread and the program can keep going.
if self.threads[self.active_thread].state == ThreadState::Enabled
&& !self.yield_active_thread
{
// The currently active thread is still enabled, just continue with it.
return Ok(SchedulingAction::ExecuteStep);
}
// The active thread yielded or got terminated. Let's see if there are any timeouts to take
// care of. We do this *before* running any other thread, to ensure that timeouts "in the
// past" fire before any other thread can take an action. This ensures that for
// `pthread_cond_timedwait`, "an error is returned if [...] the absolute time specified by
// abstime has already been passed at the time of the call".
// <https://pubs.opengroup.org/onlinepubs/9699919799/functions/pthread_cond_timedwait.html>
let potential_sleep_time =
self.timeout_callbacks.values().map(|info| info.call_time.get_wait_time(clock)).min();
if potential_sleep_time == Some(Duration::new(0, 0)) {
return Ok(SchedulingAction::ExecuteTimeoutCallback);
}
// No callbacks immediately scheduled, pick a regular thread to execute.
// The active thread blocked or yielded. So we go search for another enabled thread.
// Crucially, we start searching at the current active thread ID, rather than at 0, since we
// want to avoid always scheduling threads 0 and 1 without ever making progress in thread 2.
//
// `skip(N)` means we start iterating at thread N, so we skip 1 more to start just *after*
// the active thread. Then after that we look at `take(N)`, i.e., the threads *before* the
// active thread.
let threads = self
.threads
.iter_enumerated()
.skip(self.active_thread.index() + 1)
.chain(self.threads.iter_enumerated().take(self.active_thread.index()));
for (id, thread) in threads {
debug_assert_ne!(self.active_thread, id);
if thread.state == ThreadState::Enabled {
self.active_thread = id;
break;
}
}
self.yield_active_thread = false;
if self.threads[self.active_thread].state == ThreadState::Enabled {
return Ok(SchedulingAction::ExecuteStep);
}
// We have not found a thread to execute.
if self.threads.iter().all(|thread| thread.state == ThreadState::Terminated) {
unreachable!("all threads terminated without the main thread terminating?!");
} else if let Some(sleep_time) = potential_sleep_time {
// All threads are currently blocked, but we have unexecuted
// timeout_callbacks, which may unblock some of the threads. Hence,
// sleep until the first callback.
Ok(SchedulingAction::Sleep(sleep_time))
} else {
throw_machine_stop!(TerminationInfo::Deadlock);
}
}
}
impl<'mir, 'tcx: 'mir> EvalContextPrivExt<'mir, 'tcx> for MiriInterpCx<'mir, 'tcx> {}
trait EvalContextPrivExt<'mir, 'tcx: 'mir>: MiriInterpCxExt<'mir, 'tcx> {
/// Execute a timeout callback on the callback's thread.
#[inline]
fn run_timeout_callback(&mut self) -> InterpResult<'tcx> {
let this = self.eval_context_mut();
let (thread, callback) = if let Some((thread, callback)) =
this.machine.threads.get_ready_callback(&this.machine.clock)
{
(thread, callback)
} else {
// get_ready_callback can return None if the computer's clock
// was shifted after calling the scheduler and before the call
// to get_ready_callback (see issue
// https://github.com/rust-lang/miri/issues/1763). In this case,
// just do nothing, which effectively just returns to the
// scheduler.
return Ok(());
};
// This back-and-forth with `set_active_thread` is here because of two
// design decisions:
// 1. Make the caller and not the callback responsible for changing
// thread.
// 2. Make the scheduler the only place that can change the active
// thread.
let old_thread = this.set_active_thread(thread);
callback.call(this)?;
this.set_active_thread(old_thread);
Ok(())
}
#[inline]
fn run_on_stack_empty(&mut self) -> InterpResult<'tcx, Poll<()>> {
let this = self.eval_context_mut();
let mut callback = this
.active_thread_mut()
.on_stack_empty
.take()
.expect("`on_stack_empty` not set up, or already running");
let res = callback(this)?;
this.active_thread_mut().on_stack_empty = Some(callback);
Ok(res)
}
}
// Public interface to thread management.
impl<'mir, 'tcx: 'mir> EvalContextExt<'mir, 'tcx> for crate::MiriInterpCx<'mir, 'tcx> {}
pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
/// Get a thread-specific allocation id for the given thread-local static.
/// If needed, allocate a new one.
fn get_or_create_thread_local_alloc(
&mut self,
def_id: DefId,
) -> InterpResult<'tcx, Pointer<Provenance>> {
let this = self.eval_context_mut();
let tcx = this.tcx;
if let Some(old_alloc) = this.machine.threads.get_thread_local_alloc_id(def_id) {
// We already have a thread-specific allocation id for this
// thread-local static.
Ok(old_alloc)
} else {
// We need to allocate a thread-specific allocation id for this
// thread-local static.
// First, we compute the initial value for this static.
if tcx.is_foreign_item(def_id) {
throw_unsup_format!("foreign thread-local statics are not supported");
}
let allocation = this.ctfe_query(|tcx| tcx.eval_static_initializer(def_id))?;
let mut allocation = allocation.inner().clone();
// This allocation will be deallocated when the thread dies, so it is not in read-only memory.
allocation.mutability = Mutability::Mut;
// Create a fresh allocation with this content.
let new_alloc = this.allocate_raw_ptr(allocation, MiriMemoryKind::Tls.into())?;
this.machine.threads.set_thread_local_alloc(def_id, new_alloc);
Ok(new_alloc)
}
}
/// Start a regular (non-main) thread.
#[inline]
fn start_regular_thread(
&mut self,
thread: Option<MPlaceTy<'tcx, Provenance>>,
start_routine: Pointer<Option<Provenance>>,
start_abi: Abi,
func_arg: ImmTy<'tcx, Provenance>,
ret_layout: TyAndLayout<'tcx>,
) -> InterpResult<'tcx, ThreadId> {
let this = self.eval_context_mut();
// Create the new thread
let new_thread_id = this.machine.threads.create_thread({
let mut state = tls::TlsDtorsState::default();
Box::new(move |m| state.on_stack_empty(m))
});
let current_span = this.machine.current_span();
if let Some(data_race) = &mut this.machine.data_race {
data_race.thread_created(&this.machine.threads, new_thread_id, current_span);
}
// Write the current thread-id, switch to the next thread later
// to treat this write operation as occurring on the current thread.
if let Some(thread_info_place) = thread {
this.write_scalar(
Scalar::from_uint(new_thread_id.to_u32(), thread_info_place.layout.size),
&thread_info_place,
)?;
}
// Finally switch to new thread so that we can push the first stackframe.
// After this all accesses will be treated as occurring in the new thread.
let old_thread_id = this.set_active_thread(new_thread_id);
// Perform the function pointer load in the new thread frame.
let instance = this.get_ptr_fn(start_routine)?.as_instance()?;
// Note: the returned value is currently ignored (see the FIXME in
// pthread_join in shims/unix/thread.rs) because the Rust standard library does not use
// it.
let ret_place = this.allocate(ret_layout, MiriMemoryKind::Machine.into())?;
this.call_function(
instance,
start_abi,
&[*func_arg],
Some(&ret_place.into()),
StackPopCleanup::Root { cleanup: true },
)?;
// Restore the old active thread frame.
this.set_active_thread(old_thread_id);
Ok(new_thread_id)
}
#[inline]
fn detach_thread(
&mut self,
thread_id: ThreadId,
allow_terminated_joined: bool,
) -> InterpResult<'tcx> {
let this = self.eval_context_mut();
this.machine.threads.detach_thread(thread_id, allow_terminated_joined)
}
#[inline]
fn join_thread(&mut self, joined_thread_id: ThreadId) -> InterpResult<'tcx> {
let this = self.eval_context_mut();
this.machine.threads.join_thread(joined_thread_id, this.machine.data_race.as_mut())?;
Ok(())
}
#[inline]
fn join_thread_exclusive(&mut self, joined_thread_id: ThreadId) -> InterpResult<'tcx> {
let this = self.eval_context_mut();
this.machine
.threads
.join_thread_exclusive(joined_thread_id, this.machine.data_race.as_mut())?;
Ok(())
}
#[inline]
fn set_active_thread(&mut self, thread_id: ThreadId) -> ThreadId {
let this = self.eval_context_mut();
this.machine.threads.set_active_thread_id(thread_id)
}
#[inline]
fn get_active_thread(&self) -> ThreadId {
let this = self.eval_context_ref();
this.machine.threads.get_active_thread_id()
}
#[inline]
fn active_thread_mut(&mut self) -> &mut Thread<'mir, 'tcx> {
let this = self.eval_context_mut();
this.machine.threads.active_thread_mut()
}
#[inline]
fn active_thread_ref(&self) -> &Thread<'mir, 'tcx> {
let this = self.eval_context_ref();
this.machine.threads.active_thread_ref()
}
#[inline]
fn get_total_thread_count(&self) -> usize {
let this = self.eval_context_ref();
this.machine.threads.get_total_thread_count()
}
#[inline]
fn have_all_terminated(&self) -> bool {
let this = self.eval_context_ref();
this.machine.threads.have_all_terminated()
}
#[inline]
fn enable_thread(&mut self, thread_id: ThreadId) {
let this = self.eval_context_mut();
this.machine.threads.enable_thread(thread_id);
}
#[inline]
fn active_thread_stack(&self) -> &[Frame<'mir, 'tcx, Provenance, FrameExtra<'tcx>>] {
let this = self.eval_context_ref();
this.machine.threads.active_thread_stack()
}
#[inline]
fn active_thread_stack_mut(
&mut self,
) -> &mut Vec<Frame<'mir, 'tcx, Provenance, FrameExtra<'tcx>>> {
let this = self.eval_context_mut();
this.machine.threads.active_thread_stack_mut()
}
/// Set the name of the current thread. The buffer must not include the null terminator.
#[inline]
fn set_thread_name(&mut self, thread: ThreadId, new_thread_name: Vec<u8>) {
let this = self.eval_context_mut();
this.machine.threads.set_thread_name(thread, new_thread_name);
}
#[inline]
fn set_thread_name_wide(&mut self, thread: ThreadId, new_thread_name: &[u16]) {
let this = self.eval_context_mut();
// The Windows `GetThreadDescription` shim to get the thread name isn't implemented, so being lossy is okay.
// This is only read by diagnostics, which already use `from_utf8_lossy`.
this.machine
.threads
.set_thread_name(thread, String::from_utf16_lossy(new_thread_name).into_bytes());
}
#[inline]
fn get_thread_name<'c>(&'c self, thread: ThreadId) -> &'c [u8]
where
'mir: 'c,
{
self.eval_context_ref().machine.threads.get_thread_name(thread)
}
#[inline]
fn block_thread(&mut self, thread: ThreadId) {
self.eval_context_mut().machine.threads.block_thread(thread);
}
#[inline]
fn unblock_thread(&mut self, thread: ThreadId) {
self.eval_context_mut().machine.threads.unblock_thread(thread);
}
#[inline]
fn yield_active_thread(&mut self) {
self.eval_context_mut().machine.threads.yield_active_thread();
}
#[inline]
fn maybe_preempt_active_thread(&mut self) {
use rand::Rng as _;
let this = self.eval_context_mut();
if this.machine.rng.get_mut().gen_bool(this.machine.preemption_rate) {
this.yield_active_thread();
}
}
#[inline]
fn register_timeout_callback(
&mut self,
thread: ThreadId,
call_time: Time,
callback: TimeoutCallback<'mir, 'tcx>,
) {
let this = self.eval_context_mut();
if !this.machine.communicate() && matches!(call_time, Time::RealTime(..)) {
panic!("cannot have `RealTime` callback with isolation enabled!")
}
this.machine.threads.register_timeout_callback(thread, call_time, callback);
}
#[inline]
fn unregister_timeout_callback_if_exists(&mut self, thread: ThreadId) {
let this = self.eval_context_mut();
this.machine.threads.unregister_timeout_callback_if_exists(thread);
}
/// Run the core interpreter loop. Returns only when an interrupt occurs (an error or program
/// termination).
fn run_threads(&mut self) -> InterpResult<'tcx, !> {
static SIGNALED: AtomicBool = AtomicBool::new(false);
ctrlc::set_handler(move || {
// Indicate that we have ben signaled to stop. If we were already signaled, exit
// immediately. In our interpreter loop we try to consult this value often, but if for
// whatever reason we don't get to that check or the cleanup we do upon finding that
// this bool has become true takes a long time, the exit here will promptly exit the
// process on the second Ctrl-C.
if SIGNALED.swap(true, Relaxed) {
std::process::exit(1);
}
})
.unwrap();
let this = self.eval_context_mut();
loop {
if SIGNALED.load(Relaxed) {
this.machine.handle_abnormal_termination();
std::process::exit(1);
}
match this.machine.threads.schedule(&this.machine.clock)? {
SchedulingAction::ExecuteStep => {
if !this.step()? {
// See if this thread can do something else.
match this.run_on_stack_empty()? {
Poll::Pending => {} // keep going
Poll::Ready(()) => this.terminate_active_thread()?,
}
}
}
SchedulingAction::ExecuteTimeoutCallback => {
this.run_timeout_callback()?;
}
SchedulingAction::Sleep(duration) => {
this.machine.clock.sleep(duration);
}
}
}
}
/// Handles thread termination of the active thread: wakes up threads joining on this one,
/// and deallocated thread-local statics.
///
/// This is called by the eval loop when a thread's on_stack_empty returns `Ready`.
#[inline]
fn terminate_active_thread(&mut self) -> InterpResult<'tcx> {
let this = self.eval_context_mut();
let thread = this.active_thread_mut();
assert!(thread.stack.is_empty(), "only threads with an empty stack can be terminated");
thread.state = ThreadState::Terminated;
let current_span = this.machine.current_span();
for ptr in
this.machine.threads.thread_terminated(this.machine.data_race.as_mut(), current_span)
{
this.deallocate_ptr(ptr.into(), None, MiriMemoryKind::Tls.into())?;
}
Ok(())
}
}