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 pub use std::sync::WaitTimeoutResult;
17 use crate::prelude::HashMap;
19 use super::{LockTestExt, LockHeldState};
21 #[cfg(feature = "backtrace")]
22 use {crate::prelude::hash_map, backtrace::Backtrace, std::sync::Once};
24 #[cfg(not(feature = "backtrace"))]
26 #[cfg(not(feature = "backtrace"))]
27 impl Backtrace { fn new() -> Backtrace { Backtrace {} } }
29 pub type LockResult<Guard> = Result<Guard, ()>;
36 pub fn new() -> Condvar {
37 Condvar { inner: StdCondvar::new() }
40 pub fn wait<'a, T>(&'a self, guard: MutexGuard<'a, T>) -> LockResult<MutexGuard<'a, T>> {
41 let mutex: &'a Mutex<T> = guard.mutex;
42 self.inner.wait(guard.into_inner()).map(|lock| MutexGuard { mutex, lock }).map_err(|_| ())
45 pub fn wait_while<'a, T, F: FnMut(&mut T) -> bool>(&'a self, guard: MutexGuard<'a, T>, condition: F)
46 -> LockResult<MutexGuard<'a, T>> {
47 let mutex: &'a Mutex<T> = guard.mutex;
48 self.inner.wait_while(guard.into_inner(), condition).map(|lock| MutexGuard { mutex, lock })
53 pub fn wait_timeout<'a, T>(&'a self, guard: MutexGuard<'a, T>, dur: Duration) -> LockResult<(MutexGuard<'a, T>, ())> {
54 let mutex = guard.mutex;
55 self.inner.wait_timeout(guard.into_inner(), dur).map(|(lock, _)| (MutexGuard { mutex, lock }, ())).map_err(|_| ())
59 pub fn wait_timeout_while<'a, T, F: FnMut(&mut T) -> bool>(&'a self, guard: MutexGuard<'a, T>, dur: Duration, condition: F)
60 -> LockResult<(MutexGuard<'a, T>, WaitTimeoutResult)> {
61 let mutex = guard.mutex;
62 self.inner.wait_timeout_while(guard.into_inner(), dur, condition).map_err(|_| ())
63 .map(|(lock, e)| (MutexGuard { mutex, lock }, e))
66 pub fn notify_all(&self) { self.inner.notify_all(); }
70 /// We track the set of locks currently held by a reference to their `LockMetadata`
71 static LOCKS_HELD: RefCell<HashMap<u64, Arc<LockMetadata>>> = RefCell::new(HashMap::new());
73 static LOCK_IDX: AtomicUsize = AtomicUsize::new(0);
75 #[cfg(feature = "backtrace")]
76 static mut LOCKS: Option<StdMutex<HashMap<String, Arc<LockMetadata>>>> = None;
77 #[cfg(feature = "backtrace")]
78 static LOCKS_INIT: Once = Once::new();
80 /// Metadata about a single lock, by id, the set of things locked-before it, and the backtrace of
81 /// when the Mutex itself was constructed.
84 locked_before: StdMutex<HashMap<u64, LockDep>>,
85 _lock_construction_bt: Backtrace,
89 lock: Arc<LockMetadata>,
90 /// lockdep_trace is unused unless we're building with `backtrace`, so we mark it _
91 _lockdep_trace: Backtrace,
94 // Locates the frame preceding the earliest `debug_sync` frame in the call stack. This ensures we
95 // can properly detect a lock's construction and acquiral callsites, since the latter may contain
96 // multiple `debug_sync` frames.
97 #[cfg(feature = "backtrace")]
98 fn locate_call_symbol(backtrace: &Backtrace) -> (String, Option<u32>) {
99 // Find the earliest `debug_sync` frame (or that is in our tests) and use the frame preceding it
100 // as the callsite. Note that the first few frames may be in the `backtrace` crate, so we have
102 let sync_mutex_constr_regex = regex::Regex::new(r"lightning.*debug_sync").unwrap();
103 let mut found_debug_sync = false;
104 let mut symbol_after_latest_debug_sync = None;
105 for frame in backtrace.frames().iter() {
106 for symbol in frame.symbols().iter() {
107 if let Some(symbol_name) = symbol.name().map(|name| name.as_str()).flatten() {
108 if !sync_mutex_constr_regex.is_match(symbol_name) {
109 if found_debug_sync {
110 symbol_after_latest_debug_sync = Some(symbol);
111 found_debug_sync = false;
113 } else { found_debug_sync = true; }
117 let symbol = symbol_after_latest_debug_sync.expect("Couldn't find lock call symbol");
118 (format!("{}:{}", symbol.filename().unwrap().display(), symbol.lineno().unwrap()), symbol.colno())
122 fn new() -> Arc<LockMetadata> {
123 let backtrace = Backtrace::new();
124 let lock_idx = LOCK_IDX.fetch_add(1, Ordering::Relaxed) as u64;
126 let res = Arc::new(LockMetadata {
127 locked_before: StdMutex::new(HashMap::new()),
129 _lock_construction_bt: backtrace,
132 #[cfg(feature = "backtrace")]
134 let (lock_constr_location, lock_constr_colno) =
135 locate_call_symbol(&res._lock_construction_bt);
136 LOCKS_INIT.call_once(|| { unsafe { LOCKS = Some(StdMutex::new(HashMap::new())); } });
137 let mut locks = unsafe { LOCKS.as_ref() }.unwrap().lock().unwrap();
138 match locks.entry(lock_constr_location) {
139 hash_map::Entry::Occupied(e) => {
140 assert_eq!(lock_constr_colno,
141 locate_call_symbol(&e.get()._lock_construction_bt).1,
142 "Because Windows doesn't support column number results in backtraces, we cannot construct two mutexes on the same line or we risk lockorder detection false positives.");
143 return Arc::clone(e.get())
145 hash_map::Entry::Vacant(e) => { e.insert(Arc::clone(&res)); },
151 fn pre_lock(this: &Arc<LockMetadata>, _double_lock_self_allowed: bool) {
152 LOCKS_HELD.with(|held| {
153 // For each lock that is currently held, check that no lock's `locked_before` set
154 // includes the lock we're about to hold, which would imply a lockorder inversion.
155 for (locked_idx, _locked) in held.borrow().iter() {
156 if *locked_idx == this.lock_idx {
157 // Note that with `feature = "backtrace"` set, we may be looking at different
158 // instances of the same lock. Still, doing so is quite risky, a total order
159 // must be maintained, and doing so across a set of otherwise-identical mutexes
160 // is fraught with issues.
161 #[cfg(feature = "backtrace")]
162 debug_assert!(_double_lock_self_allowed,
163 "Tried to acquire a lock while it was held!\nLock constructed at {}",
164 locate_call_symbol(&this._lock_construction_bt).0);
165 #[cfg(not(feature = "backtrace"))]
166 panic!("Tried to acquire a lock while it was held!");
169 for (_locked_idx, locked) in held.borrow().iter() {
170 for (locked_dep_idx, _locked_dep) in locked.locked_before.lock().unwrap().iter() {
171 let is_dep_this_lock = *locked_dep_idx == this.lock_idx;
172 let has_same_construction = *locked_dep_idx == locked.lock_idx;
173 if is_dep_this_lock && !has_same_construction {
174 #[allow(unused_mut, unused_assignments)]
175 let mut has_same_callsite = false;
176 #[cfg(feature = "backtrace")] {
177 has_same_callsite = _double_lock_self_allowed &&
178 locate_call_symbol(&_locked_dep._lockdep_trace) ==
179 locate_call_symbol(&Backtrace::new());
181 if !has_same_callsite {
182 #[cfg(feature = "backtrace")]
183 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",
184 locate_call_symbol(&this._lock_construction_bt).0,
185 this.lock_idx, this._lock_construction_bt,
186 locate_call_symbol(&locked._lock_construction_bt).0,
187 locked.lock_idx, locked._lock_construction_bt,
188 _locked_dep._lockdep_trace);
189 #[cfg(not(feature = "backtrace"))]
190 panic!("Tried to violate existing lockorder. Build with the backtrace feature for more info.");
194 // Insert any already-held locks in our locked-before set.
195 let mut locked_before = this.locked_before.lock().unwrap();
196 if !locked_before.contains_key(&locked.lock_idx) {
197 let lockdep = LockDep { lock: Arc::clone(locked), _lockdep_trace: Backtrace::new() };
198 locked_before.insert(lockdep.lock.lock_idx, lockdep);
201 held.borrow_mut().insert(this.lock_idx, Arc::clone(this));
205 fn held_by_thread(this: &Arc<LockMetadata>) -> LockHeldState {
206 let mut res = LockHeldState::NotHeldByThread;
207 LOCKS_HELD.with(|held| {
208 for (locked_idx, _locked) in held.borrow().iter() {
209 if *locked_idx == this.lock_idx {
210 res = LockHeldState::HeldByThread;
217 fn try_locked(this: &Arc<LockMetadata>) {
218 LOCKS_HELD.with(|held| {
219 // Since a try-lock will simply fail if the lock is held already, we do not
220 // consider try-locks to ever generate lockorder inversions. However, if a try-lock
221 // succeeds, we do consider it to have created lockorder dependencies.
222 let mut locked_before = this.locked_before.lock().unwrap();
223 for (locked_idx, locked) in held.borrow().iter() {
224 if !locked_before.contains_key(locked_idx) {
225 let lockdep = LockDep { lock: Arc::clone(locked), _lockdep_trace: Backtrace::new() };
226 locked_before.insert(*locked_idx, lockdep);
229 held.borrow_mut().insert(this.lock_idx, Arc::clone(this));
234 pub struct Mutex<T: Sized> {
236 deps: Arc<LockMetadata>,
238 impl<T: Sized> Mutex<T> {
239 pub(crate) fn into_inner(self) -> LockResult<T> {
240 self.inner.into_inner().map_err(|_| ())
244 #[must_use = "if unused the Mutex will immediately unlock"]
245 pub struct MutexGuard<'a, T: Sized + 'a> {
247 lock: StdMutexGuard<'a, T>,
250 impl<'a, T: Sized> MutexGuard<'a, T> {
251 fn into_inner(self) -> StdMutexGuard<'a, T> {
252 // Somewhat unclear why we cannot move out of self.lock, but doing so gets E0509.
254 let v: StdMutexGuard<'a, T> = std::ptr::read(&self.lock);
255 std::mem::forget(self);
261 impl<T: Sized> Drop for MutexGuard<'_, T> {
263 LOCKS_HELD.with(|held| {
264 held.borrow_mut().remove(&self.mutex.deps.lock_idx);
269 impl<T: Sized> Deref for MutexGuard<'_, T> {
272 fn deref(&self) -> &T {
277 impl<T: Sized> DerefMut for MutexGuard<'_, T> {
278 fn deref_mut(&mut self) -> &mut T {
279 self.lock.deref_mut()
284 pub fn new(inner: T) -> Mutex<T> {
285 Mutex { inner: StdMutex::new(inner), deps: LockMetadata::new() }
288 pub fn lock<'a>(&'a self) -> LockResult<MutexGuard<'a, T>> {
289 LockMetadata::pre_lock(&self.deps, false);
290 self.inner.lock().map(|lock| MutexGuard { mutex: self, lock }).map_err(|_| ())
293 pub fn try_lock<'a>(&'a self) -> LockResult<MutexGuard<'a, T>> {
294 let res = self.inner.try_lock().map(|lock| MutexGuard { mutex: self, lock }).map_err(|_| ());
296 LockMetadata::try_locked(&self.deps);
302 impl<'a, T: 'a> LockTestExt<'a> for Mutex<T> {
304 fn held_by_thread(&self) -> LockHeldState {
305 LockMetadata::held_by_thread(&self.deps)
307 type ExclLock = MutexGuard<'a, T>;
309 fn unsafe_well_ordered_double_lock_self(&'a self) -> MutexGuard<T> {
310 LockMetadata::pre_lock(&self.deps, true);
311 self.inner.lock().map(|lock| MutexGuard { mutex: self, lock }).unwrap()
315 pub struct RwLock<T: Sized> {
317 deps: Arc<LockMetadata>,
320 pub struct RwLockReadGuard<'a, T: Sized + 'a> {
322 guard: StdRwLockReadGuard<'a, T>,
325 pub struct RwLockWriteGuard<'a, T: Sized + 'a> {
327 guard: StdRwLockWriteGuard<'a, T>,
330 impl<T: Sized> Deref for RwLockReadGuard<'_, T> {
333 fn deref(&self) -> &T {
338 impl<T: Sized> Drop for RwLockReadGuard<'_, T> {
340 LOCKS_HELD.with(|held| {
341 held.borrow_mut().remove(&self.lock.deps.lock_idx);
346 impl<T: Sized> Deref for RwLockWriteGuard<'_, T> {
349 fn deref(&self) -> &T {
354 impl<T: Sized> Drop for RwLockWriteGuard<'_, T> {
356 LOCKS_HELD.with(|held| {
357 held.borrow_mut().remove(&self.lock.deps.lock_idx);
362 impl<T: Sized> DerefMut for RwLockWriteGuard<'_, T> {
363 fn deref_mut(&mut self) -> &mut T {
364 self.guard.deref_mut()
369 pub fn new(inner: T) -> RwLock<T> {
370 RwLock { inner: StdRwLock::new(inner), deps: LockMetadata::new() }
373 pub fn read<'a>(&'a self) -> LockResult<RwLockReadGuard<'a, T>> {
374 // Note that while we could be taking a recursive read lock here, Rust's `RwLock` may
375 // deadlock trying to take a second read lock if another thread is waiting on the write
376 // lock. This behavior is platform dependent, but our in-tree `FairRwLock` guarantees
378 LockMetadata::pre_lock(&self.deps, false);
379 self.inner.read().map(|guard| RwLockReadGuard { lock: self, guard }).map_err(|_| ())
382 pub fn write<'a>(&'a self) -> LockResult<RwLockWriteGuard<'a, T>> {
383 LockMetadata::pre_lock(&self.deps, false);
384 self.inner.write().map(|guard| RwLockWriteGuard { lock: self, guard }).map_err(|_| ())
387 pub fn try_write<'a>(&'a self) -> LockResult<RwLockWriteGuard<'a, T>> {
388 let res = self.inner.try_write().map(|guard| RwLockWriteGuard { lock: self, guard }).map_err(|_| ());
390 LockMetadata::try_locked(&self.deps);
396 impl<'a, T: 'a> LockTestExt<'a> for RwLock<T> {
398 fn held_by_thread(&self) -> LockHeldState {
399 LockMetadata::held_by_thread(&self.deps)
401 type ExclLock = RwLockWriteGuard<'a, T>;
403 fn unsafe_well_ordered_double_lock_self(&'a self) -> RwLockWriteGuard<'a, T> {
404 LockMetadata::pre_lock(&self.deps, true);
405 self.inner.write().map(|guard| RwLockWriteGuard { lock: self, guard }).unwrap()
409 pub type FairRwLock<T> = RwLock<T>;