use std::cell::RefCell;
use std::collections::HashSet;
use std::marker::PhantomData;
use crate::collection::utils;
use crate::handle_unwind::handle_unwind;
use crate::lockable::{
Lockable, LockableGetMut, LockableIntoInner, OwnedLockable, RawLock, Sharable,
};
use crate::Keyable;
use super::{LockGuard, RetryingLockCollection};
/// Get all raw locks in the collection
fn get_locks<L: Lockable>(data: &L) -> Vec<&dyn RawLock> {
let mut locks = Vec::new();
data.get_ptrs(&mut locks);
locks
}
/// Checks that a collection contains no duplicate references to a lock.
fn contains_duplicates<L: Lockable>(data: L) -> bool {
let mut locks = Vec::new();
data.get_ptrs(&mut locks);
// cast to *const () so that the v-table pointers are not used for hashing
let locks = locks.into_iter().map(|l| (&raw const *l).cast::<()>());
let mut locks_set = HashSet::with_capacity(locks.len());
for lock in locks {
if !locks_set.insert(lock) {
return true;
}
}
false
}
unsafe impl<L: Lockable> RawLock for RetryingLockCollection<L> {
fn poison(&self) {
let locks = get_locks(&self.data);
for lock in locks {
lock.poison();
}
}
unsafe fn raw_lock(&self) {
let mut first_index = 0;
let locks = get_locks(&self.data);
if locks.is_empty() {
// this probably prevents a panic later
return;
}
// these will be unlocked in case of a panic
let locked = RefCell::new(Vec::with_capacity(locks.len()));
handle_unwind(
|| unsafe {
'outer: loop {
// This prevents us from entering a spin loop waiting for
// the same lock to be unlocked
// safety: we have the thread key
locks[first_index].raw_lock();
for (i, lock) in locks.iter().enumerate() {
if i == first_index {
// we've already locked this one
continue;
}
// If the lock has been killed, then this returns false
// instead of panicking. This sounds like a problem, but if
// it does return false, then the lock function is called
// immediately after, causing a panic
// safety: we have the thread key
if lock.raw_try_lock() {
locked.borrow_mut().push(*lock)
} else {
for lock in locked.borrow().iter() {
// safety: we already locked all of these
lock.raw_unlock();
}
// these are no longer locked
locked.borrow_mut().clear();
if first_index >= i {
// safety: this is already locked and can't be unlocked
// by the previous loop
locks[first_index].raw_unlock();
}
// call lock on this to prevent a spin loop
first_index = i;
continue 'outer;
}
}
// safety: we locked all the data
break;
}
},
|| utils::attempt_to_recover_locks_from_panic(&locked),
)
}
unsafe fn raw_try_lock(&self) -> bool {
let locks = get_locks(&self.data);
if locks.is_empty() {
// this is an interesting case, but it doesn't give us access to
// any data, and can't possibly cause a deadlock
return true;
}
// these will be unlocked in case of a panic
let locked = RefCell::new(Vec::with_capacity(locks.len()));
handle_unwind(
|| unsafe {
for (i, lock) in locks.iter().enumerate() {
// safety: we have the thread key
if lock.raw_try_lock() {
locked.borrow_mut().push(*lock);
} else {
for lock in locks.iter().take(i) {
// safety: we already locked all of these
lock.raw_unlock();
}
return false;
}
}
true
},
|| utils::attempt_to_recover_locks_from_panic(&locked),
)
}
unsafe fn raw_unlock(&self) {
let locks = get_locks(&self.data);
for lock in locks {
lock.raw_unlock();
}
}
unsafe fn raw_read(&self) {
let mut first_index = 0;
let locks = get_locks(&self.data);
if locks.is_empty() {
// this probably prevents a panic later
return;
}
let locked = RefCell::new(Vec::with_capacity(locks.len()));
handle_unwind(
|| 'outer: loop {
// safety: we have the thread key
locks[first_index].raw_read();
for (i, lock) in locks.iter().enumerate() {
if i == first_index {
continue;
}
// safety: we have the thread key
if lock.raw_try_read() {
locked.borrow_mut().push(*lock);
} else {
for lock in locked.borrow().iter() {
// safety: we already locked all of these
lock.raw_unlock_read();
}
// these are no longer locked
locked.borrow_mut().clear();
if first_index >= i {
// safety: this is already locked and can't be unlocked
// by the previous loop
locks[first_index].raw_unlock_read();
}
// don't go into a spin loop, wait for this one to lock
first_index = i;
continue 'outer;
}
}
// safety: we locked all the data
break;
},
|| utils::attempt_to_recover_reads_from_panic(&locked),
)
}
unsafe fn raw_try_read(&self) -> bool {
let locks = get_locks(&self.data);
if locks.is_empty() {
// this is an interesting case, but it doesn't give us access to
// any data, and can't possibly cause a deadlock
return true;
}
let locked = RefCell::new(Vec::with_capacity(locks.len()));
handle_unwind(
|| unsafe {
for (i, lock) in locks.iter().enumerate() {
// safety: we have the thread key
if lock.raw_try_read() {
locked.borrow_mut().push(*lock);
} else {
for lock in locks.iter().take(i) {
// safety: we already locked all of these
lock.raw_unlock_read();
}
return false;
}
}
true
},
|| utils::attempt_to_recover_reads_from_panic(&locked),
)
}
unsafe fn raw_unlock_read(&self) {
let locks = get_locks(&self.data);
for lock in locks {
lock.raw_unlock_read();
}
}
}
unsafe impl<L: Lockable> Lockable for RetryingLockCollection<L> {
type Guard<'g>
= L::Guard<'g>
where
Self: 'g;
fn get_ptrs<'a>(&'a self, ptrs: &mut Vec<&'a dyn RawLock>) {
self.data.get_ptrs(ptrs)
}
unsafe fn guard(&self) -> Self::Guard<'_> {
self.data.guard()
}
}
unsafe impl<L: Sharable> Sharable for RetryingLockCollection<L> {
type ReadGuard<'g>
= L::ReadGuard<'g>
where
Self: 'g;
unsafe fn read_guard(&self) -> Self::ReadGuard<'_> {
self.data.read_guard()
}
}
unsafe impl<L: OwnedLockable> OwnedLockable for RetryingLockCollection<L> {}
impl<L: LockableGetMut> LockableGetMut for RetryingLockCollection<L> {
type Inner<'a>
= L::Inner<'a>
where
Self: 'a;
fn get_mut(&mut self) -> Self::Inner<'_> {
self.data.get_mut()
}
}
impl<L: LockableIntoInner> LockableIntoInner for RetryingLockCollection<L> {
type Inner = L::Inner;
fn into_inner(self) -> Self::Inner {
self.data.into_inner()
}
}
impl<L> IntoIterator for RetryingLockCollection<L>
where
L: IntoIterator,
{
type Item = <L as IntoIterator>::Item;
type IntoIter = <L as IntoIterator>::IntoIter;
fn into_iter(self) -> Self::IntoIter {
self.data.into_iter()
}
}
impl<'a, L> IntoIterator for &'a RetryingLockCollection<L>
where
&'a L: IntoIterator,
{
type Item = <&'a L as IntoIterator>::Item;
type IntoIter = <&'a L as IntoIterator>::IntoIter;
fn into_iter(self) -> Self::IntoIter {
self.data.into_iter()
}
}
impl<'a, L> IntoIterator for &'a mut RetryingLockCollection<L>
where
&'a mut L: IntoIterator,
{
type Item = <&'a mut L as IntoIterator>::Item;
type IntoIter = <&'a mut L as IntoIterator>::IntoIter;
fn into_iter(self) -> Self::IntoIter {
self.data.into_iter()
}
}
impl<L: OwnedLockable, I: FromIterator<L> + OwnedLockable> FromIterator<L>
for RetryingLockCollection<I>
{
fn from_iter<T: IntoIterator<Item = L>>(iter: T) -> Self {
let iter: I = iter.into_iter().collect();
Self::new(iter)
}
}
impl<E: OwnedLockable + Extend<L>, L: OwnedLockable> Extend<L> for RetryingLockCollection<E> {
fn extend<T: IntoIterator<Item = L>>(&mut self, iter: T) {
self.data.extend(iter)
}
}
impl<T, L: AsRef<T>> AsRef<T> for RetryingLockCollection<L> {
fn as_ref(&self) -> &T {
self.data.as_ref()
}
}
impl<T, L: AsMut<T>> AsMut<T> for RetryingLockCollection<L> {
fn as_mut(&mut self) -> &mut T {
self.data.as_mut()
}
}
impl<L: OwnedLockable + Default> Default for RetryingLockCollection<L> {
fn default() -> Self {
Self::new(L::default())
}
}
impl<L: OwnedLockable> From<L> for RetryingLockCollection<L> {
fn from(value: L) -> Self {
Self::new(value)
}
}
impl<L: OwnedLockable> RetryingLockCollection<L> {
/// Creates a new collection of owned locks.
///
/// Because the locks are owned, there's no need to do any checks for
/// duplicate values. The locks also don't need to be sorted by memory
/// address because they aren't used anywhere else.
///
/// # Examples
///
/// ```
/// use happylock::Mutex;
/// use happylock::collection::RetryingLockCollection;
///
/// let data = (Mutex::new(0), Mutex::new(""));
/// let lock = RetryingLockCollection::new(data);
/// ```
#[must_use]
pub const fn new(data: L) -> Self {
Self { data }
}
}
impl<'a, L: OwnedLockable> RetryingLockCollection<&'a L> {
/// Creates a new collection of owned locks.
///
/// Because the locks are owned, there's no need to do any checks for
/// duplicate values.
///
/// # Examples
///
/// ```
/// use happylock::Mutex;
/// use happylock::collection::RetryingLockCollection;
///
/// let data = (Mutex::new(0), Mutex::new(""));
/// let lock = RetryingLockCollection::new_ref(&data);
/// ```
#[must_use]
pub const fn new_ref(data: &'a L) -> Self {
Self { data }
}
}
impl<L> RetryingLockCollection<L> {
/// Creates a new collections of locks.
///
/// # Safety
///
/// This results in undefined behavior if any locks are presented twice
/// within this collection.
///
/// # Examples
///
/// ```
/// use happylock::Mutex;
/// use happylock::collection::RetryingLockCollection;
///
/// let data1 = Mutex::new(0);
/// let data2 = Mutex::new("");
///
/// // safety: data1 and data2 refer to distinct mutexes
/// let data = (&data1, &data2);
/// let lock = unsafe { RetryingLockCollection::new_unchecked(&data) };
/// ```
#[must_use]
pub const unsafe fn new_unchecked(data: L) -> Self {
Self { data }
}
pub const fn child(&self) -> &L {
&self.data
}
pub fn child_mut(&mut self) -> &mut L {
&mut self.data
}
/// Gets the underlying collection, consuming this collection.
///
/// # Examples
///
/// ```
/// use happylock::{Mutex, ThreadKey};
/// use happylock::collection::RetryingLockCollection;
///
/// let data = (Mutex::new(42), Mutex::new(""));
/// let lock = RetryingLockCollection::new(data);
///
/// let key = ThreadKey::get().unwrap();
/// let inner = lock.into_child();
/// let guard = inner.0.lock(key);
/// assert_eq!(*guard, 42);
/// ```
#[must_use]
pub fn into_child(self) -> L {
self.data
}
}
impl<L: Lockable> RetryingLockCollection<L> {
/// Creates a new collection of locks.
///
/// This returns `None` if any locks are found twice in the given
/// collection.
///
/// # Examples
///
/// ```
/// use happylock::Mutex;
/// use happylock::collection::RetryingLockCollection;
///
/// let data1 = Mutex::new(0);
/// let data2 = Mutex::new("");
///
/// // data1 and data2 refer to distinct mutexes, so this won't panic
/// let data = (&data1, &data2);
/// let lock = RetryingLockCollection::try_new(&data).unwrap();
/// ```
#[must_use]
pub fn try_new(data: L) -> Option<Self> {
(!contains_duplicates(&data)).then_some(Self { data })
}
/// Locks the collection
///
/// This function returns a guard that can be used to access the underlying
/// data. When the guard is dropped, the locks in the collection are also
/// dropped.
///
/// # Examples
///
/// ```
/// use happylock::{Mutex, ThreadKey};
/// use happylock::collection::RetryingLockCollection;
///
/// let key = ThreadKey::get().unwrap();
/// let data = (Mutex::new(0), Mutex::new(""));
/// let lock = RetryingLockCollection::new(data);
///
/// let mut guard = lock.lock(key);
/// *guard.0 += 1;
/// *guard.1 = "1";
/// ```
pub fn lock<'g, 'key: 'g, Key: Keyable + 'key>(
&'g self,
key: Key,
) -> LockGuard<'key, L::Guard<'g>, Key> {
unsafe {
// safety: we're taking the thread key
self.raw_lock();
LockGuard {
// safety: we just locked the collection
guard: self.guard(),
key,
_phantom: PhantomData,
}
}
}
/// Attempts to lock the without blocking.
///
/// If successful, this method returns a guard that can be used to access
/// the data, and unlocks the data when it is dropped. Otherwise, `None` is
/// returned.
///
/// # Examples
///
/// ```
/// use happylock::{Mutex, ThreadKey};
/// use happylock::collection::RetryingLockCollection;
///
/// let key = ThreadKey::get().unwrap();
/// let data = (Mutex::new(0), Mutex::new(""));
/// let lock = RetryingLockCollection::new(data);
///
/// match lock.try_lock(key) {
/// Ok(mut guard) => {
/// *guard.0 += 1;
/// *guard.1 = "1";
/// },
/// Err(_) => unreachable!(),
/// };
///
/// ```
pub fn try_lock<'g, 'key: 'g, Key: Keyable + 'key>(
&'g self,
key: Key,
) -> Result<LockGuard<'key, L::Guard<'g>, Key>, Key> {
unsafe {
// safety: we're taking the thread key
if self.raw_try_lock() {
Ok(LockGuard {
// safety: we just succeeded in locking everything
guard: self.guard(),
key,
_phantom: PhantomData,
})
} else {
Err(key)
}
}
}
/// Unlocks the underlying lockable data type, returning the key that's
/// associated with it.
///
/// # Examples
///
/// ```
/// use happylock::{Mutex, ThreadKey};
/// use happylock::collection::RetryingLockCollection;
///
/// let key = ThreadKey::get().unwrap();
/// let data = (Mutex::new(0), Mutex::new(""));
/// let lock = RetryingLockCollection::new(data);
///
/// let mut guard = lock.lock(key);
/// *guard.0 += 1;
/// *guard.1 = "1";
/// let key = RetryingLockCollection::<(Mutex<i32>, Mutex<&str>)>::unlock(guard);
/// ```
pub fn unlock<'key, Key: Keyable + 'key>(guard: LockGuard<'key, L::Guard<'_>, Key>) -> Key {
drop(guard.guard);
guard.key
}
}
impl<L: Sharable> RetryingLockCollection<L> {
/// Locks the collection, so that other threads can still read from it
///
/// This function returns a guard that can be used to access the underlying
/// data immutably. When the guard is dropped, the locks in the collection
/// are also dropped.
///
/// # Examples
///
/// ```
/// use happylock::{RwLock, ThreadKey};
/// use happylock::collection::RetryingLockCollection;
///
/// let key = ThreadKey::get().unwrap();
/// let data = (RwLock::new(0), RwLock::new(""));
/// let lock = RetryingLockCollection::new(data);
///
/// let mut guard = lock.read(key);
/// assert_eq!(*guard.0, 0);
/// assert_eq!(*guard.1, "");
/// ```
pub fn read<'g, 'key: 'g, Key: Keyable + 'key>(
&'g self,
key: Key,
) -> LockGuard<'key, L::ReadGuard<'g>, Key> {
unsafe {
// safety: we're taking the thread key
self.raw_read();
LockGuard {
// safety: we just locked the collection
guard: self.read_guard(),
key,
_phantom: PhantomData,
}
}
}
/// Attempts to lock the without blocking, in such a way that other threads
/// can still read from the collection.
///
/// If successful, this method returns a guard that can be used to access
/// the data immutably, and unlocks the data when it is dropped. Otherwise,
/// `None` is returned.
///
/// # Examples
///
/// ```
/// use happylock::{RwLock, ThreadKey};
/// use happylock::collection::RetryingLockCollection;
///
/// let key = ThreadKey::get().unwrap();
/// let data = (RwLock::new(5), RwLock::new("6"));
/// let lock = RetryingLockCollection::new(data);
///
/// match lock.try_read(key) {
/// Some(mut guard) => {
/// assert_eq!(*guard.0, 5);
/// assert_eq!(*guard.1, "6");
/// },
/// None => unreachable!(),
/// };
///
/// ```
pub fn try_read<'g, 'key: 'g, Key: Keyable + 'key>(
&'g self,
key: Key,
) -> Option<LockGuard<'key, L::ReadGuard<'g>, Key>> {
unsafe {
// safety: we're taking the thread key
self.raw_try_lock().then(|| LockGuard {
// safety: we just succeeded in locking everything
guard: self.read_guard(),
key,
_phantom: PhantomData,
})
}
}
/// Unlocks the underlying lockable data type, returning the key that's
/// associated with it.
///
/// # Examples
///
/// ```
/// use happylock::{RwLock, ThreadKey};
/// use happylock::collection::RetryingLockCollection;
///
/// let key = ThreadKey::get().unwrap();
/// let data = (RwLock::new(0), RwLock::new(""));
/// let lock = RetryingLockCollection::new(data);
///
/// let mut guard = lock.read(key);
/// let key = RetryingLockCollection::<(RwLock<i32>, RwLock<&str>)>::unlock_read(guard);
/// ```
pub fn unlock_read<'key, Key: Keyable + 'key>(
guard: LockGuard<'key, L::ReadGuard<'_>, Key>,
) -> Key {
drop(guard.guard);
guard.key
}
}
impl<L: LockableGetMut> RetryingLockCollection<L> {
pub fn get_mut(&mut self) -> L::Inner<'_> {
LockableGetMut::get_mut(self)
}
}
impl<L: LockableIntoInner> RetryingLockCollection<L> {
pub fn into_inner(self) -> L::Inner {
LockableIntoInner::into_inner(self)
}
}
impl<'a, L: 'a> RetryingLockCollection<L>
where
&'a L: IntoIterator,
{
/// Returns an iterator over references to each value in the collection.
///
/// # Examples
///
/// ```
/// use happylock::{Mutex, ThreadKey};
/// use happylock::collection::RetryingLockCollection;
///
/// let key = ThreadKey::get().unwrap();
/// let data = [Mutex::new(26), Mutex::new(1)];
/// let lock = RetryingLockCollection::new(data);
///
/// let mut iter = lock.iter();
/// let mutex = iter.next().unwrap();
/// let guard = mutex.lock(key);
///
/// assert_eq!(*guard, 26);
/// ```
#[must_use]
pub fn iter(&'a self) -> <&'a L as IntoIterator>::IntoIter {
self.into_iter()
}
}
impl<'a, L: 'a> RetryingLockCollection<L>
where
&'a mut L: IntoIterator,
{
/// Returns an iterator over mutable references to each value in the
/// collection.
///
/// # Examples
///
/// ```
/// use happylock::{Mutex, ThreadKey};
/// use happylock::collection::RetryingLockCollection;
///
/// let key = ThreadKey::get().unwrap();
/// let data = [Mutex::new(26), Mutex::new(1)];
/// let mut lock = RetryingLockCollection::new(data);
///
/// let mut iter = lock.iter_mut();
/// let mutex = iter.next().unwrap();
///
/// assert_eq!(*mutex.as_mut(), 26);
/// ```
#[must_use]
pub fn iter_mut(&'a mut self) -> <&'a mut L as IntoIterator>::IntoIter {
self.into_iter()
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::collection::BoxedLockCollection;
use crate::{Mutex, RwLock, ThreadKey};
#[test]
fn nonduplicate_lock_references_are_allowed() {
let mutex1 = Mutex::new(0);
let mutex2 = Mutex::new(0);
assert!(RetryingLockCollection::try_new([&mutex1, &mutex2]).is_some());
}
#[test]
fn duplicate_lock_references_are_disallowed() {
let mutex = Mutex::new(0);
assert!(RetryingLockCollection::try_new([&mutex, &mutex]).is_none());
}
#[test]
fn locks_all_inner_mutexes() {
let key = ThreadKey::get().unwrap();
let mutex1 = Mutex::new(0);
let mutex2 = Mutex::new(0);
let collection = RetryingLockCollection::try_new([&mutex1, &mutex2]).unwrap();
let guard = collection.lock(key);
assert!(mutex1.is_locked());
assert!(mutex2.is_locked());
drop(guard);
}
#[test]
fn locks_all_inner_rwlocks() {
let key = ThreadKey::get().unwrap();
let rwlock1 = RwLock::new(0);
let rwlock2 = RwLock::new(0);
let collection = RetryingLockCollection::try_new([&rwlock1, &rwlock2]).unwrap();
// TODO Poisonable::read
let guard = collection.read(key);
assert!(rwlock1.is_locked());
assert!(rwlock2.is_locked());
drop(guard);
}
#[test]
fn works_with_other_collections() {
let key = ThreadKey::get().unwrap();
let mutex1 = Mutex::new(0);
let mutex2 = Mutex::new(0);
let collection = BoxedLockCollection::try_new(
RetryingLockCollection::try_new([&mutex1, &mutex2]).unwrap(),
)
.unwrap();
let guard = collection.lock(key);
assert!(mutex1.is_locked());
assert!(mutex2.is_locked());
drop(guard);
}
#[test]
fn extend_collection() {
let mutex1 = Mutex::new(0);
let mutex2 = Mutex::new(0);
let mut collection = RetryingLockCollection::new(vec![mutex1]);
collection.extend([mutex2]);
assert_eq!(collection.into_inner().len(), 2);
}
}
|
