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 fn pre_lock(this: &Arc<LockMetadata>) {
128 LOCKS_HELD.with(|held| {
129 // For each lock which is currently locked, check that no lock's locked-before
130 // set includes the lock we're about to lock, which would imply a lockorder
132 for (locked_idx, locked) in held.borrow().iter() {
133 if *locked_idx == this.lock_idx {
134 // With `feature = "backtrace"` set, we may be looking at different instances
136 debug_assert!(cfg!(feature = "backtrace"), "Tried to acquire a lock while it was held!");
138 for (locked_dep_idx, _locked_dep) in locked.locked_before.lock().unwrap().iter() {
139 if *locked_dep_idx == this.lock_idx && *locked_dep_idx != locked.lock_idx {
140 #[cfg(feature = "backtrace")]
141 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",
142 get_construction_location(&this._lock_construction_bt), this.lock_idx, this._lock_construction_bt,
143 get_construction_location(&locked._lock_construction_bt), locked.lock_idx, locked._lock_construction_bt,
144 _locked_dep._lockdep_trace);
145 #[cfg(not(feature = "backtrace"))]
146 panic!("Tried to violate existing lockorder. Build with the backtrace feature for more info.");
149 // Insert any already-held locks in our locked-before set.
150 let mut locked_before = this.locked_before.lock().unwrap();
151 if !locked_before.contains_key(&locked.lock_idx) {
152 let lockdep = LockDep { lock: Arc::clone(locked), _lockdep_trace: Backtrace::new() };
153 locked_before.insert(lockdep.lock.lock_idx, lockdep);
156 held.borrow_mut().insert(this.lock_idx, Arc::clone(this));
160 fn held_by_thread(this: &Arc<LockMetadata>) -> LockHeldState {
161 let mut res = LockHeldState::NotHeldByThread;
162 LOCKS_HELD.with(|held| {
163 for (locked_idx, _locked) in held.borrow().iter() {
164 if *locked_idx == this.lock_idx {
165 res = LockHeldState::HeldByThread;
172 fn try_locked(this: &Arc<LockMetadata>) {
173 LOCKS_HELD.with(|held| {
174 // Since a try-lock will simply fail if the lock is held already, we do not
175 // consider try-locks to ever generate lockorder inversions. However, if a try-lock
176 // succeeds, we do consider it to have created lockorder dependencies.
177 let mut locked_before = this.locked_before.lock().unwrap();
178 for (locked_idx, locked) in held.borrow().iter() {
179 if !locked_before.contains_key(locked_idx) {
180 let lockdep = LockDep { lock: Arc::clone(locked), _lockdep_trace: Backtrace::new() };
181 locked_before.insert(*locked_idx, lockdep);
184 held.borrow_mut().insert(this.lock_idx, Arc::clone(this));
189 pub struct Mutex<T: Sized> {
191 deps: Arc<LockMetadata>,
194 #[must_use = "if unused the Mutex will immediately unlock"]
195 pub struct MutexGuard<'a, T: Sized + 'a> {
197 lock: StdMutexGuard<'a, T>,
200 impl<'a, T: Sized> MutexGuard<'a, T> {
201 fn into_inner(self) -> StdMutexGuard<'a, T> {
202 // Somewhat unclear why we cannot move out of self.lock, but doing so gets E0509.
204 let v: StdMutexGuard<'a, T> = std::ptr::read(&self.lock);
205 std::mem::forget(self);
211 impl<T: Sized> Drop for MutexGuard<'_, T> {
213 LOCKS_HELD.with(|held| {
214 held.borrow_mut().remove(&self.mutex.deps.lock_idx);
219 impl<T: Sized> Deref for MutexGuard<'_, T> {
222 fn deref(&self) -> &T {
227 impl<T: Sized> DerefMut for MutexGuard<'_, T> {
228 fn deref_mut(&mut self) -> &mut T {
229 self.lock.deref_mut()
234 pub fn new(inner: T) -> Mutex<T> {
235 Mutex { inner: StdMutex::new(inner), deps: LockMetadata::new() }
238 pub fn lock<'a>(&'a self) -> LockResult<MutexGuard<'a, T>> {
239 LockMetadata::pre_lock(&self.deps);
240 self.inner.lock().map(|lock| MutexGuard { mutex: self, lock }).map_err(|_| ())
243 pub fn try_lock<'a>(&'a self) -> LockResult<MutexGuard<'a, T>> {
244 let res = self.inner.try_lock().map(|lock| MutexGuard { mutex: self, lock }).map_err(|_| ());
246 LockMetadata::try_locked(&self.deps);
252 impl <T> LockTestExt for Mutex<T> {
254 fn held_by_thread(&self) -> LockHeldState {
255 LockMetadata::held_by_thread(&self.deps)
259 pub struct RwLock<T: Sized> {
261 deps: Arc<LockMetadata>,
264 pub struct RwLockReadGuard<'a, T: Sized + 'a> {
266 guard: StdRwLockReadGuard<'a, T>,
269 pub struct RwLockWriteGuard<'a, T: Sized + 'a> {
271 guard: StdRwLockWriteGuard<'a, T>,
274 impl<T: Sized> Deref for RwLockReadGuard<'_, T> {
277 fn deref(&self) -> &T {
282 impl<T: Sized> Drop for RwLockReadGuard<'_, T> {
284 LOCKS_HELD.with(|held| {
285 held.borrow_mut().remove(&self.lock.deps.lock_idx);
290 impl<T: Sized> Deref for RwLockWriteGuard<'_, T> {
293 fn deref(&self) -> &T {
298 impl<T: Sized> Drop for RwLockWriteGuard<'_, T> {
300 LOCKS_HELD.with(|held| {
301 held.borrow_mut().remove(&self.lock.deps.lock_idx);
306 impl<T: Sized> DerefMut for RwLockWriteGuard<'_, T> {
307 fn deref_mut(&mut self) -> &mut T {
308 self.guard.deref_mut()
313 pub fn new(inner: T) -> RwLock<T> {
314 RwLock { inner: StdRwLock::new(inner), deps: LockMetadata::new() }
317 pub fn read<'a>(&'a self) -> LockResult<RwLockReadGuard<'a, T>> {
318 // Note that while we could be taking a recursive read lock here, Rust's `RwLock` may
319 // deadlock trying to take a second read lock if another thread is waiting on the write
320 // lock. Its platform dependent (but our in-tree `FairRwLock` guarantees this behavior).
321 LockMetadata::pre_lock(&self.deps);
322 self.inner.read().map(|guard| RwLockReadGuard { lock: self, guard }).map_err(|_| ())
325 pub fn write<'a>(&'a self) -> LockResult<RwLockWriteGuard<'a, T>> {
326 LockMetadata::pre_lock(&self.deps);
327 self.inner.write().map(|guard| RwLockWriteGuard { lock: self, guard }).map_err(|_| ())
330 pub fn try_write<'a>(&'a self) -> LockResult<RwLockWriteGuard<'a, T>> {
331 let res = self.inner.try_write().map(|guard| RwLockWriteGuard { lock: self, guard }).map_err(|_| ());
333 LockMetadata::try_locked(&self.deps);
339 impl <T> LockTestExt for RwLock<T> {
341 fn held_by_thread(&self) -> LockHeldState {
342 LockMetadata::held_by_thread(&self.deps)
346 pub type FairRwLock<T> = RwLock<T>;