_ Git - rust-lightning/blob - lightning/src/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 use prelude::HashMap;
  16
  17 #[cfg(feature = "backtrace")]
  18 use {prelude::hash_map, backtrace::Backtrace, std::sync::Once};
  19
  20 #[cfg(not(feature = "backtrace"))]
  21 struct Backtrace{}
  22 #[cfg(not(feature = "backtrace"))]
  23 impl Backtrace { fn new() -> Backtrace { Backtrace {} } }
  24
  25 pub type LockResult<Guard> = Result<Guard, ()>;
  26
  27 pub struct Condvar {
  28         inner: StdCondvar,
  29 }
  30
  31 impl Condvar {
  32         pub fn new() -> Condvar {
  33                 Condvar { inner: StdCondvar::new() }
  34         }
  35
  36         pub fn wait<'a, T>(&'a self, guard: MutexGuard<'a, T>) -> LockResult<MutexGuard<'a, T>> {
  37                 let mutex: &'a Mutex<T> = guard.mutex;
  38                 self.inner.wait(guard.into_inner()).map(|lock| MutexGuard { mutex, lock }).map_err(|_| ())
  39         }
  40
  41         #[allow(unused)]
  42         pub fn wait_timeout<'a, T>(&'a self, guard: MutexGuard<'a, T>, dur: Duration) -> LockResult<(MutexGuard<'a, T>, ())> {
  43                 let mutex = guard.mutex;
  44                 self.inner.wait_timeout(guard.into_inner(), dur).map(|(lock, _)| (MutexGuard { mutex, lock }, ())).map_err(|_| ())
  45         }
  46
  47         pub fn notify_all(&self) { self.inner.notify_all(); }
  48 }
  49
  50 thread_local! {
  51         /// We track the set of locks currently held by a reference to their `LockMetadata`
  52         static LOCKS_HELD: RefCell<HashMap<u64, Arc<LockMetadata>>> = RefCell::new(HashMap::new());
  53 }
  54 static LOCK_IDX: AtomicUsize = AtomicUsize::new(0);
  55
  56 #[cfg(feature = "backtrace")]
  57 static mut LOCKS: Option<StdMutex<HashMap<String, Arc<LockMetadata>>>> = None;
  58 #[cfg(feature = "backtrace")]
  59 static LOCKS_INIT: Once = Once::new();
  60
  61 /// Metadata about a single lock, by id, the set of things locked-before it, and the backtrace of
  62 /// when the Mutex itself was constructed.
  63 struct LockMetadata {
  64         lock_idx: u64,
  65         locked_before: StdMutex<HashMap<u64, LockDep>>,
  66         _lock_construction_bt: Backtrace,
  67 }
  68
  69 struct LockDep {
  70         lock: Arc<LockMetadata>,
  71         lockdep_trace: Backtrace,
  72 }
  73
  74 #[cfg(feature = "backtrace")]
  75 fn get_construction_location(backtrace: &Backtrace) -> String {
  76         // Find the first frame that is after `debug_sync` (or that is in our tests) and use
  77         // that as the mutex construction site. Note that the first few frames may be in
  78         // the `backtrace` crate, so we have to ignore those.
  79         let sync_mutex_constr_regex = regex::Regex::new(r"lightning.*debug_sync.*new").unwrap();
  80         let mut found_debug_sync = false;
  81         for frame in backtrace.frames() {
  82                 for symbol in frame.symbols() {
  83                         let symbol_name = symbol.name().unwrap().as_str().unwrap();
  84                         if !sync_mutex_constr_regex.is_match(symbol_name) {
  85                                 if found_debug_sync {
  86                                         if let Some(col) = symbol.colno() {
  87                                                 return format!("{}:{}:{}", symbol.filename().unwrap().display(), symbol.lineno().unwrap(), col);
  88                                         } else {
  89                                                 // Windows debug symbols don't support column numbers, so fall back to
  90                                                 // line numbers only if no `colno` is available
  91                                                 return format!("{}:{}", symbol.filename().unwrap().display(), symbol.lineno().unwrap());
  92                                         }
  93                                 }
  94                         } else { found_debug_sync = true; }
  95                 }
  96         }
  97         panic!("Couldn't find mutex construction callsite");
  98 }
  99
 100 impl LockMetadata {
 101         fn new() -> Arc<LockMetadata> {
 102                 let backtrace = Backtrace::new();
 103                 let lock_idx = LOCK_IDX.fetch_add(1, Ordering::Relaxed) as u64;
 104
 105                 let res = Arc::new(LockMetadata {
 106                         locked_before: StdMutex::new(HashMap::new()),
 107                         lock_idx,
 108                         _lock_construction_bt: backtrace,
 109                 });
 110
 111                 #[cfg(feature = "backtrace")]
 112                 {
 113                         let lock_constr_location = get_construction_location(&res._lock_construction_bt);
 114                         LOCKS_INIT.call_once(|| { unsafe { LOCKS = Some(StdMutex::new(HashMap::new())); } });
 115                         let mut locks = unsafe { LOCKS.as_ref() }.unwrap().lock().unwrap();
 116                         match locks.entry(lock_constr_location) {
 117                                 hash_map::Entry::Occupied(e) => return Arc::clone(e.get()),
 118                                 hash_map::Entry::Vacant(e) => { e.insert(Arc::clone(&res)); },
 119                         }
 120                 }
 121                 res
 122         }
 123
 124         // Returns whether we were a recursive lock (only relevant for read)
 125         fn _pre_lock(this: &Arc<LockMetadata>, read: bool) -> bool {
 126                 let mut inserted = false;
 127                 LOCKS_HELD.with(|held| {
 128                         // For each lock which is currently locked, check that no lock's locked-before
 129                         // set includes the lock we're about to lock, which would imply a lockorder
 130                         // inversion.
 131                         for (locked_idx, _locked) in held.borrow().iter() {
 132                                 if read && *locked_idx == this.lock_idx {
 133                                         // Recursive read locks are explicitly allowed
 134                                         return;
 135                                 }
 136                         }
 137                         for (locked_idx, locked) in held.borrow().iter() {
 138                                 if !read && *locked_idx == this.lock_idx {
 139                                         // With `feature = "backtrace"` set, we may be looking at different instances
 140                                         // of the same lock.
 141                                         debug_assert!(cfg!(feature = "backtrace"), "Tried to acquire a lock while it was held!");
 142                                 }
 143                                 for (locked_dep_idx, locked_dep) in locked.locked_before.lock().unwrap().iter() {
 144                                         if *locked_dep_idx == this.lock_idx && *locked_dep_idx != locked.lock_idx {
 145                                                 #[cfg(feature = "backtrace")]
 146                                                 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",
 147                                                         get_construction_location(&this._lock_construction_bt), this.lock_idx, this._lock_construction_bt,
 148                                                         get_construction_location(&locked._lock_construction_bt), locked.lock_idx, locked._lock_construction_bt,
 149                                                         locked_dep.lockdep_trace);
 150                                                 #[cfg(not(feature = "backtrace"))]
 151                                                 panic!("Tried to violate existing lockorder. Build with the backtrace feature for more info.");
 152                                         }
 153                                 }
 154                                 // Insert any already-held locks in our locked-before set.
 155                                 let mut locked_before = this.locked_before.lock().unwrap();
 156                                 if !locked_before.contains_key(&locked.lock_idx) {
 157                                         let lockdep = LockDep { lock: Arc::clone(locked), lockdep_trace: Backtrace::new() };
 158                                         locked_before.insert(lockdep.lock.lock_idx, lockdep);
 159                                 }
 160                         }
 161                         held.borrow_mut().insert(this.lock_idx, Arc::clone(this));
 162                         inserted = true;
 163                 });
 164                 inserted
 165         }
 166
 167         fn pre_lock(this: &Arc<LockMetadata>) { Self::_pre_lock(this, false); }
 168         fn pre_read_lock(this: &Arc<LockMetadata>) -> bool { Self::_pre_lock(this, true) }
 169
 170         fn try_locked(this: &Arc<LockMetadata>) {
 171                 LOCKS_HELD.with(|held| {
 172                         // Since a try-lock will simply fail if the lock is held already, we do not
 173                         // consider try-locks to ever generate lockorder inversions. However, if a try-lock
 174                         // succeeds, we do consider it to have created lockorder dependencies.
 175                         let mut locked_before = this.locked_before.lock().unwrap();
 176                         for (locked_idx, locked) in held.borrow().iter() {
 177                                 if !locked_before.contains_key(locked_idx) {
 178                                         let lockdep = LockDep { lock: Arc::clone(locked), lockdep_trace: Backtrace::new() };
 179                                         locked_before.insert(*locked_idx, lockdep);
 180                                 }
 181                         }
 182                         held.borrow_mut().insert(this.lock_idx, Arc::clone(this));
 183                 });
 184         }
 185 }
 186
 187 pub struct Mutex<T: Sized> {
 188         inner: StdMutex<T>,
 189         deps: Arc<LockMetadata>,
 190 }
 191
 192 #[must_use = "if unused the Mutex will immediately unlock"]
 193 pub struct MutexGuard<'a, T: Sized + 'a> {
 194         mutex: &'a Mutex<T>,
 195         lock: StdMutexGuard<'a, T>,
 196 }
 197
 198 impl<'a, T: Sized> MutexGuard<'a, T> {
 199         fn into_inner(self) -> StdMutexGuard<'a, T> {
 200                 // Somewhat unclear why we cannot move out of self.lock, but doing so gets E0509.
 201                 unsafe {
 202                         let v: StdMutexGuard<'a, T> = std::ptr::read(&self.lock);
 203                         std::mem::forget(self);
 204                         v
 205                 }
 206         }
 207 }
 208
 209 impl<T: Sized> Drop for MutexGuard<'_, T> {
 210         fn drop(&mut self) {
 211                 LOCKS_HELD.with(|held| {
 212                         held.borrow_mut().remove(&self.mutex.deps.lock_idx);
 213                 });
 214         }
 215 }
 216
 217 impl<T: Sized> Deref for MutexGuard<'_, T> {
 218         type Target = T;
 219
 220         fn deref(&self) -> &T {
 221                 &self.lock.deref()
 222         }
 223 }
 224
 225 impl<T: Sized> DerefMut for MutexGuard<'_, T> {
 226         fn deref_mut(&mut self) -> &mut T {
 227                 self.lock.deref_mut()
 228         }
 229 }
 230
 231 impl<T> Mutex<T> {
 232         pub fn new(inner: T) -> Mutex<T> {
 233                 Mutex { inner: StdMutex::new(inner), deps: LockMetadata::new() }
 234         }
 235
 236         pub fn lock<'a>(&'a self) -> LockResult<MutexGuard<'a, T>> {
 237                 LockMetadata::pre_lock(&self.deps);
 238                 self.inner.lock().map(|lock| MutexGuard { mutex: self, lock }).map_err(|_| ())
 239         }
 240
 241         pub fn try_lock<'a>(&'a self) -> LockResult<MutexGuard<'a, T>> {
 242                 let res = self.inner.try_lock().map(|lock| MutexGuard { mutex: self, lock }).map_err(|_| ());
 243                 if res.is_ok() {
 244                         LockMetadata::try_locked(&self.deps);
 245                 }
 246                 res
 247         }
 248 }
 249
 250 pub struct RwLock<T: Sized> {
 251         inner: StdRwLock<T>,
 252         deps: Arc<LockMetadata>,
 253 }
 254
 255 pub struct RwLockReadGuard<'a, T: Sized + 'a> {
 256         lock: &'a RwLock<T>,
 257         first_lock: bool,
 258         guard: StdRwLockReadGuard<'a, T>,
 259 }
 260
 261 pub struct RwLockWriteGuard<'a, T: Sized + 'a> {
 262         lock: &'a RwLock<T>,
 263         guard: StdRwLockWriteGuard<'a, T>,
 264 }
 265
 266 impl<T: Sized> Deref for RwLockReadGuard<'_, T> {
 267         type Target = T;
 268
 269         fn deref(&self) -> &T {
 270                 &self.guard.deref()
 271         }
 272 }
 273
 274 impl<T: Sized> Drop for RwLockReadGuard<'_, T> {
 275         fn drop(&mut self) {
 276                 if !self.first_lock {
 277                         // Note that its not strictly true that the first taken read lock will get unlocked
 278                         // last, but in practice our locks are always taken as RAII, so it should basically
 279                         // always be true.
 280                         return;
 281                 }
 282                 LOCKS_HELD.with(|held| {
 283                         held.borrow_mut().remove(&self.lock.deps.lock_idx);
 284                 });
 285         }
 286 }
 287
 288 impl<T: Sized> Deref for RwLockWriteGuard<'_, T> {
 289         type Target = T;
 290
 291         fn deref(&self) -> &T {
 292                 &self.guard.deref()
 293         }
 294 }
 295
 296 impl<T: Sized> Drop for RwLockWriteGuard<'_, T> {
 297         fn drop(&mut self) {
 298                 LOCKS_HELD.with(|held| {
 299                         held.borrow_mut().remove(&self.lock.deps.lock_idx);
 300                 });
 301         }
 302 }
 303
 304 impl<T: Sized> DerefMut for RwLockWriteGuard<'_, T> {
 305         fn deref_mut(&mut self) -> &mut T {
 306                 self.guard.deref_mut()
 307         }
 308 }
 309
 310 impl<T> RwLock<T> {
 311         pub fn new(inner: T) -> RwLock<T> {
 312                 RwLock { inner: StdRwLock::new(inner), deps: LockMetadata::new() }
 313         }
 314
 315         pub fn read<'a>(&'a self) -> LockResult<RwLockReadGuard<'a, T>> {
 316                 let first_lock = LockMetadata::pre_read_lock(&self.deps);
 317                 self.inner.read().map(|guard| RwLockReadGuard { lock: self, guard, first_lock }).map_err(|_| ())
 318         }
 319
 320         pub fn write<'a>(&'a self) -> LockResult<RwLockWriteGuard<'a, T>> {
 321                 LockMetadata::pre_lock(&self.deps);
 322                 self.inner.write().map(|guard| RwLockWriteGuard { lock: self, guard }).map_err(|_| ())
 323         }
 324
 325         pub fn try_write<'a>(&'a self) -> LockResult<RwLockWriteGuard<'a, T>> {
 326                 let res = self.inner.try_write().map(|guard| RwLockWriteGuard { lock: self, guard }).map_err(|_| ());
 327                 if res.is_ok() {
 328                         LockMetadata::try_locked(&self.deps);
 329                 }
 330                 res
 331         }
 332 }
 333
 334 pub type FairRwLock<T> = RwLock<T>;
 335
 336 mod tests {
 337         use super::{RwLock, Mutex};
 338
 339         #[test]
 340         #[should_panic]
 341         #[cfg(not(feature = "backtrace"))]
 342         fn recursive_lock_fail() {
 343                 let mutex = Mutex::new(());
 344                 let _a = mutex.lock().unwrap();
 345                 let _b = mutex.lock().unwrap();
 346         }
 347
 348         #[test]
 349         fn recursive_read() {
 350                 let lock = RwLock::new(());
 351                 let _a = lock.read().unwrap();
 352                 let _b = lock.read().unwrap();
 353         }
 354
 355         #[test]
 356         #[should_panic]
 357         fn lockorder_fail() {
 358                 let a = Mutex::new(());
 359                 let b = Mutex::new(());
 360                 {
 361                         let _a = a.lock().unwrap();
 362                         let _b = b.lock().unwrap();
 363                 }
 364                 {
 365                         let _b = b.lock().unwrap();
 366                         let _a = a.lock().unwrap();
 367                 }
 368         }
 369
 370         #[test]
 371         #[should_panic]
 372         fn write_lockorder_fail() {
 373                 let a = RwLock::new(());
 374                 let b = RwLock::new(());
 375                 {
 376                         let _a = a.write().unwrap();
 377                         let _b = b.write().unwrap();
 378                 }
 379                 {
 380                         let _b = b.write().unwrap();
 381                         let _a = a.write().unwrap();
 382                 }
 383         }
 384
 385         #[test]
 386         #[should_panic]
 387         fn read_lockorder_fail() {
 388                 let a = RwLock::new(());
 389                 let b = RwLock::new(());
 390                 {
 391                         let _a = a.read().unwrap();
 392                         let _b = b.read().unwrap();
 393                 }
 394                 {
 395                         let _b = b.read().unwrap();
 396                         let _a = a.read().unwrap();
 397                 }
 398         }
 399
 400         #[test]
 401         fn read_recursive_no_lockorder() {
 402                 // Like the above, but note that no lockorder is implied when we recursively read-lock a
 403                 // RwLock, causing this to pass just fine.
 404                 let a = RwLock::new(());
 405                 let b = RwLock::new(());
 406                 let _outer = a.read().unwrap();
 407                 {
 408                         let _a = a.read().unwrap();
 409                         let _b = b.read().unwrap();
 410                 }
 411                 {
 412                         let _b = b.read().unwrap();
 413                         let _a = a.read().unwrap();
 414                 }
 415         }
 416
 417         #[test]
 418         #[should_panic]
 419         fn read_write_lockorder_fail() {
 420                 let a = RwLock::new(());
 421                 let b = RwLock::new(());
 422                 {
 423                         let _a = a.write().unwrap();
 424                         let _b = b.read().unwrap();
 425                 }
 426                 {
 427                         let _b = b.read().unwrap();
 428                         let _a = a.write().unwrap();
 429                 }
 430         }
 431 }