1 //! Implementation of a data-race detector using Lamport Timestamps / Vector-clocks
2 //! based on the Dynamic Race Detection for C++:
3 //! <https://www.doc.ic.ac.uk/~afd/homepages/papers/pdfs/2017/POPL.pdf>
4 //! which does not report false-positives when fences are used, and gives better
5 //! accuracy in presence of read-modify-write operations.
7 //! The implementation contains modifications to correctly model the changes to the memory model in C++20
8 //! regarding the weakening of release sequences: <http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p0982r1.html>.
9 //! Relaxed stores now unconditionally block all currently active release sequences and so per-thread tracking of release
10 //! sequences is not needed.
12 //! The implementation also models races with memory allocation and deallocation via treating allocation and
13 //! deallocation as a type of write internally for detecting data-races.
15 //! Weak memory orders are explored but not all weak behaviours are exhibited, so it can still miss data-races
16 //! but should not report false-positives
18 //! Data-race definition from(<https://en.cppreference.com/w/cpp/language/memory_model#Threads_and_data_races>):
19 //! a data race occurs between two memory accesses if they are on different threads, at least one operation
20 //! is non-atomic, at least one operation is a write and neither access happens-before the other. Read the link
21 //! for full definition.
23 //! This re-uses vector indexes for threads that are known to be unable to report data-races, this is valid
24 //! because it only re-uses vector indexes once all currently-active (not-terminated) threads have an internal
25 //! vector clock that happens-after the join operation of the candidate thread. Threads that have not been joined
26 //! on are not considered. Since the thread's vector clock will only increase and a data-race implies that
27 //! there is some index x where clock\[x\] > thread_clock, when this is true clock\[candidate-idx\] > thread_clock
28 //! can never hold and hence a data-race can never be reported in that vector index again.
29 //! This means that the thread-index can be safely re-used, starting on the next timestamp for the newly created
32 //! The timestamps used in the data-race detector assign each sequence of non-atomic operations
33 //! followed by a single atomic or concurrent operation a single timestamp.
34 //! Write, Read, Write, ThreadJoin will be represented by a single timestamp value on a thread.
35 //! This is because extra increment operations between the operations in the sequence are not
36 //! required for accurate reporting of data-race values.
38 //! As per the paper a threads timestamp is only incremented after a release operation is performed
39 //! so some atomic operations that only perform acquires do not increment the timestamp. Due to shared
40 //! code some atomic operations may increment the timestamp when not necessary but this has no effect
41 //! on the data-race detection code.
44 //! currently we have our own local copy of the currently active thread index and names, this is due
45 //! in part to the inability to access the current location of threads.active_thread inside the AllocExtra
46 //! read, write and deallocate functions and should be cleaned up in the future.
49 cell::{Cell, Ref, RefCell, RefMut},
54 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
55 use rustc_index::vec::{Idx, IndexVec};
56 use rustc_middle::{mir, ty::layout::TyAndLayout};
57 use rustc_target::abi::Size;
61 use super::weak_memory::EvalContextExt as _;
63 pub type AllocExtra = VClockAlloc;
65 /// Valid atomic read-write operations, alias of atomic::Ordering (not non-exhaustive).
66 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
75 /// Valid atomic read operations, subset of atomic::Ordering.
76 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
77 pub enum AtomicReadOp {
83 /// Valid atomic write operations, subset of atomic::Ordering.
84 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
85 pub enum AtomicWriteOp {
91 /// Valid atomic fence operations, subset of atomic::Ordering.
92 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
93 pub enum AtomicFenceOp {
100 /// The current set of vector clocks describing the state
101 /// of a thread, contains the happens-before clock and
102 /// additional metadata to model atomic fence operations.
103 #[derive(Clone, Default, Debug)]
104 pub(super) struct ThreadClockSet {
105 /// The increasing clock representing timestamps
106 /// that happen-before this thread.
107 pub(super) clock: VClock,
109 /// The set of timestamps that will happen-before this
110 /// thread once it performs an acquire fence.
111 fence_acquire: VClock,
113 /// The last timestamp of happens-before relations that
114 /// have been released by this thread by a fence.
115 fence_release: VClock,
117 /// Timestamps of the last SC fence performed by each
118 /// thread, updated when this thread performs an SC fence
119 pub(super) fence_seqcst: VClock,
121 /// Timestamps of the last SC write performed by each
122 /// thread, updated when this thread performs an SC fence
123 pub(super) write_seqcst: VClock,
125 /// Timestamps of the last SC fence performed by each
126 /// thread, updated when this thread performs an SC read
127 pub(super) read_seqcst: VClock,
130 impl ThreadClockSet {
131 /// Apply the effects of a release fence to this
132 /// set of thread vector clocks.
134 fn apply_release_fence(&mut self) {
135 self.fence_release.clone_from(&self.clock);
138 /// Apply the effects of an acquire fence to this
139 /// set of thread vector clocks.
141 fn apply_acquire_fence(&mut self) {
142 self.clock.join(&self.fence_acquire);
145 /// Increment the happens-before clock at a
148 fn increment_clock(&mut self, index: VectorIdx) {
149 self.clock.increment_index(index);
152 /// Join the happens-before clock with that of
153 /// another thread, used to model thread join
155 fn join_with(&mut self, other: &ThreadClockSet) {
156 self.clock.join(&other.clock);
160 /// Error returned by finding a data race
161 /// should be elaborated upon.
162 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
165 /// Externally stored memory cell clocks
166 /// explicitly to reduce memory usage for the
167 /// common case where no atomic operations
168 /// exists on the memory cell.
169 #[derive(Clone, PartialEq, Eq, Default, Debug)]
170 struct AtomicMemoryCellClocks {
171 /// The clock-vector of the timestamp of the last atomic
172 /// read operation performed by each thread.
173 /// This detects potential data-races between atomic read
174 /// and non-atomic write operations.
177 /// The clock-vector of the timestamp of the last atomic
178 /// write operation performed by each thread.
179 /// This detects potential data-races between atomic write
180 /// and non-atomic read or write operations.
181 write_vector: VClock,
183 /// Synchronization vector for acquire-release semantics
184 /// contains the vector of timestamps that will
185 /// happen-before a thread if an acquire-load is
186 /// performed on the data.
190 /// Type of write operation: allocating memory
191 /// non-atomic writes and deallocating memory
192 /// are all treated as writes for the purpose
193 /// of the data-race detector.
194 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
199 /// Standard unsynchronized write.
202 /// Deallocate memory.
203 /// Note that when memory is deallocated first, later non-atomic accesses
204 /// will be reported as use-after-free, not as data races.
205 /// (Same for `Allocate` above.)
209 fn get_descriptor(self) -> &'static str {
211 WriteType::Allocate => "Allocate",
212 WriteType::Write => "Write",
213 WriteType::Deallocate => "Deallocate",
218 /// Memory Cell vector clock metadata
219 /// for data-race detection.
220 #[derive(Clone, PartialEq, Eq, Debug)]
221 struct MemoryCellClocks {
222 /// The vector-clock timestamp of the last write
223 /// corresponding to the writing threads timestamp.
226 /// The identifier of the vector index, corresponding to a thread
227 /// that performed the last write operation.
228 write_index: VectorIdx,
230 /// The type of operation that the write index represents,
231 /// either newly allocated memory, a non-atomic write or
232 /// a deallocation of memory.
233 write_type: WriteType,
235 /// The vector-clock of the timestamp of the last read operation
236 /// performed by a thread since the last write operation occurred.
237 /// It is reset to zero on each write operation.
240 /// Atomic acquire & release sequence tracking clocks.
241 /// For non-atomic memory in the common case this
242 /// value is set to None.
243 atomic_ops: Option<Box<AtomicMemoryCellClocks>>,
246 impl MemoryCellClocks {
247 /// Create a new set of clocks representing memory allocated
248 /// at a given vector timestamp and index.
249 fn new(alloc: VTimestamp, alloc_index: VectorIdx) -> Self {
251 read: VClock::default(),
253 write_index: alloc_index,
254 write_type: WriteType::Allocate,
259 /// Load the internal atomic memory cells if they exist.
261 fn atomic(&self) -> Option<&AtomicMemoryCellClocks> {
262 match &self.atomic_ops {
263 Some(op) => Some(&*op),
268 /// Load or create the internal atomic memory metadata
269 /// if it does not exist.
271 fn atomic_mut(&mut self) -> &mut AtomicMemoryCellClocks {
272 self.atomic_ops.get_or_insert_with(Default::default)
275 /// Update memory cell data-race tracking for atomic
276 /// load acquire semantics, is a no-op if this memory was
277 /// not used previously as atomic memory.
280 clocks: &mut ThreadClockSet,
282 ) -> Result<(), DataRace> {
283 self.atomic_read_detect(clocks, index)?;
284 if let Some(atomic) = self.atomic() {
285 clocks.clock.join(&atomic.sync_vector);
290 /// Update memory cell data-race tracking for atomic
291 /// load relaxed semantics, is a no-op if this memory was
292 /// not used previously as atomic memory.
295 clocks: &mut ThreadClockSet,
297 ) -> Result<(), DataRace> {
298 self.atomic_read_detect(clocks, index)?;
299 if let Some(atomic) = self.atomic() {
300 clocks.fence_acquire.join(&atomic.sync_vector);
305 /// Update the memory cell data-race tracking for atomic
306 /// store release semantics.
307 fn store_release(&mut self, clocks: &ThreadClockSet, index: VectorIdx) -> Result<(), DataRace> {
308 self.atomic_write_detect(clocks, index)?;
309 let atomic = self.atomic_mut();
310 atomic.sync_vector.clone_from(&clocks.clock);
314 /// Update the memory cell data-race tracking for atomic
315 /// store relaxed semantics.
316 fn store_relaxed(&mut self, clocks: &ThreadClockSet, index: VectorIdx) -> Result<(), DataRace> {
317 self.atomic_write_detect(clocks, index)?;
319 // The handling of release sequences was changed in C++20 and so
320 // the code here is different to the paper since now all relaxed
321 // stores block release sequences. The exception for same-thread
322 // relaxed stores has been removed.
323 let atomic = self.atomic_mut();
324 atomic.sync_vector.clone_from(&clocks.fence_release);
328 /// Update the memory cell data-race tracking for atomic
329 /// store release semantics for RMW operations.
330 fn rmw_release(&mut self, clocks: &ThreadClockSet, index: VectorIdx) -> Result<(), DataRace> {
331 self.atomic_write_detect(clocks, index)?;
332 let atomic = self.atomic_mut();
333 atomic.sync_vector.join(&clocks.clock);
337 /// Update the memory cell data-race tracking for atomic
338 /// store relaxed semantics for RMW operations.
339 fn rmw_relaxed(&mut self, clocks: &ThreadClockSet, index: VectorIdx) -> Result<(), DataRace> {
340 self.atomic_write_detect(clocks, index)?;
341 let atomic = self.atomic_mut();
342 atomic.sync_vector.join(&clocks.fence_release);
346 /// Detect data-races with an atomic read, caused by a non-atomic write that does
347 /// not happen-before the atomic-read.
348 fn atomic_read_detect(
350 clocks: &ThreadClockSet,
352 ) -> Result<(), DataRace> {
353 log::trace!("Atomic read with vectors: {:#?} :: {:#?}", self, clocks);
354 if self.write <= clocks.clock[self.write_index] {
355 let atomic = self.atomic_mut();
356 atomic.read_vector.set_at_index(&clocks.clock, index);
363 /// Detect data-races with an atomic write, either with a non-atomic read or with
364 /// a non-atomic write.
365 fn atomic_write_detect(
367 clocks: &ThreadClockSet,
369 ) -> Result<(), DataRace> {
370 log::trace!("Atomic write with vectors: {:#?} :: {:#?}", self, clocks);
371 if self.write <= clocks.clock[self.write_index] && self.read <= clocks.clock {
372 let atomic = self.atomic_mut();
373 atomic.write_vector.set_at_index(&clocks.clock, index);
380 /// Detect races for non-atomic read operations at the current memory cell
381 /// returns true if a data-race is detected.
384 clocks: &ThreadClockSet,
386 ) -> Result<(), DataRace> {
387 log::trace!("Unsynchronized read with vectors: {:#?} :: {:#?}", self, clocks);
388 if self.write <= clocks.clock[self.write_index] {
389 let race_free = if let Some(atomic) = self.atomic() {
390 atomic.write_vector <= clocks.clock
395 self.read.set_at_index(&clocks.clock, index);
405 /// Detect races for non-atomic write operations at the current memory cell
406 /// returns true if a data-race is detected.
407 fn write_race_detect(
409 clocks: &ThreadClockSet,
411 write_type: WriteType,
412 ) -> Result<(), DataRace> {
413 log::trace!("Unsynchronized write with vectors: {:#?} :: {:#?}", self, clocks);
414 if self.write <= clocks.clock[self.write_index] && self.read <= clocks.clock {
415 let race_free = if let Some(atomic) = self.atomic() {
416 atomic.write_vector <= clocks.clock && atomic.read_vector <= clocks.clock
421 self.write = clocks.clock[index];
422 self.write_index = index;
423 self.write_type = write_type;
424 self.read.set_zero_vector();
435 /// Evaluation context extensions.
436 impl<'mir, 'tcx: 'mir> EvalContextExt<'mir, 'tcx> for MiriEvalContext<'mir, 'tcx> {}
437 pub trait EvalContextExt<'mir, 'tcx: 'mir>: MiriEvalContextExt<'mir, 'tcx> {
438 /// Temporarily allow data-races to occur. This should only be used in
439 /// one of these cases:
440 /// - One of the appropriate `validate_atomic` functions will be called to
441 /// to treat a memory access as atomic.
442 /// - The memory being accessed should be treated as internal state, that
443 /// cannot be accessed by the interpreted program.
444 /// - Execution of the interpreted program execution has halted.
446 fn allow_data_races_ref<R>(&self, op: impl FnOnce(&MiriEvalContext<'mir, 'tcx>) -> R) -> R {
447 let this = self.eval_context_ref();
448 let old = if let Some(data_race) = &this.machine.data_race {
449 data_race.multi_threaded.replace(false)
453 let result = op(this);
454 if let Some(data_race) = &this.machine.data_race {
455 data_race.multi_threaded.set(old);
460 /// Same as `allow_data_races_ref`, this temporarily disables any data-race detection and
461 /// so should only be used for atomic operations or internal state that the program cannot
464 fn allow_data_races_mut<R>(
466 op: impl FnOnce(&mut MiriEvalContext<'mir, 'tcx>) -> R,
468 let this = self.eval_context_mut();
469 let old = if let Some(data_race) = &this.machine.data_race {
470 data_race.multi_threaded.replace(false)
474 let result = op(this);
475 if let Some(data_race) = &this.machine.data_race {
476 data_race.multi_threaded.set(old);
481 /// Atomic variant of read_scalar_at_offset.
482 fn read_scalar_at_offset_atomic(
484 op: &OpTy<'tcx, Tag>,
486 layout: TyAndLayout<'tcx>,
487 atomic: AtomicReadOp,
488 ) -> InterpResult<'tcx, ScalarMaybeUninit<Tag>> {
489 let this = self.eval_context_ref();
490 let value_place = this.deref_operand_and_offset(op, offset, layout)?;
491 this.read_scalar_atomic(&value_place, atomic)
494 /// Atomic variant of write_scalar_at_offset.
495 fn write_scalar_at_offset_atomic(
497 op: &OpTy<'tcx, Tag>,
499 value: impl Into<ScalarMaybeUninit<Tag>>,
500 layout: TyAndLayout<'tcx>,
501 atomic: AtomicWriteOp,
502 ) -> InterpResult<'tcx> {
503 let this = self.eval_context_mut();
504 let value_place = this.deref_operand_and_offset(op, offset, layout)?;
505 this.write_scalar_atomic(value.into(), &value_place, atomic)
508 /// Perform an atomic read operation at the memory location.
509 fn read_scalar_atomic(
511 place: &MPlaceTy<'tcx, Tag>,
512 atomic: AtomicReadOp,
513 ) -> InterpResult<'tcx, ScalarMaybeUninit<Tag>> {
514 let this = self.eval_context_ref();
515 // This will read from the last store in the modification order of this location. In case
516 // weak memory emulation is enabled, this may not be the store we will pick to actually read from and return.
517 // This is fine with StackedBorrow and race checks because they don't concern metadata on
518 // the *value* (including the associated provenance if this is an AtomicPtr) at this location.
519 // Only metadata on the location itself is used.
520 let scalar = this.allow_data_races_ref(move |this| this.read_scalar(&place.into()))?;
521 this.buffered_atomic_read(place, atomic, scalar, || {
522 this.validate_atomic_load(place, atomic)
526 /// Perform an atomic write operation at the memory location.
527 fn write_scalar_atomic(
529 val: ScalarMaybeUninit<Tag>,
530 dest: &MPlaceTy<'tcx, Tag>,
531 atomic: AtomicWriteOp,
532 ) -> InterpResult<'tcx> {
533 let this = self.eval_context_mut();
534 this.allow_data_races_mut(move |this| this.write_scalar(val, &(*dest).into()))?;
535 this.validate_atomic_store(dest, atomic)?;
536 this.buffered_atomic_write(val, dest, atomic)
539 /// Perform an atomic operation on a memory location.
540 fn atomic_op_immediate(
542 place: &MPlaceTy<'tcx, Tag>,
543 rhs: &ImmTy<'tcx, Tag>,
547 ) -> InterpResult<'tcx, ImmTy<'tcx, Tag>> {
548 let this = self.eval_context_mut();
550 let old = this.allow_data_races_mut(|this| this.read_immediate(&place.into()))?;
552 // Atomics wrap around on overflow.
553 let val = this.binary_op(op, &old, rhs)?;
554 let val = if neg { this.unary_op(mir::UnOp::Not, &val)? } else { val };
555 this.allow_data_races_mut(|this| this.write_immediate(*val, &(*place).into()))?;
557 this.validate_atomic_rmw(place, atomic)?;
559 this.buffered_atomic_rmw(val.to_scalar_or_uninit(), place, atomic)?;
563 /// Perform an atomic exchange with a memory place and a new
564 /// scalar value, the old value is returned.
565 fn atomic_exchange_scalar(
567 place: &MPlaceTy<'tcx, Tag>,
568 new: ScalarMaybeUninit<Tag>,
570 ) -> InterpResult<'tcx, ScalarMaybeUninit<Tag>> {
571 let this = self.eval_context_mut();
573 let old = this.allow_data_races_mut(|this| this.read_scalar(&place.into()))?;
574 this.allow_data_races_mut(|this| this.write_scalar(new, &(*place).into()))?;
576 this.validate_atomic_rmw(place, atomic)?;
578 this.buffered_atomic_rmw(new, place, atomic)?;
582 /// Perform an conditional atomic exchange with a memory place and a new
583 /// scalar value, the old value is returned.
584 fn atomic_min_max_scalar(
586 place: &MPlaceTy<'tcx, Tag>,
587 rhs: ImmTy<'tcx, Tag>,
590 ) -> InterpResult<'tcx, ImmTy<'tcx, Tag>> {
591 let this = self.eval_context_mut();
593 let old = this.allow_data_races_mut(|this| this.read_immediate(&place.into()))?;
594 let lt = this.binary_op(mir::BinOp::Lt, &old, &rhs)?.to_scalar()?.to_bool()?;
596 let new_val = if min {
597 if lt { &old } else { &rhs }
599 if lt { &rhs } else { &old }
602 this.allow_data_races_mut(|this| this.write_immediate(**new_val, &(*place).into()))?;
604 this.validate_atomic_rmw(place, atomic)?;
606 this.buffered_atomic_rmw(new_val.to_scalar_or_uninit(), place, atomic)?;
608 // Return the old value.
612 /// Perform an atomic compare and exchange at a given memory location.
613 /// On success an atomic RMW operation is performed and on failure
614 /// only an atomic read occurs. If `can_fail_spuriously` is true,
615 /// then we treat it as a "compare_exchange_weak" operation, and
616 /// some portion of the time fail even when the values are actually
618 fn atomic_compare_exchange_scalar(
620 place: &MPlaceTy<'tcx, Tag>,
621 expect_old: &ImmTy<'tcx, Tag>,
622 new: ScalarMaybeUninit<Tag>,
625 can_fail_spuriously: bool,
626 ) -> InterpResult<'tcx, Immediate<Tag>> {
628 let this = self.eval_context_mut();
630 // Failure ordering cannot be stronger than success ordering, therefore first attempt
631 // to read with the failure ordering and if successful then try again with the success
632 // read ordering and write in the success case.
633 // Read as immediate for the sake of `binary_op()`
634 let old = this.allow_data_races_mut(|this| this.read_immediate(&(place.into())))?;
635 // `binary_op` will bail if either of them is not a scalar.
636 let eq = this.binary_op(mir::BinOp::Eq, &old, expect_old)?;
637 // If the operation would succeed, but is "weak", fail some portion
638 // of the time, based on `success_rate`.
639 let success_rate = 1.0 - this.machine.cmpxchg_weak_failure_rate;
640 let cmpxchg_success = eq.to_scalar()?.to_bool()?
641 && if can_fail_spuriously {
642 this.machine.rng.get_mut().gen_bool(success_rate)
646 let res = Immediate::ScalarPair(
647 old.to_scalar_or_uninit(),
648 Scalar::from_bool(cmpxchg_success).into(),
651 // Update ptr depending on comparison.
652 // if successful, perform a full rw-atomic validation
653 // otherwise treat this as an atomic load with the fail ordering.
655 this.allow_data_races_mut(|this| this.write_scalar(new, &(*place).into()))?;
656 this.validate_atomic_rmw(place, success)?;
657 this.buffered_atomic_rmw(new, place, success)?;
659 this.validate_atomic_load(place, fail)?;
660 // A failed compare exchange is equivalent to a load, reading from the latest store
661 // in the modification order.
662 // Since `old` is only a value and not the store element, we need to separately
663 // find it in our store buffer and perform load_impl on it.
664 this.perform_read_on_buffered_latest(place, fail)?;
667 // Return the old value.
671 /// Update the data-race detector for an atomic read occurring at the
672 /// associated memory-place and on the current thread.
673 fn validate_atomic_load(
675 place: &MPlaceTy<'tcx, Tag>,
676 atomic: AtomicReadOp,
677 ) -> InterpResult<'tcx> {
678 let this = self.eval_context_ref();
679 this.validate_atomic_op(
683 move |memory, clocks, index, atomic| {
684 if atomic == AtomicReadOp::Relaxed {
685 memory.load_relaxed(&mut *clocks, index)
687 memory.load_acquire(&mut *clocks, index)
693 /// Update the data-race detector for an atomic write occurring at the
694 /// associated memory-place and on the current thread.
695 fn validate_atomic_store(
697 place: &MPlaceTy<'tcx, Tag>,
698 atomic: AtomicWriteOp,
699 ) -> InterpResult<'tcx> {
700 let this = self.eval_context_mut();
701 this.validate_atomic_op(
705 move |memory, clocks, index, atomic| {
706 if atomic == AtomicWriteOp::Relaxed {
707 memory.store_relaxed(clocks, index)
709 memory.store_release(clocks, index)
715 /// Update the data-race detector for an atomic read-modify-write occurring
716 /// at the associated memory place and on the current thread.
717 fn validate_atomic_rmw(
719 place: &MPlaceTy<'tcx, Tag>,
721 ) -> InterpResult<'tcx> {
723 let acquire = matches!(atomic, Acquire | AcqRel | SeqCst);
724 let release = matches!(atomic, Release | AcqRel | SeqCst);
725 let this = self.eval_context_mut();
726 this.validate_atomic_op(place, atomic, "Atomic RMW", move |memory, clocks, index, _| {
728 memory.load_acquire(clocks, index)?;
730 memory.load_relaxed(clocks, index)?;
733 memory.rmw_release(clocks, index)
735 memory.rmw_relaxed(clocks, index)
740 /// Update the data-race detector for an atomic fence on the current thread.
741 fn validate_atomic_fence(&mut self, atomic: AtomicFenceOp) -> InterpResult<'tcx> {
742 let this = self.eval_context_mut();
743 if let Some(data_race) = &mut this.machine.data_race {
744 data_race.maybe_perform_sync_operation(|index, mut clocks| {
745 log::trace!("Atomic fence on {:?} with ordering {:?}", index, atomic);
747 // Apply data-race detection for the current fences
748 // this treats AcqRel and SeqCst as the same as an acquire
749 // and release fence applied in the same timestamp.
750 if atomic != AtomicFenceOp::Release {
751 // Either Acquire | AcqRel | SeqCst
752 clocks.apply_acquire_fence();
754 if atomic != AtomicFenceOp::Acquire {
755 // Either Release | AcqRel | SeqCst
756 clocks.apply_release_fence();
758 if atomic == AtomicFenceOp::SeqCst {
759 data_race.last_sc_fence.borrow_mut().set_at_index(&clocks.clock, index);
760 clocks.fence_seqcst.join(&data_race.last_sc_fence.borrow());
761 clocks.write_seqcst.join(&data_race.last_sc_write.borrow());
764 // Increment timestamp in case of release semantics.
765 Ok(atomic != AtomicFenceOp::Acquire)
773 /// Vector clock metadata for a logical memory allocation.
774 #[derive(Debug, Clone)]
775 pub struct VClockAlloc {
776 /// Assigning each byte a MemoryCellClocks.
777 alloc_ranges: RefCell<RangeMap<MemoryCellClocks>>,
781 /// Create a new data-race detector for newly allocated memory.
782 pub fn new_allocation(
783 global: &GlobalState,
785 kind: MemoryKind<MiriMemoryKind>,
787 let (alloc_timestamp, alloc_index) = match kind {
788 // User allocated and stack memory should track allocation.
790 MiriMemoryKind::Rust | MiriMemoryKind::C | MiriMemoryKind::WinHeap,
792 | MemoryKind::Stack => {
793 let (alloc_index, clocks) = global.current_thread_state();
794 let alloc_timestamp = clocks.clock[alloc_index];
795 (alloc_timestamp, alloc_index)
797 // Other global memory should trace races but be allocated at the 0 timestamp.
799 MiriMemoryKind::Global
800 | MiriMemoryKind::Machine
801 | MiriMemoryKind::Runtime
802 | MiriMemoryKind::ExternStatic
803 | MiriMemoryKind::Tls,
805 | MemoryKind::CallerLocation => (0, VectorIdx::MAX_INDEX),
808 alloc_ranges: RefCell::new(RangeMap::new(
810 MemoryCellClocks::new(alloc_timestamp, alloc_index),
815 // Find an index, if one exists where the value
816 // in `l` is greater than the value in `r`.
817 fn find_gt_index(l: &VClock, r: &VClock) -> Option<VectorIdx> {
818 log::trace!("Find index where not {:?} <= {:?}", l, r);
819 let l_slice = l.as_slice();
820 let r_slice = r.as_slice();
825 .find_map(|(idx, (&l, &r))| if l > r { Some(idx) } else { None })
827 if l_slice.len() > r_slice.len() {
828 // By invariant, if l_slice is longer
829 // then one element must be larger.
830 // This just validates that this is true
831 // and reports earlier elements first.
832 let l_remainder_slice = &l_slice[r_slice.len()..];
833 let idx = l_remainder_slice
836 .find_map(|(idx, &r)| if r == 0 { None } else { Some(idx) })
837 .expect("Invalid VClock Invariant");
838 Some(idx + r_slice.len())
846 /// Report a data-race found in the program.
847 /// This finds the two racing threads and the type
848 /// of data-race that occurred. This will also
849 /// return info about the memory location the data-race
853 fn report_data_race<'tcx>(
854 global: &GlobalState,
855 range: &MemoryCellClocks,
858 ptr_dbg: Pointer<AllocId>,
859 ) -> InterpResult<'tcx> {
860 let (current_index, current_clocks) = global.current_thread_state();
862 let (other_action, other_thread, other_clock) = if range.write
863 > current_clocks.clock[range.write_index]
865 // Convert the write action into the vector clock it
866 // represents for diagnostic purposes.
867 write_clock = VClock::new_with_index(range.write_index, range.write);
868 (range.write_type.get_descriptor(), range.write_index, &write_clock)
869 } else if let Some(idx) = Self::find_gt_index(&range.read, ¤t_clocks.clock) {
870 ("Read", idx, &range.read)
871 } else if !is_atomic {
872 if let Some(atomic) = range.atomic() {
873 if let Some(idx) = Self::find_gt_index(&atomic.write_vector, ¤t_clocks.clock)
875 ("Atomic Store", idx, &atomic.write_vector)
876 } else if let Some(idx) =
877 Self::find_gt_index(&atomic.read_vector, ¤t_clocks.clock)
879 ("Atomic Load", idx, &atomic.read_vector)
882 "Failed to report data-race for non-atomic operation: no race found"
887 "Failed to report data-race for non-atomic operation: no atomic component"
891 unreachable!("Failed to report data-race for atomic operation")
894 // Load elaborated thread information about the racing thread actions.
895 let current_thread_info = global.print_thread_metadata(current_index);
896 let other_thread_info = global.print_thread_metadata(other_thread);
898 // Throw the data-race detection.
900 "Data race detected between {} on {} and {} on {} at {:?} (current vector clock = {:?}, conflicting timestamp = {:?})",
906 current_clocks.clock,
911 /// Detect data-races for an unsynchronized read operation, will not perform
912 /// data-race detection if `multi-threaded` is false, either due to no threads
913 /// being created or if it is temporarily disabled during a racy read or write
914 /// operation for which data-race detection is handled separately, for example
915 /// atomic read operations.
920 global: &GlobalState,
921 ) -> InterpResult<'tcx> {
922 if global.multi_threaded.get() {
923 let (index, clocks) = global.current_thread_state();
924 let mut alloc_ranges = self.alloc_ranges.borrow_mut();
925 for (offset, range) in alloc_ranges.iter_mut(range.start, range.size) {
926 if let Err(DataRace) = range.read_race_detect(&*clocks, index) {
928 return Self::report_data_race(
933 Pointer::new(alloc_id, offset),
943 // Shared code for detecting data-races on unique access to a section of memory
944 fn unique_access<'tcx>(
948 write_type: WriteType,
949 global: &mut GlobalState,
950 ) -> InterpResult<'tcx> {
951 if global.multi_threaded.get() {
952 let (index, clocks) = global.current_thread_state();
953 for (offset, range) in self.alloc_ranges.get_mut().iter_mut(range.start, range.size) {
954 if let Err(DataRace) = range.write_race_detect(&*clocks, index, write_type) {
956 return Self::report_data_race(
959 write_type.get_descriptor(),
961 Pointer::new(alloc_id, offset),
971 /// Detect data-races for an unsynchronized write operation, will not perform
972 /// data-race threads if `multi-threaded` is false, either due to no threads
973 /// being created or if it is temporarily disabled during a racy read or write
979 global: &mut GlobalState,
980 ) -> InterpResult<'tcx> {
981 self.unique_access(alloc_id, range, WriteType::Write, global)
984 /// Detect data-races for an unsynchronized deallocate operation, will not perform
985 /// data-race threads if `multi-threaded` is false, either due to no threads
986 /// being created or if it is temporarily disabled during a racy read or write
988 pub fn deallocate<'tcx>(
992 global: &mut GlobalState,
993 ) -> InterpResult<'tcx> {
994 self.unique_access(alloc_id, range, WriteType::Deallocate, global)
998 impl<'mir, 'tcx: 'mir> EvalContextPrivExt<'mir, 'tcx> for MiriEvalContext<'mir, 'tcx> {}
999 trait EvalContextPrivExt<'mir, 'tcx: 'mir>: MiriEvalContextExt<'mir, 'tcx> {
1000 /// Generic atomic operation implementation
1001 fn validate_atomic_op<A: Debug + Copy>(
1003 place: &MPlaceTy<'tcx, Tag>,
1007 &mut MemoryCellClocks,
1008 &mut ThreadClockSet,
1011 ) -> Result<(), DataRace>,
1012 ) -> InterpResult<'tcx> {
1013 let this = self.eval_context_ref();
1014 if let Some(data_race) = &this.machine.data_race {
1015 if data_race.multi_threaded.get() {
1016 let size = place.layout.size;
1017 let (alloc_id, base_offset, _tag) = this.ptr_get_alloc_id(place.ptr)?;
1018 // Load and log the atomic operation.
1019 // Note that atomic loads are possible even from read-only allocations, so `get_alloc_extra_mut` is not an option.
1020 let alloc_meta = &this.get_alloc_extra(alloc_id)?.data_race.as_ref().unwrap();
1022 "Atomic op({}) with ordering {:?} on {:?} (size={})",
1029 // Perform the atomic operation.
1030 data_race.maybe_perform_sync_operation(|index, mut clocks| {
1031 for (offset, range) in
1032 alloc_meta.alloc_ranges.borrow_mut().iter_mut(base_offset, size)
1034 if let Err(DataRace) = op(range, &mut *clocks, index, atomic) {
1036 return VClockAlloc::report_data_race(
1041 Pointer::new(alloc_id, offset),
1047 // This conservatively assumes all operations have release semantics
1051 // Log changes to atomic memory.
1052 if log::log_enabled!(log::Level::Trace) {
1053 for (_offset, range) in alloc_meta.alloc_ranges.borrow().iter(base_offset, size)
1056 "Updated atomic memory({:?}, size={}) to {:#?}",
1069 /// Extra metadata associated with a thread.
1070 #[derive(Debug, Clone, Default)]
1071 struct ThreadExtraState {
1072 /// The current vector index in use by the
1073 /// thread currently, this is set to None
1074 /// after the vector index has been re-used
1075 /// and hence the value will never need to be
1076 /// read during data-race reporting.
1077 vector_index: Option<VectorIdx>,
1079 /// The name of the thread, updated for better
1080 /// diagnostics when reporting detected data
1082 thread_name: Option<Box<str>>,
1084 /// Thread termination vector clock, this
1085 /// is set on thread termination and is used
1086 /// for joining on threads since the vector_index
1087 /// may be re-used when the join operation occurs.
1088 termination_vector_clock: Option<VClock>,
1091 /// Global data-race detection state, contains the currently
1092 /// executing thread as well as the vector-clocks associated
1093 /// with each of the threads.
1094 // FIXME: it is probably better to have one large RefCell, than to have so many small ones.
1095 #[derive(Debug, Clone)]
1096 pub struct GlobalState {
1097 /// Set to true once the first additional
1098 /// thread has launched, due to the dependency
1099 /// between before and after a thread launch.
1100 /// Any data-races must be recorded after this
1101 /// so concurrent execution can ignore recording
1103 multi_threaded: Cell<bool>,
1105 /// Mapping of a vector index to a known set of thread
1106 /// clocks, this is not directly mapping from a thread id
1107 /// since it may refer to multiple threads.
1108 vector_clocks: RefCell<IndexVec<VectorIdx, ThreadClockSet>>,
1110 /// Mapping of a given vector index to the current thread
1111 /// that the execution is representing, this may change
1112 /// if a vector index is re-assigned to a new thread.
1113 vector_info: RefCell<IndexVec<VectorIdx, ThreadId>>,
1115 /// The mapping of a given thread to associated thread metadata.
1116 thread_info: RefCell<IndexVec<ThreadId, ThreadExtraState>>,
1118 /// The current vector index being executed.
1119 current_index: Cell<VectorIdx>,
1121 /// Potential vector indices that could be re-used on thread creation
1122 /// values are inserted here on after the thread has terminated and
1123 /// been joined with, and hence may potentially become free
1124 /// for use as the index for a new thread.
1125 /// Elements in this set may still require the vector index to
1126 /// report data-races, and can only be re-used after all
1127 /// active vector-clocks catch up with the threads timestamp.
1128 reuse_candidates: RefCell<FxHashSet<VectorIdx>>,
1130 /// Counts the number of threads that are currently active
1131 /// if the number of active threads reduces to 1 and then
1132 /// a join operation occurs with the remaining main thread
1133 /// then multi-threaded execution may be disabled.
1134 active_thread_count: Cell<usize>,
1136 /// This contains threads that have terminated, but not yet joined
1137 /// and so cannot become re-use candidates until a join operation
1139 /// The associated vector index will be moved into re-use candidates
1140 /// after the join operation occurs.
1141 terminated_threads: RefCell<FxHashMap<ThreadId, VectorIdx>>,
1143 /// The timestamp of last SC fence performed by each thread
1144 last_sc_fence: RefCell<VClock>,
1146 /// The timestamp of last SC write performed by each thread
1147 last_sc_write: RefCell<VClock>,
1151 /// Create a new global state, setup with just thread-id=0
1152 /// advanced to timestamp = 1.
1153 pub fn new() -> Self {
1154 let mut global_state = GlobalState {
1155 multi_threaded: Cell::new(false),
1156 vector_clocks: RefCell::new(IndexVec::new()),
1157 vector_info: RefCell::new(IndexVec::new()),
1158 thread_info: RefCell::new(IndexVec::new()),
1159 current_index: Cell::new(VectorIdx::new(0)),
1160 active_thread_count: Cell::new(1),
1161 reuse_candidates: RefCell::new(FxHashSet::default()),
1162 terminated_threads: RefCell::new(FxHashMap::default()),
1163 last_sc_fence: RefCell::new(VClock::default()),
1164 last_sc_write: RefCell::new(VClock::default()),
1167 // Setup the main-thread since it is not explicitly created:
1168 // uses vector index and thread-id 0, also the rust runtime gives
1169 // the main-thread a name of "main".
1170 let index = global_state.vector_clocks.get_mut().push(ThreadClockSet::default());
1171 global_state.vector_info.get_mut().push(ThreadId::new(0));
1172 global_state.thread_info.get_mut().push(ThreadExtraState {
1173 vector_index: Some(index),
1174 thread_name: Some("main".to_string().into_boxed_str()),
1175 termination_vector_clock: None,
1181 // Try to find vector index values that can potentially be re-used
1182 // by a new thread instead of a new vector index being created.
1183 fn find_vector_index_reuse_candidate(&self) -> Option<VectorIdx> {
1184 let mut reuse = self.reuse_candidates.borrow_mut();
1185 let vector_clocks = self.vector_clocks.borrow();
1186 let vector_info = self.vector_info.borrow();
1187 let terminated_threads = self.terminated_threads.borrow();
1188 for &candidate in reuse.iter() {
1189 let target_timestamp = vector_clocks[candidate].clock[candidate];
1190 if vector_clocks.iter_enumerated().all(|(clock_idx, clock)| {
1191 // The thread happens before the clock, and hence cannot report
1192 // a data-race with this the candidate index.
1193 let no_data_race = clock.clock[candidate] >= target_timestamp;
1195 // The vector represents a thread that has terminated and hence cannot
1196 // report a data-race with the candidate index.
1197 let thread_id = vector_info[clock_idx];
1198 let vector_terminated =
1199 reuse.contains(&clock_idx) || terminated_threads.contains_key(&thread_id);
1201 // The vector index cannot report a race with the candidate index
1202 // and hence allows the candidate index to be re-used.
1203 no_data_race || vector_terminated
1205 // All vector clocks for each vector index are equal to
1206 // the target timestamp, and the thread is known to have
1207 // terminated, therefore this vector clock index cannot
1208 // report any more data-races.
1209 assert!(reuse.remove(&candidate));
1210 return Some(candidate);
1216 // Hook for thread creation, enabled multi-threaded execution and marks
1217 // the current thread timestamp as happening-before the current thread.
1219 pub fn thread_created(&mut self, thread: ThreadId) {
1220 let current_index = self.current_index();
1222 // Increment the number of active threads.
1223 let active_threads = self.active_thread_count.get();
1224 self.active_thread_count.set(active_threads + 1);
1226 // Enable multi-threaded execution, there are now two threads
1227 // so data-races are now possible.
1228 self.multi_threaded.set(true);
1230 // Load and setup the associated thread metadata
1231 let mut thread_info = self.thread_info.borrow_mut();
1232 thread_info.ensure_contains_elem(thread, Default::default);
1234 // Assign a vector index for the thread, attempting to re-use an old
1235 // vector index that can no longer report any data-races if possible.
1236 let created_index = if let Some(reuse_index) = self.find_vector_index_reuse_candidate() {
1237 // Now re-configure the re-use candidate, increment the clock
1238 // for the new sync use of the vector.
1239 let vector_clocks = self.vector_clocks.get_mut();
1240 vector_clocks[reuse_index].increment_clock(reuse_index);
1242 // Locate the old thread the vector was associated with and update
1243 // it to represent the new thread instead.
1244 let vector_info = self.vector_info.get_mut();
1245 let old_thread = vector_info[reuse_index];
1246 vector_info[reuse_index] = thread;
1248 // Mark the thread the vector index was associated with as no longer
1249 // representing a thread index.
1250 thread_info[old_thread].vector_index = None;
1254 // No vector re-use candidates available, instead create
1255 // a new vector index.
1256 let vector_info = self.vector_info.get_mut();
1257 vector_info.push(thread)
1260 log::trace!("Creating thread = {:?} with vector index = {:?}", thread, created_index);
1262 // Mark the chosen vector index as in use by the thread.
1263 thread_info[thread].vector_index = Some(created_index);
1265 // Create a thread clock set if applicable.
1266 let vector_clocks = self.vector_clocks.get_mut();
1267 if created_index == vector_clocks.next_index() {
1268 vector_clocks.push(ThreadClockSet::default());
1271 // Now load the two clocks and configure the initial state.
1272 let (current, created) = vector_clocks.pick2_mut(current_index, created_index);
1274 // Join the created with current, since the current threads
1275 // previous actions happen-before the created thread.
1276 created.join_with(current);
1278 // Advance both threads after the synchronized operation.
1279 // Both operations are considered to have release semantics.
1280 current.increment_clock(current_index);
1281 created.increment_clock(created_index);
1284 /// Hook on a thread join to update the implicit happens-before relation
1285 /// between the joined thread and the current thread.
1287 pub fn thread_joined(&mut self, current_thread: ThreadId, join_thread: ThreadId) {
1288 let clocks_vec = self.vector_clocks.get_mut();
1289 let thread_info = self.thread_info.get_mut();
1291 // Load the vector clock of the current thread.
1292 let current_index = thread_info[current_thread]
1294 .expect("Performed thread join on thread with no assigned vector");
1295 let current = &mut clocks_vec[current_index];
1297 // Load the associated vector clock for the terminated thread.
1298 let join_clock = thread_info[join_thread]
1299 .termination_vector_clock
1301 .expect("Joined with thread but thread has not terminated");
1303 // The join thread happens-before the current thread
1304 // so update the current vector clock.
1305 // Is not a release operation so the clock is not incremented.
1306 current.clock.join(join_clock);
1308 // Check the number of active threads, if the value is 1
1309 // then test for potentially disabling multi-threaded execution.
1310 let active_threads = self.active_thread_count.get();
1311 if active_threads == 1 {
1312 // May potentially be able to disable multi-threaded execution.
1313 let current_clock = &clocks_vec[current_index];
1316 .all(|(idx, clocks)| clocks.clock[idx] <= current_clock.clock[idx])
1318 // All thread terminations happen-before the current clock
1319 // therefore no data-races can be reported until a new thread
1320 // is created, so disable multi-threaded execution.
1321 self.multi_threaded.set(false);
1325 // If the thread is marked as terminated but not joined
1326 // then move the thread to the re-use set.
1327 let termination = self.terminated_threads.get_mut();
1328 if let Some(index) = termination.remove(&join_thread) {
1329 let reuse = self.reuse_candidates.get_mut();
1330 reuse.insert(index);
1334 /// On thread termination, the vector-clock may re-used
1335 /// in the future once all remaining thread-clocks catch
1336 /// up with the time index of the terminated thread.
1337 /// This assigns thread termination with a unique index
1338 /// which will be used to join the thread
1339 /// This should be called strictly before any calls to
1340 /// `thread_joined`.
1342 pub fn thread_terminated(&mut self) {
1343 let current_index = self.current_index();
1345 // Increment the clock to a unique termination timestamp.
1346 let vector_clocks = self.vector_clocks.get_mut();
1347 let current_clocks = &mut vector_clocks[current_index];
1348 current_clocks.increment_clock(current_index);
1350 // Load the current thread id for the executing vector.
1351 let vector_info = self.vector_info.get_mut();
1352 let current_thread = vector_info[current_index];
1354 // Load the current thread metadata, and move to a terminated
1355 // vector state. Setting up the vector clock all join operations
1357 let thread_info = self.thread_info.get_mut();
1358 let current = &mut thread_info[current_thread];
1359 current.termination_vector_clock = Some(current_clocks.clock.clone());
1361 // Add this thread as a candidate for re-use after a thread join
1363 let termination = self.terminated_threads.get_mut();
1364 termination.insert(current_thread, current_index);
1366 // Reduce the number of active threads, now that a thread has
1368 let mut active_threads = self.active_thread_count.get();
1369 active_threads -= 1;
1370 self.active_thread_count.set(active_threads);
1373 /// Hook for updating the local tracker of the currently
1374 /// enabled thread, should always be updated whenever
1375 /// `active_thread` in thread.rs is updated.
1377 pub fn thread_set_active(&self, thread: ThreadId) {
1378 let thread_info = self.thread_info.borrow();
1379 let vector_idx = thread_info[thread]
1381 .expect("Setting thread active with no assigned vector");
1382 self.current_index.set(vector_idx);
1385 /// Hook for updating the local tracker of the threads name
1386 /// this should always mirror the local value in thread.rs
1387 /// the thread name is used for improved diagnostics
1388 /// during a data-race.
1390 pub fn thread_set_name(&mut self, thread: ThreadId, name: String) {
1391 let name = name.into_boxed_str();
1392 let thread_info = self.thread_info.get_mut();
1393 thread_info[thread].thread_name = Some(name);
1396 /// Attempt to perform a synchronized operation, this
1397 /// will perform no operation if multi-threading is
1398 /// not currently enabled.
1399 /// Otherwise it will increment the clock for the current
1400 /// vector before and after the operation for data-race
1401 /// detection between any happens-before edges the
1402 /// operation may create.
1403 fn maybe_perform_sync_operation<'tcx>(
1405 op: impl FnOnce(VectorIdx, RefMut<'_, ThreadClockSet>) -> InterpResult<'tcx, bool>,
1406 ) -> InterpResult<'tcx> {
1407 if self.multi_threaded.get() {
1408 let (index, clocks) = self.current_thread_state_mut();
1409 if op(index, clocks)? {
1410 let (_, mut clocks) = self.current_thread_state_mut();
1411 clocks.increment_clock(index);
1417 /// Internal utility to identify a thread stored internally
1418 /// returns the id and the name for better diagnostics.
1419 fn print_thread_metadata(&self, vector: VectorIdx) -> String {
1420 let thread = self.vector_info.borrow()[vector];
1421 let thread_name = &self.thread_info.borrow()[thread].thread_name;
1422 if let Some(name) = thread_name {
1423 let name: &str = name;
1424 format!("Thread(id = {:?}, name = {:?})", thread.to_u32(), &*name)
1426 format!("Thread(id = {:?})", thread.to_u32())
1430 /// Acquire a lock, express that the previous call of
1431 /// `validate_lock_release` must happen before this.
1432 /// As this is an acquire operation, the thread timestamp is not
1434 pub fn validate_lock_acquire(&self, lock: &VClock, thread: ThreadId) {
1435 let (_, mut clocks) = self.load_thread_state_mut(thread);
1436 clocks.clock.join(lock);
1439 /// Release a lock handle, express that this happens-before
1440 /// any subsequent calls to `validate_lock_acquire`.
1441 /// For normal locks this should be equivalent to `validate_lock_release_shared`
1442 /// since an acquire operation should have occurred before, however
1443 /// for futex & condvar operations this is not the case and this
1444 /// operation must be used.
1445 pub fn validate_lock_release(&self, lock: &mut VClock, thread: ThreadId) {
1446 let (index, mut clocks) = self.load_thread_state_mut(thread);
1447 lock.clone_from(&clocks.clock);
1448 clocks.increment_clock(index);
1451 /// Release a lock handle, express that this happens-before
1452 /// any subsequent calls to `validate_lock_acquire` as well
1453 /// as any previous calls to this function after any
1454 /// `validate_lock_release` calls.
1455 /// For normal locks this should be equivalent to `validate_lock_release`.
1456 /// This function only exists for joining over the set of concurrent readers
1457 /// in a read-write lock and should not be used for anything else.
1458 pub fn validate_lock_release_shared(&self, lock: &mut VClock, thread: ThreadId) {
1459 let (index, mut clocks) = self.load_thread_state_mut(thread);
1460 lock.join(&clocks.clock);
1461 clocks.increment_clock(index);
1464 /// Load the vector index used by the given thread as well as the set of vector clocks
1465 /// used by the thread.
1467 fn load_thread_state_mut(&self, thread: ThreadId) -> (VectorIdx, RefMut<'_, ThreadClockSet>) {
1468 let index = self.thread_info.borrow()[thread]
1470 .expect("Loading thread state for thread with no assigned vector");
1471 let ref_vector = self.vector_clocks.borrow_mut();
1472 let clocks = RefMut::map(ref_vector, |vec| &mut vec[index]);
1476 /// Load the current vector clock in use and the current set of thread clocks
1477 /// in use for the vector.
1479 pub(super) fn current_thread_state(&self) -> (VectorIdx, Ref<'_, ThreadClockSet>) {
1480 let index = self.current_index();
1481 let ref_vector = self.vector_clocks.borrow();
1482 let clocks = Ref::map(ref_vector, |vec| &vec[index]);
1486 /// Load the current vector clock in use and the current set of thread clocks
1487 /// in use for the vector mutably for modification.
1489 pub(super) fn current_thread_state_mut(&self) -> (VectorIdx, RefMut<'_, ThreadClockSet>) {
1490 let index = self.current_index();
1491 let ref_vector = self.vector_clocks.borrow_mut();
1492 let clocks = RefMut::map(ref_vector, |vec| &mut vec[index]);
1496 /// Return the current thread, should be the same
1497 /// as the data-race active thread.
1499 fn current_index(&self) -> VectorIdx {
1500 self.current_index.get()
1503 // SC ATOMIC STORE rule in the paper.
1504 pub(super) fn sc_write(&self) {
1505 let (index, clocks) = self.current_thread_state();
1506 self.last_sc_write.borrow_mut().set_at_index(&clocks.clock, index);
1509 // SC ATOMIC READ rule in the paper.
1510 pub(super) fn sc_read(&self) {
1511 let (.., mut clocks) = self.current_thread_state_mut();
1512 clocks.read_seqcst.join(&self.last_sc_fence.borrow());