lock_count: usize,
/// The queue of threads waiting for this mutex.
queue: VecDeque<ThreadId>,
+ /// Data race handle, this tracks the happens-before
+ /// relationship between each mutex access. It is
+ /// released to during unlock and acquired from during
+ /// locking, and therefore stores the clock of the last
+ /// thread to release this mutex.
+ data_race: VClock,
}
declare_id!(RwLockId);
writer_queue: VecDeque<ThreadId>,
/// The queue of reader threads waiting for this lock.
reader_queue: VecDeque<ThreadId>,
+ /// Data race handle for writers, tracks the happens-before
+ /// ordering between each write access to a rwlock and is updated
+ /// after a sequence of concurrent readers to track the happens-
+ /// before ordering between the set of previous readers and
+ /// the current writer.
+ /// Contains the clock of the last thread to release a writer
+ /// lock or the joined clock of the set of last threads to release
+ /// shared reader locks.
+ data_race: VClock,
+ /// Data race handle for readers, this is temporary storage
+ /// for the combined happens-before ordering for between all
+ /// concurrent readers and the next writer, and the value
+ /// is stored to the main data_race variable once all
+ /// readers are finished.
+ /// Has to be stored separately since reader lock acquires
+ /// must load the clock of the last write and must not
+ /// add happens-before orderings between shared reader
+ /// locks.
+ data_race_reader: VClock,
}
declare_id!(CondvarId);
#[derive(Default, Debug)]
struct Condvar {
waiters: VecDeque<CondvarWaiter>,
+ /// Tracks the happens-before relationship
+ /// between a cond-var signal and a cond-var
+ /// wait during a non-suprious signal event.
+ /// Contains the clock of the last thread to
+ /// perform a futex-signal.
+ data_race: VClock,
+}
+
+/// The futex state.
+#[derive(Default, Debug)]
+struct Futex {
+ waiters: VecDeque<FutexWaiter>,
+ /// Tracks the happens-before relationship
+ /// between a futex-wake and a futex-wait
+ /// during a non-spurious wake event.
+ /// Contains the clock of the last thread to
+ /// perform a futex-wake.
+ data_race: VClock,
+}
+
+/// A thread waiting on a futex.
+#[derive(Debug)]
+struct FutexWaiter {
+ /// The thread that is waiting on this futex.
+ thread: ThreadId,
}
/// The state of all synchronization variables.
mutexes: IndexVec<MutexId, Mutex>,
rwlocks: IndexVec<RwLockId, RwLock>,
condvars: IndexVec<CondvarId, Condvar>,
+ futexes: HashMap<u64, Futex>,
}
// Private extension trait for local helper methods
mutex.owner = Some(thread);
}
mutex.lock_count = mutex.lock_count.checked_add(1).unwrap();
+ if let Some(data_race) = &this.memory.extra.data_race {
+ data_race.validate_lock_acquire(&mutex.data_race, thread);
+ }
}
/// Try unlocking by decreasing the lock count and returning the old lock
/// count. If the lock count reaches 0, release the lock and potentially
/// give to a new owner. If the lock was not locked by `expected_owner`,
/// return `None`.
- fn mutex_unlock(
- &mut self,
- id: MutexId,
- expected_owner: ThreadId,
- ) -> Option<usize> {
+ fn mutex_unlock(&mut self, id: MutexId, expected_owner: ThreadId) -> Option<usize> {
let this = self.eval_context_mut();
let mutex = &mut this.machine.threads.sync.mutexes[id];
if let Some(current_owner) = mutex.owner {
mutex.owner = None;
// The mutex is completely unlocked. Try transfering ownership
// to another thread.
+ if let Some(data_race) = &this.memory.extra.data_race {
+ data_race.validate_lock_release(&mut mutex.data_race, current_owner);
+ }
this.mutex_dequeue_and_lock(id);
}
Some(old_lock_count)
let rwlock = &this.machine.threads.sync.rwlocks[id];
trace!(
"rwlock_is_locked: {:?} writer is {:?} and there are {} reader threads (some of which could hold multiple read locks)",
- id, rwlock.writer, rwlock.readers.len(),
+ id,
+ rwlock.writer,
+ rwlock.readers.len(),
);
- rwlock.writer.is_some()|| rwlock.readers.is_empty().not()
+ rwlock.writer.is_some() || rwlock.readers.is_empty().not()
}
#[inline]
let this = self.eval_context_mut();
assert!(!this.rwlock_is_write_locked(id), "the lock is write locked");
trace!("rwlock_reader_lock: {:?} now also held (one more time) by {:?}", id, reader);
- let count = this.machine.threads.sync.rwlocks[id].readers.entry(reader).or_insert(0);
+ let rwlock = &mut this.machine.threads.sync.rwlocks[id];
+ let count = rwlock.readers.entry(reader).or_insert(0);
*count = count.checked_add(1).expect("the reader counter overflowed");
+ if let Some(data_race) = &this.memory.extra.data_race {
+ data_race.validate_lock_acquire(&rwlock.data_race, reader);
+ }
}
/// Try read-unlock the lock for `reader` and potentially give the lock to a new owner.
/// Returns `true` if succeeded, `false` if this `reader` did not hold the lock.
fn rwlock_reader_unlock(&mut self, id: RwLockId, reader: ThreadId) -> bool {
let this = self.eval_context_mut();
- match this.machine.threads.sync.rwlocks[id].readers.entry(reader) {
+ let rwlock = &mut this.machine.threads.sync.rwlocks[id];
+ match rwlock.readers.entry(reader) {
Entry::Occupied(mut entry) => {
let count = entry.get_mut();
assert!(*count > 0, "rwlock locked with count == 0");
}
Entry::Vacant(_) => return false, // we did not even own this lock
}
+ if let Some(data_race) = &this.memory.extra.data_race {
+ data_race.validate_lock_release_shared(&mut rwlock.data_race_reader, reader);
+ }
+
// The thread was a reader. If the lock is not held any more, give it to a writer.
if this.rwlock_is_locked(id).not() {
+ // All the readers are finished, so set the writer data-race handle to the value
+ // of the union of all reader data race handles, since the set of readers
+ // happen-before the writers
+ let rwlock = &mut this.machine.threads.sync.rwlocks[id];
+ rwlock.data_race.clone_from(&rwlock.data_race_reader);
this.rwlock_dequeue_and_lock_writer(id);
}
true
#[inline]
/// Put the reader in the queue waiting for the lock and block it.
- fn rwlock_enqueue_and_block_reader(
- &mut self,
- id: RwLockId,
- reader: ThreadId,
- ) {
+ fn rwlock_enqueue_and_block_reader(&mut self, id: RwLockId, reader: ThreadId) {
let this = self.eval_context_mut();
assert!(this.rwlock_is_write_locked(id), "read-queueing on not write locked rwlock");
this.machine.threads.sync.rwlocks[id].reader_queue.push_back(reader);
let this = self.eval_context_mut();
assert!(!this.rwlock_is_locked(id), "the rwlock is already locked");
trace!("rwlock_writer_lock: {:?} now held by {:?}", id, writer);
- this.machine.threads.sync.rwlocks[id].writer = Some(writer);
+ let rwlock = &mut this.machine.threads.sync.rwlocks[id];
+ rwlock.writer = Some(writer);
+ if let Some(data_race) = &this.memory.extra.data_race {
+ data_race.validate_lock_acquire(&rwlock.data_race, writer);
+ }
}
#[inline]
}
rwlock.writer = None;
trace!("rwlock_writer_unlock: {:?} unlocked by {:?}", id, expected_writer);
+ // Release memory to both reader and writer vector clocks
+ // since this writer happens-before both the union of readers once they are finished
+ // and the next writer
+ if let Some(data_race) = &this.memory.extra.data_race {
+ data_race.validate_lock_release(&mut rwlock.data_race, current_writer);
+ data_race.validate_lock_release(&mut rwlock.data_race_reader, current_writer);
+ }
// The thread was a writer.
//
// We are prioritizing writers here against the readers. As a
#[inline]
/// Put the writer in the queue waiting for the lock.
- fn rwlock_enqueue_and_block_writer(
- &mut self,
- id: RwLockId,
- writer: ThreadId,
- ) {
+ fn rwlock_enqueue_and_block_writer(&mut self, id: RwLockId, writer: ThreadId) {
let this = self.eval_context_mut();
assert!(this.rwlock_is_locked(id), "write-queueing on unlocked rwlock");
this.machine.threads.sync.rwlocks[id].writer_queue.push_back(writer);
/// variable.
fn condvar_signal(&mut self, id: CondvarId) -> Option<(ThreadId, MutexId)> {
let this = self.eval_context_mut();
- this.machine.threads.sync.condvars[id]
- .waiters
- .pop_front()
- .map(|waiter| (waiter.thread, waiter.mutex))
+ let current_thread = this.get_active_thread();
+ let condvar = &mut this.machine.threads.sync.condvars[id];
+ let data_race = &this.memory.extra.data_race;
+
+ // Each condvar signal happens-before the end of the condvar wake
+ if let Some(data_race) = data_race {
+ data_race.validate_lock_release(&mut condvar.data_race, current_thread);
+ }
+ condvar.waiters.pop_front().map(|waiter| {
+ if let Some(data_race) = data_race {
+ data_race.validate_lock_acquire(&mut condvar.data_race, waiter.thread);
+ }
+ (waiter.thread, waiter.mutex)
+ })
}
#[inline]
let this = self.eval_context_mut();
this.machine.threads.sync.condvars[id].waiters.retain(|waiter| waiter.thread != thread);
}
+
+ fn futex_wait(&mut self, addr: u64, thread: ThreadId) {
+ let this = self.eval_context_mut();
+ let futex = &mut this.machine.threads.sync.futexes.entry(addr).or_default();
+ let waiters = &mut futex.waiters;
+ assert!(waiters.iter().all(|waiter| waiter.thread != thread), "thread is already waiting");
+ waiters.push_back(FutexWaiter { thread });
+ }
+
+ fn futex_wake(&mut self, addr: u64) -> Option<ThreadId> {
+ let this = self.eval_context_mut();
+ let current_thread = this.get_active_thread();
+ let futex = &mut this.machine.threads.sync.futexes.get_mut(&addr)?;
+ let data_race = &this.memory.extra.data_race;
+
+ // Each futex-wake happens-before the end of the futex wait
+ if let Some(data_race) = data_race {
+ data_race.validate_lock_release(&mut futex.data_race, current_thread);
+ }
+ let res = futex.waiters.pop_front().map(|waiter| {
+ if let Some(data_race) = data_race {
+ data_race.validate_lock_acquire(&futex.data_race, waiter.thread);
+ }
+ waiter.thread
+ });
+ res
+ }
+
+ fn futex_remove_waiter(&mut self, addr: u64, thread: ThreadId) {
+ let this = self.eval_context_mut();
+ if let Some(futex) = this.machine.threads.sync.futexes.get_mut(&addr) {
+ futex.waiters.retain(|waiter| waiter.thread != thread);
+ }
+ }
}
projects / rust.git / blobdiff