1 pub use ::alloc::sync::Arc;
2 use core::ops::{Deref, DerefMut};
3 use core::time::Duration;
5 use std::cell::RefCell;
7 use std::sync::atomic::{AtomicUsize, Ordering};
8 use std::sync::Mutex as StdMutex;
9 use std::sync::MutexGuard as StdMutexGuard;
10 use std::sync::RwLock as StdRwLock;
11 use std::sync::RwLockReadGuard as StdRwLockReadGuard;
12 use std::sync::RwLockWriteGuard as StdRwLockWriteGuard;
13 use std::sync::Condvar as StdCondvar;
15 use crate::prelude::HashMap;
17 use super::{LockTestExt, LockHeldState};
19 #[cfg(feature = "backtrace")]
20 use {crate::prelude::hash_map, backtrace::Backtrace, std::sync::Once};
22 #[cfg(not(feature = "backtrace"))]
24 #[cfg(not(feature = "backtrace"))]
25 impl Backtrace { fn new() -> Backtrace { Backtrace {} } }
27 pub type LockResult<Guard> = Result<Guard, ()>;
34 pub fn new() -> Condvar {
35 Condvar { inner: StdCondvar::new() }
38 pub fn wait<'a, T>(&'a self, guard: MutexGuard<'a, T>) -> LockResult<MutexGuard<'a, T>> {
39 let mutex: &'a Mutex<T> = guard.mutex;
40 self.inner.wait(guard.into_inner()).map(|lock| MutexGuard { mutex, lock }).map_err(|_| ())
44 pub fn wait_timeout<'a, T>(&'a self, guard: MutexGuard<'a, T>, dur: Duration) -> LockResult<(MutexGuard<'a, T>, ())> {
45 let mutex = guard.mutex;
46 self.inner.wait_timeout(guard.into_inner(), dur).map(|(lock, _)| (MutexGuard { mutex, lock }, ())).map_err(|_| ())
49 pub fn notify_all(&self) { self.inner.notify_all(); }
53 /// We track the set of locks currently held by a reference to their `LockMetadata`
54 static LOCKS_HELD: RefCell<HashMap<u64, Arc<LockMetadata>>> = RefCell::new(HashMap::new());
56 static LOCK_IDX: AtomicUsize = AtomicUsize::new(0);
58 #[cfg(feature = "backtrace")]
59 static mut LOCKS: Option<StdMutex<HashMap<String, Arc<LockMetadata>>>> = None;
60 #[cfg(feature = "backtrace")]
61 static LOCKS_INIT: Once = Once::new();
63 /// Metadata about a single lock, by id, the set of things locked-before it, and the backtrace of
64 /// when the Mutex itself was constructed.
67 locked_before: StdMutex<HashMap<u64, LockDep>>,
68 _lock_construction_bt: Backtrace,
72 lock: Arc<LockMetadata>,
73 /// lockdep_trace is unused unless we're building with `backtrace`, so we mark it _
74 _lockdep_trace: Backtrace,
77 #[cfg(feature = "backtrace")]
78 fn get_construction_location(backtrace: &Backtrace) -> String {
79 // Find the first frame that is after `debug_sync` (or that is in our tests) and use
80 // that as the mutex construction site. Note that the first few frames may be in
81 // the `backtrace` crate, so we have to ignore those.
82 let sync_mutex_constr_regex = regex::Regex::new(r"lightning.*debug_sync").unwrap();
83 let mut found_debug_sync = false;
84 for frame in backtrace.frames() {
85 for symbol in frame.symbols() {
86 let symbol_name = symbol.name().unwrap().as_str().unwrap();
87 if !sync_mutex_constr_regex.is_match(symbol_name) {
89 if let Some(col) = symbol.colno() {
90 return format!("{}:{}:{}", symbol.filename().unwrap().display(), symbol.lineno().unwrap(), col);
92 // Windows debug symbols don't support column numbers, so fall back to
93 // line numbers only if no `colno` is available
94 return format!("{}:{}", symbol.filename().unwrap().display(), symbol.lineno().unwrap());
97 } else { found_debug_sync = true; }
100 panic!("Couldn't find mutex construction callsite");
104 fn new() -> Arc<LockMetadata> {
105 let backtrace = Backtrace::new();
106 let lock_idx = LOCK_IDX.fetch_add(1, Ordering::Relaxed) as u64;
108 let res = Arc::new(LockMetadata {
109 locked_before: StdMutex::new(HashMap::new()),
111 _lock_construction_bt: backtrace,
114 #[cfg(feature = "backtrace")]
116 let lock_constr_location = get_construction_location(&res._lock_construction_bt);
117 LOCKS_INIT.call_once(|| { unsafe { LOCKS = Some(StdMutex::new(HashMap::new())); } });
118 let mut locks = unsafe { LOCKS.as_ref() }.unwrap().lock().unwrap();
119 match locks.entry(lock_constr_location) {
120 hash_map::Entry::Occupied(e) => return Arc::clone(e.get()),
121 hash_map::Entry::Vacant(e) => { e.insert(Arc::clone(&res)); },
127 // Returns whether we were a recursive lock (only relevant for read)
128 fn _pre_lock(this: &Arc<LockMetadata>, read: bool) -> bool {
129 let mut inserted = false;
130 LOCKS_HELD.with(|held| {
131 // For each lock which is currently locked, check that no lock's locked-before
132 // set includes the lock we're about to lock, which would imply a lockorder
134 for (locked_idx, _locked) in held.borrow().iter() {
135 if read && *locked_idx == this.lock_idx {
136 // Recursive read locks are explicitly allowed
140 for (locked_idx, locked) in held.borrow().iter() {
141 if !read && *locked_idx == this.lock_idx {
142 // With `feature = "backtrace"` set, we may be looking at different instances
144 debug_assert!(cfg!(feature = "backtrace"), "Tried to acquire a lock while it was held!");
146 for (locked_dep_idx, _locked_dep) in locked.locked_before.lock().unwrap().iter() {
147 if *locked_dep_idx == this.lock_idx && *locked_dep_idx != locked.lock_idx {
148 #[cfg(feature = "backtrace")]
149 panic!("Tried to violate existing lockorder.\nMutex that should be locked after the current lock was created at the following backtrace.\nNote that to get a backtrace for the lockorder violation, you should set RUST_BACKTRACE=1\nLock being taken constructed at: {} ({}):\n{:?}\nLock constructed at: {} ({})\n{:?}\n\nLock dep created at:\n{:?}\n\n",
150 get_construction_location(&this._lock_construction_bt), this.lock_idx, this._lock_construction_bt,
151 get_construction_location(&locked._lock_construction_bt), locked.lock_idx, locked._lock_construction_bt,
152 _locked_dep._lockdep_trace);
153 #[cfg(not(feature = "backtrace"))]
154 panic!("Tried to violate existing lockorder. Build with the backtrace feature for more info.");
157 // Insert any already-held locks in our locked-before set.
158 let mut locked_before = this.locked_before.lock().unwrap();
159 if !locked_before.contains_key(&locked.lock_idx) {
160 let lockdep = LockDep { lock: Arc::clone(locked), _lockdep_trace: Backtrace::new() };
161 locked_before.insert(lockdep.lock.lock_idx, lockdep);
164 held.borrow_mut().insert(this.lock_idx, Arc::clone(this));
170 fn pre_lock(this: &Arc<LockMetadata>) { Self::_pre_lock(this, false); }
171 fn pre_read_lock(this: &Arc<LockMetadata>) -> bool { Self::_pre_lock(this, true) }
173 fn held_by_thread(this: &Arc<LockMetadata>) -> LockHeldState {
174 let mut res = LockHeldState::NotHeldByThread;
175 LOCKS_HELD.with(|held| {
176 for (locked_idx, _locked) in held.borrow().iter() {
177 if *locked_idx == this.lock_idx {
178 res = LockHeldState::HeldByThread;
185 fn try_locked(this: &Arc<LockMetadata>) {
186 LOCKS_HELD.with(|held| {
187 // Since a try-lock will simply fail if the lock is held already, we do not
188 // consider try-locks to ever generate lockorder inversions. However, if a try-lock
189 // succeeds, we do consider it to have created lockorder dependencies.
190 let mut locked_before = this.locked_before.lock().unwrap();
191 for (locked_idx, locked) in held.borrow().iter() {
192 if !locked_before.contains_key(locked_idx) {
193 let lockdep = LockDep { lock: Arc::clone(locked), _lockdep_trace: Backtrace::new() };
194 locked_before.insert(*locked_idx, lockdep);
197 held.borrow_mut().insert(this.lock_idx, Arc::clone(this));
202 pub struct Mutex<T: Sized> {
204 deps: Arc<LockMetadata>,
207 #[must_use = "if unused the Mutex will immediately unlock"]
208 pub struct MutexGuard<'a, T: Sized + 'a> {
210 lock: StdMutexGuard<'a, T>,
213 impl<'a, T: Sized> MutexGuard<'a, T> {
214 fn into_inner(self) -> StdMutexGuard<'a, T> {
215 // Somewhat unclear why we cannot move out of self.lock, but doing so gets E0509.
217 let v: StdMutexGuard<'a, T> = std::ptr::read(&self.lock);
218 std::mem::forget(self);
224 impl<T: Sized> Drop for MutexGuard<'_, T> {
226 LOCKS_HELD.with(|held| {
227 held.borrow_mut().remove(&self.mutex.deps.lock_idx);
232 impl<T: Sized> Deref for MutexGuard<'_, T> {
235 fn deref(&self) -> &T {
240 impl<T: Sized> DerefMut for MutexGuard<'_, T> {
241 fn deref_mut(&mut self) -> &mut T {
242 self.lock.deref_mut()
247 pub fn new(inner: T) -> Mutex<T> {
248 Mutex { inner: StdMutex::new(inner), deps: LockMetadata::new() }
251 pub fn lock<'a>(&'a self) -> LockResult<MutexGuard<'a, T>> {
252 LockMetadata::pre_lock(&self.deps);
253 self.inner.lock().map(|lock| MutexGuard { mutex: self, lock }).map_err(|_| ())
256 pub fn try_lock<'a>(&'a self) -> LockResult<MutexGuard<'a, T>> {
257 let res = self.inner.try_lock().map(|lock| MutexGuard { mutex: self, lock }).map_err(|_| ());
259 LockMetadata::try_locked(&self.deps);
265 impl <T> LockTestExt for Mutex<T> {
267 fn held_by_thread(&self) -> LockHeldState {
268 LockMetadata::held_by_thread(&self.deps)
272 pub struct RwLock<T: Sized> {
274 deps: Arc<LockMetadata>,
277 pub struct RwLockReadGuard<'a, T: Sized + 'a> {
280 guard: StdRwLockReadGuard<'a, T>,
283 pub struct RwLockWriteGuard<'a, T: Sized + 'a> {
285 guard: StdRwLockWriteGuard<'a, T>,
288 impl<T: Sized> Deref for RwLockReadGuard<'_, T> {
291 fn deref(&self) -> &T {
296 impl<T: Sized> Drop for RwLockReadGuard<'_, T> {
298 if !self.first_lock {
299 // Note that its not strictly true that the first taken read lock will get unlocked
300 // last, but in practice our locks are always taken as RAII, so it should basically
304 LOCKS_HELD.with(|held| {
305 held.borrow_mut().remove(&self.lock.deps.lock_idx);
310 impl<T: Sized> Deref for RwLockWriteGuard<'_, T> {
313 fn deref(&self) -> &T {
318 impl<T: Sized> Drop for RwLockWriteGuard<'_, T> {
320 LOCKS_HELD.with(|held| {
321 held.borrow_mut().remove(&self.lock.deps.lock_idx);
326 impl<T: Sized> DerefMut for RwLockWriteGuard<'_, T> {
327 fn deref_mut(&mut self) -> &mut T {
328 self.guard.deref_mut()
333 pub fn new(inner: T) -> RwLock<T> {
334 RwLock { inner: StdRwLock::new(inner), deps: LockMetadata::new() }
337 pub fn read<'a>(&'a self) -> LockResult<RwLockReadGuard<'a, T>> {
338 let first_lock = LockMetadata::pre_read_lock(&self.deps);
339 self.inner.read().map(|guard| RwLockReadGuard { lock: self, guard, first_lock }).map_err(|_| ())
342 pub fn write<'a>(&'a self) -> LockResult<RwLockWriteGuard<'a, T>> {
343 LockMetadata::pre_lock(&self.deps);
344 self.inner.write().map(|guard| RwLockWriteGuard { lock: self, guard }).map_err(|_| ())
347 pub fn try_write<'a>(&'a self) -> LockResult<RwLockWriteGuard<'a, T>> {
348 let res = self.inner.try_write().map(|guard| RwLockWriteGuard { lock: self, guard }).map_err(|_| ());
350 LockMetadata::try_locked(&self.deps);
356 impl <T> LockTestExt for RwLock<T> {
358 fn held_by_thread(&self) -> LockHeldState {
359 LockMetadata::held_by_thread(&self.deps)
363 pub type FairRwLock<T> = RwLock<T>;