_ Git - rust-lightning/blob - lightning/src/sync/debug_sync.rs

   1 pub use ::alloc::sync::Arc;
   2 use core::ops::{Deref, DerefMut};
   3 use core::time::Duration;
   4
   5 use std::cell::RefCell;
   6
   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;
  14
  15 pub use std::sync::WaitTimeoutResult;
  16
  17 use crate::prelude::HashMap;
  18
  19 use super::{LockTestExt, LockHeldState};
  20
  21 #[cfg(feature = "backtrace")]
  22 use {crate::prelude::hash_map, backtrace::Backtrace, std::sync::Once};
  23
  24 #[cfg(not(feature = "backtrace"))]
  25 struct Backtrace{}
  26 #[cfg(not(feature = "backtrace"))]
  27 impl Backtrace { fn new() -> Backtrace { Backtrace {} } }
  28
  29 pub type LockResult<Guard> = Result<Guard, ()>;
  30
  31 pub struct Condvar {
  32         inner: StdCondvar,
  33 }
  34
  35 impl Condvar {
  36         pub fn new() -> Condvar {
  37                 Condvar { inner: StdCondvar::new() }
  38         }
  39
  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(|_| ())
  43         }
  44
  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 })
  49                         .map_err(|_| ())
  50         }
  51
  52         #[allow(unused)]
  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(|_| ())
  56         }
  57
  58         #[allow(unused)]
  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))
  64         }
  65
  66         pub fn notify_all(&self) { self.inner.notify_all(); }
  67 }
  68
  69 thread_local! {
  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());
  72 }
  73 static LOCK_IDX: AtomicUsize = AtomicUsize::new(0);
  74
  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();
  79
  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.
  82 struct LockMetadata {
  83         lock_idx: u64,
  84         locked_before: StdMutex<HashMap<u64, LockDep>>,
  85         _lock_construction_bt: Backtrace,
  86 }
  87
  88 struct LockDep {
  89         lock: Arc<LockMetadata>,
  90         /// lockdep_trace is unused unless we're building with `backtrace`, so we mark it _
  91         _lockdep_trace: Backtrace,
  92 }
  93
  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
 101         // to ignore those.
 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;
 112                                         }
 113                                 } else { found_debug_sync = true; }
 114                         }
 115                 }
 116         }
 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())
 119 }
 120
 121 impl LockMetadata {
 122         fn new() -> Arc<LockMetadata> {
 123                 let backtrace = Backtrace::new();
 124                 let lock_idx = LOCK_IDX.fetch_add(1, Ordering::Relaxed) as u64;
 125
 126                 let res = Arc::new(LockMetadata {
 127                         locked_before: StdMutex::new(HashMap::new()),
 128                         lock_idx,
 129                         _lock_construction_bt: backtrace,
 130                 });
 131
 132                 #[cfg(feature = "backtrace")]
 133                 {
 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())
 144                                 },
 145                                 hash_map::Entry::Vacant(e) => { e.insert(Arc::clone(&res)); },
 146                         }
 147                 }
 148                 res
 149         }
 150
 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!");
 167                                 }
 168                         }
 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());
 180                                                 }
 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.");
 191                                                 }
 192                                         }
 193                                 }
 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);
 199                                 }
 200                         }
 201                         held.borrow_mut().insert(this.lock_idx, Arc::clone(this));
 202                 });
 203         }
 204
 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;
 211                                 }
 212                         }
 213                 });
 214                 res
 215         }
 216
 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);
 227                                 }
 228                         }
 229                         held.borrow_mut().insert(this.lock_idx, Arc::clone(this));
 230                 });
 231         }
 232 }
 233
 234 pub struct Mutex<T: Sized> {
 235         inner: StdMutex<T>,
 236         deps: Arc<LockMetadata>,
 237 }
 238 impl<T: Sized> Mutex<T> {
 239         pub(crate) fn into_inner(self) -> LockResult<T> {
 240                 self.inner.into_inner().map_err(|_| ())
 241         }
 242 }
 243
 244 #[must_use = "if unused the Mutex will immediately unlock"]
 245 pub struct MutexGuard<'a, T: Sized + 'a> {
 246         mutex: &'a Mutex<T>,
 247         lock: StdMutexGuard<'a, T>,
 248 }
 249
 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.
 253                 unsafe {
 254                         let v: StdMutexGuard<'a, T> = std::ptr::read(&self.lock);
 255                         std::mem::forget(self);
 256                         v
 257                 }
 258         }
 259 }
 260
 261 impl<T: Sized> Drop for MutexGuard<'_, T> {
 262         fn drop(&mut self) {
 263                 LOCKS_HELD.with(|held| {
 264                         held.borrow_mut().remove(&self.mutex.deps.lock_idx);
 265                 });
 266         }
 267 }
 268
 269 impl<T: Sized> Deref for MutexGuard<'_, T> {
 270         type Target = T;
 271
 272         fn deref(&self) -> &T {
 273                 &self.lock.deref()
 274         }
 275 }
 276
 277 impl<T: Sized> DerefMut for MutexGuard<'_, T> {
 278         fn deref_mut(&mut self) -> &mut T {
 279                 self.lock.deref_mut()
 280         }
 281 }
 282
 283 impl<T> Mutex<T> {
 284         pub fn new(inner: T) -> Mutex<T> {
 285                 Mutex { inner: StdMutex::new(inner), deps: LockMetadata::new() }
 286         }
 287
 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(|_| ())
 291         }
 292
 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(|_| ());
 295                 if res.is_ok() {
 296                         LockMetadata::try_locked(&self.deps);
 297                 }
 298                 res
 299         }
 300 }
 301
 302 impl<'a, T: 'a> LockTestExt<'a> for Mutex<T> {
 303         #[inline]
 304         fn held_by_thread(&self) -> LockHeldState {
 305                 LockMetadata::held_by_thread(&self.deps)
 306         }
 307         type ExclLock = MutexGuard<'a, T>;
 308         #[inline]
 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()
 312         }
 313 }
 314
 315 pub struct RwLock<T: Sized> {
 316         inner: StdRwLock<T>,
 317         deps: Arc<LockMetadata>,
 318 }
 319
 320 pub struct RwLockReadGuard<'a, T: Sized + 'a> {
 321         lock: &'a RwLock<T>,
 322         guard: StdRwLockReadGuard<'a, T>,
 323 }
 324
 325 pub struct RwLockWriteGuard<'a, T: Sized + 'a> {
 326         lock: &'a RwLock<T>,
 327         guard: StdRwLockWriteGuard<'a, T>,
 328 }
 329
 330 impl<T: Sized> Deref for RwLockReadGuard<'_, T> {
 331         type Target = T;
 332
 333         fn deref(&self) -> &T {
 334                 &self.guard.deref()
 335         }
 336 }
 337
 338 impl<T: Sized> Drop for RwLockReadGuard<'_, T> {
 339         fn drop(&mut self) {
 340                 LOCKS_HELD.with(|held| {
 341                         held.borrow_mut().remove(&self.lock.deps.lock_idx);
 342                 });
 343         }
 344 }
 345
 346 impl<T: Sized> Deref for RwLockWriteGuard<'_, T> {
 347         type Target = T;
 348
 349         fn deref(&self) -> &T {
 350                 &self.guard.deref()
 351         }
 352 }
 353
 354 impl<T: Sized> Drop for RwLockWriteGuard<'_, T> {
 355         fn drop(&mut self) {
 356                 LOCKS_HELD.with(|held| {
 357                         held.borrow_mut().remove(&self.lock.deps.lock_idx);
 358                 });
 359         }
 360 }
 361
 362 impl<T: Sized> DerefMut for RwLockWriteGuard<'_, T> {
 363         fn deref_mut(&mut self) -> &mut T {
 364                 self.guard.deref_mut()
 365         }
 366 }
 367
 368 impl<T> RwLock<T> {
 369         pub fn new(inner: T) -> RwLock<T> {
 370                 RwLock { inner: StdRwLock::new(inner), deps: LockMetadata::new() }
 371         }
 372
 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
 377                 // such a deadlock.
 378                 LockMetadata::pre_lock(&self.deps, false);
 379                 self.inner.read().map(|guard| RwLockReadGuard { lock: self, guard }).map_err(|_| ())
 380         }
 381
 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(|_| ())
 385         }
 386
 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(|_| ());
 389                 if res.is_ok() {
 390                         LockMetadata::try_locked(&self.deps);
 391                 }
 392                 res
 393         }
 394 }
 395
 396 impl<'a, T: 'a> LockTestExt<'a> for RwLock<T> {
 397         #[inline]
 398         fn held_by_thread(&self) -> LockHeldState {
 399                 LockMetadata::held_by_thread(&self.deps)
 400         }
 401         type ExclLock = RwLockWriteGuard<'a, T>;
 402         #[inline]
 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()
 406         }
 407 }
 408
 409 pub type FairRwLock<T> = RwLock<T>;