2020-04-21 18:38:14 -05:00
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use std::collections::{hash_map::Entry, HashMap, VecDeque};
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use std::convert::TryFrom;
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use std::num::NonZeroU32;
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use rustc_index::vec::{Idx, IndexVec};
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use crate::*;
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macro_rules! declare_id {
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($name: ident) => {
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2020-04-30 16:07:07 -05:00
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/// 0 is used to indicate that the id was not yet assigned and,
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/// therefore, is not a valid identifier.
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2020-04-21 18:38:14 -05:00
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#[derive(Clone, Copy, Debug, PartialOrd, Ord, PartialEq, Eq, Hash)]
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pub struct $name(NonZeroU32);
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2020-04-30 16:07:07 -05:00
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impl $name {
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// Panics if `id == 0`.
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pub fn from_u32(id: u32) -> Self {
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Self(NonZeroU32::new(id).unwrap())
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}
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}
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2020-04-21 18:38:14 -05:00
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impl Idx for $name {
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fn new(idx: usize) -> Self {
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$name(NonZeroU32::new(u32::try_from(idx).unwrap() + 1).unwrap())
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}
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fn index(self) -> usize {
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usize::try_from(self.0.get() - 1).unwrap()
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}
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}
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impl $name {
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pub fn to_u32_scalar<'tcx>(&self) -> Scalar<Tag> {
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Scalar::from_u32(self.0.get())
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}
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}
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};
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}
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declare_id!(MutexId);
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/// The mutex state.
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#[derive(Default, Debug)]
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struct Mutex {
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/// The thread that currently owns the lock.
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owner: Option<ThreadId>,
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/// How many times the mutex was locked by the owner.
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lock_count: usize,
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/// The queue of threads waiting for this mutex.
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queue: VecDeque<ThreadId>,
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}
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declare_id!(RwLockId);
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/// The read-write lock state.
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#[derive(Default, Debug)]
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struct RwLock {
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/// The writer thread that currently owns the lock.
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writer: Option<ThreadId>,
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/// The readers that currently own the lock and how many times they acquired
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/// the lock.
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readers: HashMap<ThreadId, usize>,
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/// The queue of writer threads waiting for this lock.
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writer_queue: VecDeque<ThreadId>,
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/// The queue of reader threads waiting for this lock.
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reader_queue: VecDeque<ThreadId>,
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}
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declare_id!(CondvarId);
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/// A thread waiting on a conditional variable.
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#[derive(Debug)]
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struct CondvarWaiter {
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/// The thread that is waiting on this variable.
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thread: ThreadId,
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/// The mutex on which the thread is waiting.
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mutex: MutexId,
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}
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/// The conditional variable state.
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#[derive(Default, Debug)]
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struct Condvar {
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waiters: VecDeque<CondvarWaiter>,
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}
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/// The state of all synchronization variables.
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#[derive(Default, Debug)]
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pub(super) struct SynchronizationState {
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mutexes: IndexVec<MutexId, Mutex>,
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rwlocks: IndexVec<RwLockId, RwLock>,
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condvars: IndexVec<CondvarId, Condvar>,
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}
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// Public interface to synchronization primitives. Please note that in most
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// cases, the function calls are infallible and it is the client's (shim
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// implementation's) responsibility to detect and deal with erroneous
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// situations.
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impl<'mir, 'tcx: 'mir> EvalContextExt<'mir, 'tcx> for crate::MiriEvalContext<'mir, 'tcx> {}
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pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx> {
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#[inline]
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/// Create state for a new mutex.
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fn mutex_create(&mut self) -> MutexId {
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let this = self.eval_context_mut();
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this.machine.threads.sync.mutexes.push(Default::default())
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}
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#[inline]
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/// Get the id of the thread that currently owns this lock.
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fn mutex_get_owner(&mut self, id: MutexId) -> ThreadId {
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let this = self.eval_context_ref();
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this.machine.threads.sync.mutexes[id].owner.unwrap()
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}
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#[inline]
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/// Check if locked.
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fn mutex_is_locked(&mut self, id: MutexId) -> bool {
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let this = self.eval_context_mut();
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this.machine.threads.sync.mutexes[id].owner.is_some()
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}
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/// Lock by setting the mutex owner and increasing the lock count.
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fn mutex_lock(&mut self, id: MutexId, thread: ThreadId) {
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let this = self.eval_context_mut();
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let mutex = &mut this.machine.threads.sync.mutexes[id];
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if let Some(current_owner) = mutex.owner {
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assert_eq!(thread, current_owner, "mutex already locked by another thread");
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assert!(
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mutex.lock_count > 0,
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"invariant violation: lock_count == 0 iff the thread is unlocked"
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);
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} else {
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mutex.owner = Some(thread);
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}
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mutex.lock_count = mutex.lock_count.checked_add(1).unwrap();
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}
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/// Unlock by decreasing the lock count. If the lock count reaches 0, unset
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/// the owner.
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fn mutex_unlock(&mut self, id: MutexId) -> Option<(ThreadId, usize)> {
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let this = self.eval_context_mut();
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let mutex = &mut this.machine.threads.sync.mutexes[id];
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if let Some(current_owner) = mutex.owner {
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mutex.lock_count = mutex
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.lock_count
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.checked_sub(1)
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.expect("invariant violation: lock_count == 0 iff the thread is unlocked");
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if mutex.lock_count == 0 {
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mutex.owner = None;
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}
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Some((current_owner, mutex.lock_count))
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} else {
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None
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}
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}
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#[inline]
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/// Take a thread out the queue waiting for the lock.
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fn mutex_enqueue(&mut self, id: MutexId, thread: ThreadId) {
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let this = self.eval_context_mut();
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this.machine.threads.sync.mutexes[id].queue.push_back(thread);
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}
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#[inline]
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/// Take a thread out the queue waiting for the lock.
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fn mutex_dequeue(&mut self, id: MutexId) -> Option<ThreadId> {
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let this = self.eval_context_mut();
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this.machine.threads.sync.mutexes[id].queue.pop_front()
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}
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#[inline]
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/// Create state for a new read write lock.
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fn rwlock_create(&mut self) -> RwLockId {
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let this = self.eval_context_mut();
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this.machine.threads.sync.rwlocks.push(Default::default())
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}
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#[inline]
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/// Check if locked.
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fn rwlock_is_locked(&mut self, id: RwLockId) -> bool {
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let this = self.eval_context_mut();
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this.machine.threads.sync.rwlocks[id].writer.is_some()
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|| !this.machine.threads.sync.rwlocks[id].readers.is_empty()
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}
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#[inline]
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/// Check if write locked.
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fn rwlock_is_write_locked(&mut self, id: RwLockId) -> bool {
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let this = self.eval_context_mut();
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this.machine.threads.sync.rwlocks[id].writer.is_some()
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}
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/// Add a reader that collectively with other readers owns the lock.
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fn rwlock_reader_add(&mut self, id: RwLockId, reader: ThreadId) {
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let this = self.eval_context_mut();
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assert!(!this.rwlock_is_write_locked(id), "the lock is write locked");
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let count = this.machine.threads.sync.rwlocks[id].readers.entry(reader).or_insert(0);
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*count += 1;
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}
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/// Try removing the reader. Returns `true` if succeeded.
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fn rwlock_reader_remove(&mut self, id: RwLockId, reader: ThreadId) -> bool {
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let this = self.eval_context_mut();
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match this.machine.threads.sync.rwlocks[id].readers.entry(reader) {
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Entry::Occupied(mut entry) => {
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let count = entry.get_mut();
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*count -= 1;
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if *count == 0 {
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entry.remove();
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}
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true
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}
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Entry::Vacant(_) => false,
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}
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}
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#[inline]
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/// Put the reader in the queue waiting for the lock.
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fn rwlock_enqueue_reader(&mut self, id: RwLockId, reader: ThreadId) {
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let this = self.eval_context_mut();
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assert!(this.rwlock_is_write_locked(id), "queueing on not write locked lock");
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this.machine.threads.sync.rwlocks[id].reader_queue.push_back(reader);
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}
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#[inline]
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/// Take the reader out the queue waiting for the lock.
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fn rwlock_dequeue_reader(&mut self, id: RwLockId) -> Option<ThreadId> {
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let this = self.eval_context_mut();
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this.machine.threads.sync.rwlocks[id].reader_queue.pop_front()
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}
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#[inline]
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/// Lock by setting the writer that owns the lock.
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fn rwlock_writer_set(&mut self, id: RwLockId, writer: ThreadId) {
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let this = self.eval_context_mut();
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assert!(!this.rwlock_is_locked(id), "the lock is already locked");
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this.machine.threads.sync.rwlocks[id].writer = Some(writer);
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}
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#[inline]
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/// Try removing the writer.
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fn rwlock_writer_remove(&mut self, id: RwLockId) -> Option<ThreadId> {
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let this = self.eval_context_mut();
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this.machine.threads.sync.rwlocks[id].writer.take()
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}
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#[inline]
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/// Put the writer in the queue waiting for the lock.
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fn rwlock_enqueue_writer(&mut self, id: RwLockId, writer: ThreadId) {
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let this = self.eval_context_mut();
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assert!(this.rwlock_is_locked(id), "queueing on unlocked lock");
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this.machine.threads.sync.rwlocks[id].writer_queue.push_back(writer);
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}
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#[inline]
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/// Take the writer out the queue waiting for the lock.
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fn rwlock_dequeue_writer(&mut self, id: RwLockId) -> Option<ThreadId> {
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let this = self.eval_context_mut();
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this.machine.threads.sync.rwlocks[id].writer_queue.pop_front()
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}
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#[inline]
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/// Create state for a new conditional variable.
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fn condvar_create(&mut self) -> CondvarId {
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let this = self.eval_context_mut();
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this.machine.threads.sync.condvars.push(Default::default())
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}
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#[inline]
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/// Is the conditional variable awaited?
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fn condvar_is_awaited(&mut self, id: CondvarId) -> bool {
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let this = self.eval_context_mut();
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!this.machine.threads.sync.condvars[id].waiters.is_empty()
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}
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/// Mark that the thread is waiting on the conditional variable.
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fn condvar_wait(&mut self, id: CondvarId, thread: ThreadId, mutex: MutexId) {
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let this = self.eval_context_mut();
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let waiters = &mut this.machine.threads.sync.condvars[id].waiters;
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assert!(waiters.iter().all(|waiter| waiter.thread != thread), "thread is already waiting");
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2020-05-18 09:28:19 -05:00
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waiters.push_back(CondvarWaiter { thread, mutex });
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2020-04-21 18:38:14 -05:00
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}
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/// Wake up some thread (if there is any) sleeping on the conditional
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/// variable.
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fn condvar_signal(&mut self, id: CondvarId) -> Option<(ThreadId, MutexId)> {
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let this = self.eval_context_mut();
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this.machine.threads.sync.condvars[id]
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.waiters
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.pop_front()
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.map(|waiter| (waiter.thread, waiter.mutex))
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}
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#[inline]
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/// Remove the thread from the queue of threads waiting on this conditional variable.
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fn condvar_remove_waiter(&mut self, id: CondvarId, thread: ThreadId) {
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let this = self.eval_context_mut();
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this.machine.threads.sync.condvars[id].waiters.retain(|waiter| waiter.thread != thread);
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}
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}
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