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 self.atomic_ops.as_deref()
265 /// Load or create the internal atomic memory metadata
266 /// if it does not exist.
268 fn atomic_mut(&mut self) -> &mut AtomicMemoryCellClocks {
269 self.atomic_ops.get_or_insert_with(Default::default)
272 /// Update memory cell data-race tracking for atomic
273 /// load acquire semantics, is a no-op if this memory was
274 /// not used previously as atomic memory.
277 clocks: &mut ThreadClockSet,
279 ) -> Result<(), DataRace> {
280 self.atomic_read_detect(clocks, index)?;
281 if let Some(atomic) = self.atomic() {
282 clocks.clock.join(&atomic.sync_vector);
287 /// Checks if the memory cell access is ordered with all prior atomic reads and writes
288 fn race_free_with_atomic(&self, clocks: &ThreadClockSet) -> bool {
289 if let Some(atomic) = self.atomic() {
290 atomic.read_vector <= clocks.clock && atomic.write_vector <= clocks.clock
296 /// Update memory cell data-race tracking for atomic
297 /// load relaxed semantics, is a no-op if this memory was
298 /// not used previously as atomic memory.
301 clocks: &mut ThreadClockSet,
303 ) -> Result<(), DataRace> {
304 self.atomic_read_detect(clocks, index)?;
305 if let Some(atomic) = self.atomic() {
306 clocks.fence_acquire.join(&atomic.sync_vector);
311 /// Update the memory cell data-race tracking for atomic
312 /// store release semantics.
313 fn store_release(&mut self, clocks: &ThreadClockSet, index: VectorIdx) -> Result<(), DataRace> {
314 self.atomic_write_detect(clocks, index)?;
315 let atomic = self.atomic_mut();
316 atomic.sync_vector.clone_from(&clocks.clock);
320 /// Update the memory cell data-race tracking for atomic
321 /// store relaxed semantics.
322 fn store_relaxed(&mut self, clocks: &ThreadClockSet, index: VectorIdx) -> Result<(), DataRace> {
323 self.atomic_write_detect(clocks, index)?;
325 // The handling of release sequences was changed in C++20 and so
326 // the code here is different to the paper since now all relaxed
327 // stores block release sequences. The exception for same-thread
328 // relaxed stores has been removed.
329 let atomic = self.atomic_mut();
330 atomic.sync_vector.clone_from(&clocks.fence_release);
334 /// Update the memory cell data-race tracking for atomic
335 /// store release semantics for RMW operations.
336 fn rmw_release(&mut self, clocks: &ThreadClockSet, index: VectorIdx) -> Result<(), DataRace> {
337 self.atomic_write_detect(clocks, index)?;
338 let atomic = self.atomic_mut();
339 atomic.sync_vector.join(&clocks.clock);
343 /// Update the memory cell data-race tracking for atomic
344 /// store relaxed semantics for RMW operations.
345 fn rmw_relaxed(&mut self, clocks: &ThreadClockSet, index: VectorIdx) -> Result<(), DataRace> {
346 self.atomic_write_detect(clocks, index)?;
347 let atomic = self.atomic_mut();
348 atomic.sync_vector.join(&clocks.fence_release);
352 /// Detect data-races with an atomic read, caused by a non-atomic write that does
353 /// not happen-before the atomic-read.
354 fn atomic_read_detect(
356 clocks: &ThreadClockSet,
358 ) -> Result<(), DataRace> {
359 log::trace!("Atomic read with vectors: {:#?} :: {:#?}", self, clocks);
360 if self.write <= clocks.clock[self.write_index] {
361 let atomic = self.atomic_mut();
362 atomic.read_vector.set_at_index(&clocks.clock, index);
369 /// Detect data-races with an atomic write, either with a non-atomic read or with
370 /// a non-atomic write.
371 fn atomic_write_detect(
373 clocks: &ThreadClockSet,
375 ) -> Result<(), DataRace> {
376 log::trace!("Atomic write with vectors: {:#?} :: {:#?}", self, clocks);
377 if self.write <= clocks.clock[self.write_index] && self.read <= clocks.clock {
378 let atomic = self.atomic_mut();
379 atomic.write_vector.set_at_index(&clocks.clock, index);
386 /// Detect races for non-atomic read operations at the current memory cell
387 /// returns true if a data-race is detected.
390 clocks: &ThreadClockSet,
392 ) -> Result<(), DataRace> {
393 log::trace!("Unsynchronized read with vectors: {:#?} :: {:#?}", self, clocks);
394 if self.write <= clocks.clock[self.write_index] {
395 let race_free = if let Some(atomic) = self.atomic() {
396 atomic.write_vector <= clocks.clock
401 self.read.set_at_index(&clocks.clock, index);
411 /// Detect races for non-atomic write operations at the current memory cell
412 /// returns true if a data-race is detected.
413 fn write_race_detect(
415 clocks: &ThreadClockSet,
417 write_type: WriteType,
418 ) -> Result<(), DataRace> {
419 log::trace!("Unsynchronized write with vectors: {:#?} :: {:#?}", self, clocks);
420 if self.write <= clocks.clock[self.write_index] && self.read <= clocks.clock {
421 let race_free = if let Some(atomic) = self.atomic() {
422 atomic.write_vector <= clocks.clock && atomic.read_vector <= clocks.clock
427 self.write = clocks.clock[index];
428 self.write_index = index;
429 self.write_type = write_type;
430 self.read.set_zero_vector();
441 /// Evaluation context extensions.
442 impl<'mir, 'tcx: 'mir> EvalContextExt<'mir, 'tcx> for MiriEvalContext<'mir, 'tcx> {}
443 pub trait EvalContextExt<'mir, 'tcx: 'mir>: MiriEvalContextExt<'mir, 'tcx> {
444 /// Temporarily allow data-races to occur. This should only be used in
445 /// one of these cases:
446 /// - One of the appropriate `validate_atomic` functions will be called to
447 /// to treat a memory access as atomic.
448 /// - The memory being accessed should be treated as internal state, that
449 /// cannot be accessed by the interpreted program.
450 /// - Execution of the interpreted program execution has halted.
452 fn allow_data_races_ref<R>(&self, op: impl FnOnce(&MiriEvalContext<'mir, 'tcx>) -> R) -> R {
453 let this = self.eval_context_ref();
454 if let Some(data_race) = &this.machine.data_race {
455 data_race.ongoing_action_data_race_free.set(true);
457 let result = op(this);
458 if let Some(data_race) = &this.machine.data_race {
459 data_race.ongoing_action_data_race_free.set(false);
464 /// Same as `allow_data_races_ref`, this temporarily disables any data-race detection and
465 /// so should only be used for atomic operations or internal state that the program cannot
468 fn allow_data_races_mut<R>(
470 op: impl FnOnce(&mut MiriEvalContext<'mir, 'tcx>) -> R,
472 let this = self.eval_context_mut();
473 if let Some(data_race) = &this.machine.data_race {
474 data_race.ongoing_action_data_race_free.set(true);
476 let result = op(this);
477 if let Some(data_race) = &this.machine.data_race {
478 data_race.ongoing_action_data_race_free.set(false);
483 /// Atomic variant of read_scalar_at_offset.
484 fn read_scalar_at_offset_atomic(
486 op: &OpTy<'tcx, Tag>,
488 layout: TyAndLayout<'tcx>,
489 atomic: AtomicReadOp,
490 ) -> InterpResult<'tcx, ScalarMaybeUninit<Tag>> {
491 let this = self.eval_context_ref();
492 let value_place = this.deref_operand_and_offset(op, offset, layout)?;
493 this.read_scalar_atomic(&value_place, atomic)
496 /// Atomic variant of write_scalar_at_offset.
497 fn write_scalar_at_offset_atomic(
499 op: &OpTy<'tcx, Tag>,
501 value: impl Into<ScalarMaybeUninit<Tag>>,
502 layout: TyAndLayout<'tcx>,
503 atomic: AtomicWriteOp,
504 ) -> InterpResult<'tcx> {
505 let this = self.eval_context_mut();
506 let value_place = this.deref_operand_and_offset(op, offset, layout)?;
507 this.write_scalar_atomic(value.into(), &value_place, atomic)
510 /// Perform an atomic read operation at the memory location.
511 fn read_scalar_atomic(
513 place: &MPlaceTy<'tcx, Tag>,
514 atomic: AtomicReadOp,
515 ) -> InterpResult<'tcx, ScalarMaybeUninit<Tag>> {
516 let this = self.eval_context_ref();
517 // This will read from the last store in the modification order of this location. In case
518 // weak memory emulation is enabled, this may not be the store we will pick to actually read from and return.
519 // This is fine with StackedBorrow and race checks because they don't concern metadata on
520 // the *value* (including the associated provenance if this is an AtomicPtr) at this location.
521 // Only metadata on the location itself is used.
522 let scalar = this.allow_data_races_ref(move |this| this.read_scalar(&place.into()))?;
523 this.validate_overlapping_atomic(place)?;
524 this.buffered_atomic_read(place, atomic, scalar, || {
525 this.validate_atomic_load(place, atomic)
529 /// Perform an atomic write operation at the memory location.
530 fn write_scalar_atomic(
532 val: ScalarMaybeUninit<Tag>,
533 dest: &MPlaceTy<'tcx, Tag>,
534 atomic: AtomicWriteOp,
535 ) -> InterpResult<'tcx> {
536 let this = self.eval_context_mut();
537 this.validate_overlapping_atomic(dest)?;
538 this.allow_data_races_mut(move |this| this.write_scalar(val, &(*dest).into()))?;
539 this.validate_atomic_store(dest, atomic)?;
540 // FIXME: it's not possible to get the value before write_scalar. A read_scalar will cause
541 // side effects from a read the program did not perform. So we have to initialise
542 // the store buffer with the value currently being written
543 // ONCE this is fixed please remove the hack in buffered_atomic_write() in weak_memory.rs
544 // https://github.com/rust-lang/miri/issues/2164
545 this.buffered_atomic_write(val, dest, atomic, val)
548 /// Perform an atomic operation on a memory location.
549 fn atomic_op_immediate(
551 place: &MPlaceTy<'tcx, Tag>,
552 rhs: &ImmTy<'tcx, Tag>,
556 ) -> InterpResult<'tcx, ImmTy<'tcx, Tag>> {
557 let this = self.eval_context_mut();
559 this.validate_overlapping_atomic(place)?;
560 let old = this.allow_data_races_mut(|this| this.read_immediate(&place.into()))?;
562 // Atomics wrap around on overflow.
563 let val = this.binary_op(op, &old, rhs)?;
564 let val = if neg { this.unary_op(mir::UnOp::Not, &val)? } else { val };
565 this.allow_data_races_mut(|this| this.write_immediate(*val, &(*place).into()))?;
567 this.validate_atomic_rmw(place, atomic)?;
569 this.buffered_atomic_rmw(
570 val.to_scalar_or_uninit(),
573 old.to_scalar_or_uninit(),
578 /// Perform an atomic exchange with a memory place and a new
579 /// scalar value, the old value is returned.
580 fn atomic_exchange_scalar(
582 place: &MPlaceTy<'tcx, Tag>,
583 new: ScalarMaybeUninit<Tag>,
585 ) -> InterpResult<'tcx, ScalarMaybeUninit<Tag>> {
586 let this = self.eval_context_mut();
588 this.validate_overlapping_atomic(place)?;
589 let old = this.allow_data_races_mut(|this| this.read_scalar(&place.into()))?;
590 this.allow_data_races_mut(|this| this.write_scalar(new, &(*place).into()))?;
592 this.validate_atomic_rmw(place, atomic)?;
594 this.buffered_atomic_rmw(new, place, atomic, old)?;
598 /// Perform an conditional atomic exchange with a memory place and a new
599 /// scalar value, the old value is returned.
600 fn atomic_min_max_scalar(
602 place: &MPlaceTy<'tcx, Tag>,
603 rhs: ImmTy<'tcx, Tag>,
606 ) -> InterpResult<'tcx, ImmTy<'tcx, Tag>> {
607 let this = self.eval_context_mut();
609 this.validate_overlapping_atomic(place)?;
610 let old = this.allow_data_races_mut(|this| this.read_immediate(&place.into()))?;
611 let lt = this.binary_op(mir::BinOp::Lt, &old, &rhs)?.to_scalar()?.to_bool()?;
613 let new_val = if min {
614 if lt { &old } else { &rhs }
616 if lt { &rhs } else { &old }
619 this.allow_data_races_mut(|this| this.write_immediate(**new_val, &(*place).into()))?;
621 this.validate_atomic_rmw(place, atomic)?;
623 this.buffered_atomic_rmw(
624 new_val.to_scalar_or_uninit(),
627 old.to_scalar_or_uninit(),
630 // Return the old value.
634 /// Perform an atomic compare and exchange at a given memory location.
635 /// On success an atomic RMW operation is performed and on failure
636 /// only an atomic read occurs. If `can_fail_spuriously` is true,
637 /// then we treat it as a "compare_exchange_weak" operation, and
638 /// some portion of the time fail even when the values are actually
640 fn atomic_compare_exchange_scalar(
642 place: &MPlaceTy<'tcx, Tag>,
643 expect_old: &ImmTy<'tcx, Tag>,
644 new: ScalarMaybeUninit<Tag>,
647 can_fail_spuriously: bool,
648 ) -> InterpResult<'tcx, Immediate<Tag>> {
650 let this = self.eval_context_mut();
652 this.validate_overlapping_atomic(place)?;
653 // Failure ordering cannot be stronger than success ordering, therefore first attempt
654 // to read with the failure ordering and if successful then try again with the success
655 // read ordering and write in the success case.
656 // Read as immediate for the sake of `binary_op()`
657 let old = this.allow_data_races_mut(|this| this.read_immediate(&(place.into())))?;
658 // `binary_op` will bail if either of them is not a scalar.
659 let eq = this.binary_op(mir::BinOp::Eq, &old, expect_old)?;
660 // If the operation would succeed, but is "weak", fail some portion
661 // of the time, based on `success_rate`.
662 let success_rate = 1.0 - this.machine.cmpxchg_weak_failure_rate;
663 let cmpxchg_success = eq.to_scalar()?.to_bool()?
664 && if can_fail_spuriously {
665 this.machine.rng.get_mut().gen_bool(success_rate)
669 let res = Immediate::ScalarPair(
670 old.to_scalar_or_uninit(),
671 Scalar::from_bool(cmpxchg_success).into(),
674 // Update ptr depending on comparison.
675 // if successful, perform a full rw-atomic validation
676 // otherwise treat this as an atomic load with the fail ordering.
678 this.allow_data_races_mut(|this| this.write_scalar(new, &(*place).into()))?;
679 this.validate_atomic_rmw(place, success)?;
680 this.buffered_atomic_rmw(new, place, success, old.to_scalar_or_uninit())?;
682 this.validate_atomic_load(place, fail)?;
683 // A failed compare exchange is equivalent to a load, reading from the latest store
684 // in the modification order.
685 // Since `old` is only a value and not the store element, we need to separately
686 // find it in our store buffer and perform load_impl on it.
687 this.perform_read_on_buffered_latest(place, fail, old.to_scalar_or_uninit())?;
690 // Return the old value.
694 /// Update the data-race detector for an atomic read occurring at the
695 /// associated memory-place and on the current thread.
696 fn validate_atomic_load(
698 place: &MPlaceTy<'tcx, Tag>,
699 atomic: AtomicReadOp,
700 ) -> InterpResult<'tcx> {
701 let this = self.eval_context_ref();
702 this.validate_overlapping_atomic(place)?;
703 this.validate_atomic_op(
707 move |memory, clocks, index, atomic| {
708 if atomic == AtomicReadOp::Relaxed {
709 memory.load_relaxed(&mut *clocks, index)
711 memory.load_acquire(&mut *clocks, index)
717 /// Update the data-race detector for an atomic write occurring at the
718 /// associated memory-place and on the current thread.
719 fn validate_atomic_store(
721 place: &MPlaceTy<'tcx, Tag>,
722 atomic: AtomicWriteOp,
723 ) -> InterpResult<'tcx> {
724 let this = self.eval_context_mut();
725 this.validate_overlapping_atomic(place)?;
726 this.validate_atomic_op(
730 move |memory, clocks, index, atomic| {
731 if atomic == AtomicWriteOp::Relaxed {
732 memory.store_relaxed(clocks, index)
734 memory.store_release(clocks, index)
740 /// Update the data-race detector for an atomic read-modify-write occurring
741 /// at the associated memory place and on the current thread.
742 fn validate_atomic_rmw(
744 place: &MPlaceTy<'tcx, Tag>,
746 ) -> InterpResult<'tcx> {
748 let acquire = matches!(atomic, Acquire | AcqRel | SeqCst);
749 let release = matches!(atomic, Release | AcqRel | SeqCst);
750 let this = self.eval_context_mut();
751 this.validate_overlapping_atomic(place)?;
752 this.validate_atomic_op(place, atomic, "Atomic RMW", move |memory, clocks, index, _| {
754 memory.load_acquire(clocks, index)?;
756 memory.load_relaxed(clocks, index)?;
759 memory.rmw_release(clocks, index)
761 memory.rmw_relaxed(clocks, index)
766 /// Update the data-race detector for an atomic fence on the current thread.
767 fn validate_atomic_fence(&mut self, atomic: AtomicFenceOp) -> InterpResult<'tcx> {
768 let this = self.eval_context_mut();
769 if let Some(data_race) = &mut this.machine.data_race {
770 data_race.maybe_perform_sync_operation(|index, mut clocks| {
771 log::trace!("Atomic fence on {:?} with ordering {:?}", index, atomic);
773 // Apply data-race detection for the current fences
774 // this treats AcqRel and SeqCst as the same as an acquire
775 // and release fence applied in the same timestamp.
776 if atomic != AtomicFenceOp::Release {
777 // Either Acquire | AcqRel | SeqCst
778 clocks.apply_acquire_fence();
780 if atomic != AtomicFenceOp::Acquire {
781 // Either Release | AcqRel | SeqCst
782 clocks.apply_release_fence();
784 if atomic == AtomicFenceOp::SeqCst {
785 data_race.last_sc_fence.borrow_mut().set_at_index(&clocks.clock, index);
786 clocks.fence_seqcst.join(&data_race.last_sc_fence.borrow());
787 clocks.write_seqcst.join(&data_race.last_sc_write.borrow());
790 // Increment timestamp in case of release semantics.
791 Ok(atomic != AtomicFenceOp::Acquire)
799 /// Vector clock metadata for a logical memory allocation.
800 #[derive(Debug, Clone)]
801 pub struct VClockAlloc {
802 /// Assigning each byte a MemoryCellClocks.
803 alloc_ranges: RefCell<RangeMap<MemoryCellClocks>>,
807 /// Create a new data-race detector for newly allocated memory.
808 pub fn new_allocation(
809 global: &GlobalState,
811 kind: MemoryKind<MiriMemoryKind>,
813 let (alloc_timestamp, alloc_index) = match kind {
814 // User allocated and stack memory should track allocation.
816 MiriMemoryKind::Rust | MiriMemoryKind::C | MiriMemoryKind::WinHeap,
818 | MemoryKind::Stack => {
819 let (alloc_index, clocks) = global.current_thread_state();
820 let alloc_timestamp = clocks.clock[alloc_index];
821 (alloc_timestamp, alloc_index)
823 // Other global memory should trace races but be allocated at the 0 timestamp.
825 MiriMemoryKind::Global
826 | MiriMemoryKind::Machine
827 | MiriMemoryKind::Runtime
828 | MiriMemoryKind::ExternStatic
829 | MiriMemoryKind::Tls,
831 | MemoryKind::CallerLocation => (0, VectorIdx::MAX_INDEX),
834 alloc_ranges: RefCell::new(RangeMap::new(
836 MemoryCellClocks::new(alloc_timestamp, alloc_index),
841 // Find an index, if one exists where the value
842 // in `l` is greater than the value in `r`.
843 fn find_gt_index(l: &VClock, r: &VClock) -> Option<VectorIdx> {
844 log::trace!("Find index where not {:?} <= {:?}", l, r);
845 let l_slice = l.as_slice();
846 let r_slice = r.as_slice();
851 .find_map(|(idx, (&l, &r))| if l > r { Some(idx) } else { None })
853 if l_slice.len() > r_slice.len() {
854 // By invariant, if l_slice is longer
855 // then one element must be larger.
856 // This just validates that this is true
857 // and reports earlier elements first.
858 let l_remainder_slice = &l_slice[r_slice.len()..];
859 let idx = l_remainder_slice
862 .find_map(|(idx, &r)| if r == 0 { None } else { Some(idx) })
863 .expect("Invalid VClock Invariant");
864 Some(idx + r_slice.len())
872 /// Report a data-race found in the program.
873 /// This finds the two racing threads and the type
874 /// of data-race that occurred. This will also
875 /// return info about the memory location the data-race
879 fn report_data_race<'tcx>(
880 global: &GlobalState,
881 range: &MemoryCellClocks,
884 ptr_dbg: Pointer<AllocId>,
885 ) -> InterpResult<'tcx> {
886 let (current_index, current_clocks) = global.current_thread_state();
888 let (other_action, other_thread, other_clock) = if range.write
889 > current_clocks.clock[range.write_index]
891 // Convert the write action into the vector clock it
892 // represents for diagnostic purposes.
893 write_clock = VClock::new_with_index(range.write_index, range.write);
894 (range.write_type.get_descriptor(), range.write_index, &write_clock)
895 } else if let Some(idx) = Self::find_gt_index(&range.read, ¤t_clocks.clock) {
896 ("Read", idx, &range.read)
897 } else if !is_atomic {
898 if let Some(atomic) = range.atomic() {
899 if let Some(idx) = Self::find_gt_index(&atomic.write_vector, ¤t_clocks.clock)
901 ("Atomic Store", idx, &atomic.write_vector)
902 } else if let Some(idx) =
903 Self::find_gt_index(&atomic.read_vector, ¤t_clocks.clock)
905 ("Atomic Load", idx, &atomic.read_vector)
908 "Failed to report data-race for non-atomic operation: no race found"
913 "Failed to report data-race for non-atomic operation: no atomic component"
917 unreachable!("Failed to report data-race for atomic operation")
920 // Load elaborated thread information about the racing thread actions.
921 let current_thread_info = global.print_thread_metadata(current_index);
922 let other_thread_info = global.print_thread_metadata(other_thread);
924 // Throw the data-race detection.
926 "Data race detected between {} on {} and {} on {} at {:?} (current vector clock = {:?}, conflicting timestamp = {:?})",
932 current_clocks.clock,
937 /// Detect racing atomic read and writes (not data races)
938 /// on every byte of the current access range
939 pub(super) fn race_free_with_atomic(&self, range: AllocRange, global: &GlobalState) -> bool {
940 if global.race_detecting() {
941 let (_, clocks) = global.current_thread_state();
942 let alloc_ranges = self.alloc_ranges.borrow();
943 for (_, range) in alloc_ranges.iter(range.start, range.size) {
944 if !range.race_free_with_atomic(&clocks) {
952 /// Detect data-races for an unsynchronized read operation, will not perform
953 /// data-race detection if `race_detecting()` is false, either due to no threads
954 /// being created or if it is temporarily disabled during a racy read or write
955 /// operation for which data-race detection is handled separately, for example
956 /// atomic read operations.
961 global: &GlobalState,
962 ) -> InterpResult<'tcx> {
963 if global.race_detecting() {
964 let (index, clocks) = global.current_thread_state();
965 let mut alloc_ranges = self.alloc_ranges.borrow_mut();
966 for (offset, range) in alloc_ranges.iter_mut(range.start, range.size) {
967 if let Err(DataRace) = range.read_race_detect(&*clocks, index) {
969 return Self::report_data_race(
974 Pointer::new(alloc_id, offset),
984 // Shared code for detecting data-races on unique access to a section of memory
985 fn unique_access<'tcx>(
989 write_type: WriteType,
990 global: &mut GlobalState,
991 ) -> InterpResult<'tcx> {
992 if global.race_detecting() {
993 let (index, clocks) = global.current_thread_state();
994 for (offset, range) in self.alloc_ranges.get_mut().iter_mut(range.start, range.size) {
995 if let Err(DataRace) = range.write_race_detect(&*clocks, index, write_type) {
997 return Self::report_data_race(
1000 write_type.get_descriptor(),
1002 Pointer::new(alloc_id, offset),
1012 /// Detect data-races for an unsynchronized write operation, will not perform
1013 /// data-race threads if `race_detecting()` is false, either due to no threads
1014 /// being created or if it is temporarily disabled during a racy read or write
1020 global: &mut GlobalState,
1021 ) -> InterpResult<'tcx> {
1022 self.unique_access(alloc_id, range, WriteType::Write, global)
1025 /// Detect data-races for an unsynchronized deallocate operation, will not perform
1026 /// data-race threads if `race_detecting()` is false, either due to no threads
1027 /// being created or if it is temporarily disabled during a racy read or write
1029 pub fn deallocate<'tcx>(
1033 global: &mut GlobalState,
1034 ) -> InterpResult<'tcx> {
1035 self.unique_access(alloc_id, range, WriteType::Deallocate, global)
1039 impl<'mir, 'tcx: 'mir> EvalContextPrivExt<'mir, 'tcx> for MiriEvalContext<'mir, 'tcx> {}
1040 trait EvalContextPrivExt<'mir, 'tcx: 'mir>: MiriEvalContextExt<'mir, 'tcx> {
1041 /// Generic atomic operation implementation
1042 fn validate_atomic_op<A: Debug + Copy>(
1044 place: &MPlaceTy<'tcx, Tag>,
1048 &mut MemoryCellClocks,
1049 &mut ThreadClockSet,
1052 ) -> Result<(), DataRace>,
1053 ) -> InterpResult<'tcx> {
1054 let this = self.eval_context_ref();
1055 if let Some(data_race) = &this.machine.data_race {
1056 if data_race.race_detecting() {
1057 let size = place.layout.size;
1058 let (alloc_id, base_offset, _tag) = this.ptr_get_alloc_id(place.ptr)?;
1059 // Load and log the atomic operation.
1060 // Note that atomic loads are possible even from read-only allocations, so `get_alloc_extra_mut` is not an option.
1061 let alloc_meta = this.get_alloc_extra(alloc_id)?.data_race.as_ref().unwrap();
1063 "Atomic op({}) with ordering {:?} on {:?} (size={})",
1070 // Perform the atomic operation.
1071 data_race.maybe_perform_sync_operation(|index, mut clocks| {
1072 for (offset, range) in
1073 alloc_meta.alloc_ranges.borrow_mut().iter_mut(base_offset, size)
1075 if let Err(DataRace) = op(range, &mut *clocks, index, atomic) {
1077 return VClockAlloc::report_data_race(
1082 Pointer::new(alloc_id, offset),
1088 // This conservatively assumes all operations have release semantics
1092 // Log changes to atomic memory.
1093 if log::log_enabled!(log::Level::Trace) {
1094 for (_offset, range) in alloc_meta.alloc_ranges.borrow().iter(base_offset, size)
1097 "Updated atomic memory({:?}, size={}) to {:#?}",
1110 /// Extra metadata associated with a thread.
1111 #[derive(Debug, Clone, Default)]
1112 struct ThreadExtraState {
1113 /// The current vector index in use by the
1114 /// thread currently, this is set to None
1115 /// after the vector index has been re-used
1116 /// and hence the value will never need to be
1117 /// read during data-race reporting.
1118 vector_index: Option<VectorIdx>,
1120 /// The name of the thread, updated for better
1121 /// diagnostics when reporting detected data
1123 thread_name: Option<Box<str>>,
1125 /// Thread termination vector clock, this
1126 /// is set on thread termination and is used
1127 /// for joining on threads since the vector_index
1128 /// may be re-used when the join operation occurs.
1129 termination_vector_clock: Option<VClock>,
1132 /// Global data-race detection state, contains the currently
1133 /// executing thread as well as the vector-clocks associated
1134 /// with each of the threads.
1135 // FIXME: it is probably better to have one large RefCell, than to have so many small ones.
1136 #[derive(Debug, Clone)]
1137 pub struct GlobalState {
1138 /// Set to true once the first additional
1139 /// thread has launched, due to the dependency
1140 /// between before and after a thread launch.
1141 /// Any data-races must be recorded after this
1142 /// so concurrent execution can ignore recording
1144 multi_threaded: Cell<bool>,
1146 /// A flag to mark we are currently performing
1147 /// a data race free action (such as atomic access)
1148 /// to supress the race detector
1149 ongoing_action_data_race_free: Cell<bool>,
1151 /// Mapping of a vector index to a known set of thread
1152 /// clocks, this is not directly mapping from a thread id
1153 /// since it may refer to multiple threads.
1154 vector_clocks: RefCell<IndexVec<VectorIdx, ThreadClockSet>>,
1156 /// Mapping of a given vector index to the current thread
1157 /// that the execution is representing, this may change
1158 /// if a vector index is re-assigned to a new thread.
1159 vector_info: RefCell<IndexVec<VectorIdx, ThreadId>>,
1161 /// The mapping of a given thread to associated thread metadata.
1162 thread_info: RefCell<IndexVec<ThreadId, ThreadExtraState>>,
1164 /// The current vector index being executed.
1165 current_index: Cell<VectorIdx>,
1167 /// Potential vector indices that could be re-used on thread creation
1168 /// values are inserted here on after the thread has terminated and
1169 /// been joined with, and hence may potentially become free
1170 /// for use as the index for a new thread.
1171 /// Elements in this set may still require the vector index to
1172 /// report data-races, and can only be re-used after all
1173 /// active vector-clocks catch up with the threads timestamp.
1174 reuse_candidates: RefCell<FxHashSet<VectorIdx>>,
1176 /// Counts the number of threads that are currently active
1177 /// if the number of active threads reduces to 1 and then
1178 /// a join operation occurs with the remaining main thread
1179 /// then multi-threaded execution may be disabled.
1180 active_thread_count: Cell<usize>,
1182 /// This contains threads that have terminated, but not yet joined
1183 /// and so cannot become re-use candidates until a join operation
1185 /// The associated vector index will be moved into re-use candidates
1186 /// after the join operation occurs.
1187 terminated_threads: RefCell<FxHashMap<ThreadId, VectorIdx>>,
1189 /// The timestamp of last SC fence performed by each thread
1190 last_sc_fence: RefCell<VClock>,
1192 /// The timestamp of last SC write performed by each thread
1193 last_sc_write: RefCell<VClock>,
1197 /// Create a new global state, setup with just thread-id=0
1198 /// advanced to timestamp = 1.
1199 pub fn new() -> Self {
1200 let mut global_state = GlobalState {
1201 multi_threaded: Cell::new(false),
1202 ongoing_action_data_race_free: Cell::new(false),
1203 vector_clocks: RefCell::new(IndexVec::new()),
1204 vector_info: RefCell::new(IndexVec::new()),
1205 thread_info: RefCell::new(IndexVec::new()),
1206 current_index: Cell::new(VectorIdx::new(0)),
1207 active_thread_count: Cell::new(1),
1208 reuse_candidates: RefCell::new(FxHashSet::default()),
1209 terminated_threads: RefCell::new(FxHashMap::default()),
1210 last_sc_fence: RefCell::new(VClock::default()),
1211 last_sc_write: RefCell::new(VClock::default()),
1214 // Setup the main-thread since it is not explicitly created:
1215 // uses vector index and thread-id 0, also the rust runtime gives
1216 // the main-thread a name of "main".
1217 let index = global_state.vector_clocks.get_mut().push(ThreadClockSet::default());
1218 global_state.vector_info.get_mut().push(ThreadId::new(0));
1219 global_state.thread_info.get_mut().push(ThreadExtraState {
1220 vector_index: Some(index),
1221 thread_name: Some("main".to_string().into_boxed_str()),
1222 termination_vector_clock: None,
1228 // We perform data race detection when there are more than 1 active thread
1229 // and we have not temporarily disabled race detection to perform something
1231 fn race_detecting(&self) -> bool {
1232 self.multi_threaded.get() && !self.ongoing_action_data_race_free.get()
1235 pub fn ongoing_action_data_race_free(&self) -> bool {
1236 self.ongoing_action_data_race_free.get()
1239 // Try to find vector index values that can potentially be re-used
1240 // by a new thread instead of a new vector index being created.
1241 fn find_vector_index_reuse_candidate(&self) -> Option<VectorIdx> {
1242 let mut reuse = self.reuse_candidates.borrow_mut();
1243 let vector_clocks = self.vector_clocks.borrow();
1244 let vector_info = self.vector_info.borrow();
1245 let terminated_threads = self.terminated_threads.borrow();
1246 for &candidate in reuse.iter() {
1247 let target_timestamp = vector_clocks[candidate].clock[candidate];
1248 if vector_clocks.iter_enumerated().all(|(clock_idx, clock)| {
1249 // The thread happens before the clock, and hence cannot report
1250 // a data-race with this the candidate index.
1251 let no_data_race = clock.clock[candidate] >= target_timestamp;
1253 // The vector represents a thread that has terminated and hence cannot
1254 // report a data-race with the candidate index.
1255 let thread_id = vector_info[clock_idx];
1256 let vector_terminated =
1257 reuse.contains(&clock_idx) || terminated_threads.contains_key(&thread_id);
1259 // The vector index cannot report a race with the candidate index
1260 // and hence allows the candidate index to be re-used.
1261 no_data_race || vector_terminated
1263 // All vector clocks for each vector index are equal to
1264 // the target timestamp, and the thread is known to have
1265 // terminated, therefore this vector clock index cannot
1266 // report any more data-races.
1267 assert!(reuse.remove(&candidate));
1268 return Some(candidate);
1274 // Hook for thread creation, enabled multi-threaded execution and marks
1275 // the current thread timestamp as happening-before the current thread.
1277 pub fn thread_created(&mut self, thread: ThreadId) {
1278 let current_index = self.current_index();
1280 // Increment the number of active threads.
1281 let active_threads = self.active_thread_count.get();
1282 self.active_thread_count.set(active_threads + 1);
1284 // Enable multi-threaded execution, there are now two threads
1285 // so data-races are now possible.
1286 self.multi_threaded.set(true);
1288 // Load and setup the associated thread metadata
1289 let mut thread_info = self.thread_info.borrow_mut();
1290 thread_info.ensure_contains_elem(thread, Default::default);
1292 // Assign a vector index for the thread, attempting to re-use an old
1293 // vector index that can no longer report any data-races if possible.
1294 let created_index = if let Some(reuse_index) = self.find_vector_index_reuse_candidate() {
1295 // Now re-configure the re-use candidate, increment the clock
1296 // for the new sync use of the vector.
1297 let vector_clocks = self.vector_clocks.get_mut();
1298 vector_clocks[reuse_index].increment_clock(reuse_index);
1300 // Locate the old thread the vector was associated with and update
1301 // it to represent the new thread instead.
1302 let vector_info = self.vector_info.get_mut();
1303 let old_thread = vector_info[reuse_index];
1304 vector_info[reuse_index] = thread;
1306 // Mark the thread the vector index was associated with as no longer
1307 // representing a thread index.
1308 thread_info[old_thread].vector_index = None;
1312 // No vector re-use candidates available, instead create
1313 // a new vector index.
1314 let vector_info = self.vector_info.get_mut();
1315 vector_info.push(thread)
1318 log::trace!("Creating thread = {:?} with vector index = {:?}", thread, created_index);
1320 // Mark the chosen vector index as in use by the thread.
1321 thread_info[thread].vector_index = Some(created_index);
1323 // Create a thread clock set if applicable.
1324 let vector_clocks = self.vector_clocks.get_mut();
1325 if created_index == vector_clocks.next_index() {
1326 vector_clocks.push(ThreadClockSet::default());
1329 // Now load the two clocks and configure the initial state.
1330 let (current, created) = vector_clocks.pick2_mut(current_index, created_index);
1332 // Join the created with current, since the current threads
1333 // previous actions happen-before the created thread.
1334 created.join_with(current);
1336 // Advance both threads after the synchronized operation.
1337 // Both operations are considered to have release semantics.
1338 current.increment_clock(current_index);
1339 created.increment_clock(created_index);
1342 /// Hook on a thread join to update the implicit happens-before relation
1343 /// between the joined thread and the current thread.
1345 pub fn thread_joined(&mut self, current_thread: ThreadId, join_thread: ThreadId) {
1346 let clocks_vec = self.vector_clocks.get_mut();
1347 let thread_info = self.thread_info.get_mut();
1349 // Load the vector clock of the current thread.
1350 let current_index = thread_info[current_thread]
1352 .expect("Performed thread join on thread with no assigned vector");
1353 let current = &mut clocks_vec[current_index];
1355 // Load the associated vector clock for the terminated thread.
1356 let join_clock = thread_info[join_thread]
1357 .termination_vector_clock
1359 .expect("Joined with thread but thread has not terminated");
1361 // The join thread happens-before the current thread
1362 // so update the current vector clock.
1363 // Is not a release operation so the clock is not incremented.
1364 current.clock.join(join_clock);
1366 // Check the number of active threads, if the value is 1
1367 // then test for potentially disabling multi-threaded execution.
1368 let active_threads = self.active_thread_count.get();
1369 if active_threads == 1 {
1370 // May potentially be able to disable multi-threaded execution.
1371 let current_clock = &clocks_vec[current_index];
1374 .all(|(idx, clocks)| clocks.clock[idx] <= current_clock.clock[idx])
1376 // All thread terminations happen-before the current clock
1377 // therefore no data-races can be reported until a new thread
1378 // is created, so disable multi-threaded execution.
1379 self.multi_threaded.set(false);
1383 // If the thread is marked as terminated but not joined
1384 // then move the thread to the re-use set.
1385 let termination = self.terminated_threads.get_mut();
1386 if let Some(index) = termination.remove(&join_thread) {
1387 let reuse = self.reuse_candidates.get_mut();
1388 reuse.insert(index);
1392 /// On thread termination, the vector-clock may re-used
1393 /// in the future once all remaining thread-clocks catch
1394 /// up with the time index of the terminated thread.
1395 /// This assigns thread termination with a unique index
1396 /// which will be used to join the thread
1397 /// This should be called strictly before any calls to
1398 /// `thread_joined`.
1400 pub fn thread_terminated(&mut self) {
1401 let current_index = self.current_index();
1403 // Increment the clock to a unique termination timestamp.
1404 let vector_clocks = self.vector_clocks.get_mut();
1405 let current_clocks = &mut vector_clocks[current_index];
1406 current_clocks.increment_clock(current_index);
1408 // Load the current thread id for the executing vector.
1409 let vector_info = self.vector_info.get_mut();
1410 let current_thread = vector_info[current_index];
1412 // Load the current thread metadata, and move to a terminated
1413 // vector state. Setting up the vector clock all join operations
1415 let thread_info = self.thread_info.get_mut();
1416 let current = &mut thread_info[current_thread];
1417 current.termination_vector_clock = Some(current_clocks.clock.clone());
1419 // Add this thread as a candidate for re-use after a thread join
1421 let termination = self.terminated_threads.get_mut();
1422 termination.insert(current_thread, current_index);
1424 // Reduce the number of active threads, now that a thread has
1426 let mut active_threads = self.active_thread_count.get();
1427 active_threads -= 1;
1428 self.active_thread_count.set(active_threads);
1431 /// Hook for updating the local tracker of the currently
1432 /// enabled thread, should always be updated whenever
1433 /// `active_thread` in thread.rs is updated.
1435 pub fn thread_set_active(&self, thread: ThreadId) {
1436 let thread_info = self.thread_info.borrow();
1437 let vector_idx = thread_info[thread]
1439 .expect("Setting thread active with no assigned vector");
1440 self.current_index.set(vector_idx);
1443 /// Hook for updating the local tracker of the threads name
1444 /// this should always mirror the local value in thread.rs
1445 /// the thread name is used for improved diagnostics
1446 /// during a data-race.
1448 pub fn thread_set_name(&mut self, thread: ThreadId, name: String) {
1449 let name = name.into_boxed_str();
1450 let thread_info = self.thread_info.get_mut();
1451 thread_info[thread].thread_name = Some(name);
1454 /// Attempt to perform a synchronized operation, this
1455 /// will perform no operation if multi-threading is
1456 /// not currently enabled.
1457 /// Otherwise it will increment the clock for the current
1458 /// vector before and after the operation for data-race
1459 /// detection between any happens-before edges the
1460 /// operation may create.
1461 fn maybe_perform_sync_operation<'tcx>(
1463 op: impl FnOnce(VectorIdx, RefMut<'_, ThreadClockSet>) -> InterpResult<'tcx, bool>,
1464 ) -> InterpResult<'tcx> {
1465 if self.multi_threaded.get() {
1466 let (index, clocks) = self.current_thread_state_mut();
1467 if op(index, clocks)? {
1468 let (_, mut clocks) = self.current_thread_state_mut();
1469 clocks.increment_clock(index);
1475 /// Internal utility to identify a thread stored internally
1476 /// returns the id and the name for better diagnostics.
1477 fn print_thread_metadata(&self, vector: VectorIdx) -> String {
1478 let thread = self.vector_info.borrow()[vector];
1479 let thread_name = &self.thread_info.borrow()[thread].thread_name;
1480 if let Some(name) = thread_name {
1481 let name: &str = name;
1482 format!("Thread(id = {:?}, name = {:?})", thread.to_u32(), name)
1484 format!("Thread(id = {:?})", thread.to_u32())
1488 /// Acquire a lock, express that the previous call of
1489 /// `validate_lock_release` must happen before this.
1490 /// As this is an acquire operation, the thread timestamp is not
1492 pub fn validate_lock_acquire(&self, lock: &VClock, thread: ThreadId) {
1493 let (_, mut clocks) = self.load_thread_state_mut(thread);
1494 clocks.clock.join(lock);
1497 /// Release a lock handle, express that this happens-before
1498 /// any subsequent calls to `validate_lock_acquire`.
1499 /// For normal locks this should be equivalent to `validate_lock_release_shared`
1500 /// since an acquire operation should have occurred before, however
1501 /// for futex & condvar operations this is not the case and this
1502 /// operation must be used.
1503 pub fn validate_lock_release(&self, lock: &mut VClock, thread: ThreadId) {
1504 let (index, mut clocks) = self.load_thread_state_mut(thread);
1505 lock.clone_from(&clocks.clock);
1506 clocks.increment_clock(index);
1509 /// Release a lock handle, express that this happens-before
1510 /// any subsequent calls to `validate_lock_acquire` as well
1511 /// as any previous calls to this function after any
1512 /// `validate_lock_release` calls.
1513 /// For normal locks this should be equivalent to `validate_lock_release`.
1514 /// This function only exists for joining over the set of concurrent readers
1515 /// in a read-write lock and should not be used for anything else.
1516 pub fn validate_lock_release_shared(&self, lock: &mut VClock, thread: ThreadId) {
1517 let (index, mut clocks) = self.load_thread_state_mut(thread);
1518 lock.join(&clocks.clock);
1519 clocks.increment_clock(index);
1522 /// Load the vector index used by the given thread as well as the set of vector clocks
1523 /// used by the thread.
1525 fn load_thread_state_mut(&self, thread: ThreadId) -> (VectorIdx, RefMut<'_, ThreadClockSet>) {
1526 let index = self.thread_info.borrow()[thread]
1528 .expect("Loading thread state for thread with no assigned vector");
1529 let ref_vector = self.vector_clocks.borrow_mut();
1530 let clocks = RefMut::map(ref_vector, |vec| &mut vec[index]);
1534 /// Load the current vector clock in use and the current set of thread clocks
1535 /// in use for the vector.
1537 pub(super) fn current_thread_state(&self) -> (VectorIdx, Ref<'_, ThreadClockSet>) {
1538 let index = self.current_index();
1539 let ref_vector = self.vector_clocks.borrow();
1540 let clocks = Ref::map(ref_vector, |vec| &vec[index]);
1544 /// Load the current vector clock in use and the current set of thread clocks
1545 /// in use for the vector mutably for modification.
1547 pub(super) fn current_thread_state_mut(&self) -> (VectorIdx, RefMut<'_, ThreadClockSet>) {
1548 let index = self.current_index();
1549 let ref_vector = self.vector_clocks.borrow_mut();
1550 let clocks = RefMut::map(ref_vector, |vec| &mut vec[index]);
1554 /// Return the current thread, should be the same
1555 /// as the data-race active thread.
1557 fn current_index(&self) -> VectorIdx {
1558 self.current_index.get()
1561 // SC ATOMIC STORE rule in the paper.
1562 pub(super) fn sc_write(&self) {
1563 let (index, clocks) = self.current_thread_state();
1564 self.last_sc_write.borrow_mut().set_at_index(&clocks.clock, index);
1567 // SC ATOMIC READ rule in the paper.
1568 pub(super) fn sc_read(&self) {
1569 let (.., mut clocks) = self.current_thread_state_mut();
1570 clocks.read_seqcst.join(&self.last_sc_fence.borrow());