_ 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 is unused unless we're building with `backtrace`, so we mark it _
  72         _lockdep_trace: Backtrace,
  73 }
  74
  75 #[cfg(feature = "backtrace")]
  76 fn get_construction_location(backtrace: &Backtrace) -> String {
  77         // Find the first frame that is after `debug_sync` (or that is in our tests) and use
  78         // that as the mutex construction site. Note that the first few frames may be in
  79         // the `backtrace` crate, so we have to ignore those.
  80         let sync_mutex_constr_regex = regex::Regex::new(r"lightning.*debug_sync.*new").unwrap();
  81         let mut found_debug_sync = false;
  82         for frame in backtrace.frames() {
  83                 for symbol in frame.symbols() {
  84                         let symbol_name = symbol.name().unwrap().as_str().unwrap();
  85                         if !sync_mutex_constr_regex.is_match(symbol_name) {
  86                                 if found_debug_sync {
  87                                         if let Some(col) = symbol.colno() {
  88                                                 return format!("{}:{}:{}", symbol.filename().unwrap().display(), symbol.lineno().unwrap(), col);
  89                                         } else {
  90                                                 // Windows debug symbols don't support column numbers, so fall back to
  91                                                 // line numbers only if no `colno` is available
  92                                                 return format!("{}:{}", symbol.filename().unwrap().display(), symbol.lineno().unwrap());
  93                                         }
  94                                 }
  95                         } else { found_debug_sync = true; }
  96                 }
  97         }
  98         panic!("Couldn't find mutex construction callsite");
  99 }
 100
 101 impl LockMetadata {
 102         fn new() -> Arc<LockMetadata> {
 103                 let backtrace = Backtrace::new();
 104                 let lock_idx = LOCK_IDX.fetch_add(1, Ordering::Relaxed) as u64;
 105
 106                 let res = Arc::new(LockMetadata {
 107                         locked_before: StdMutex::new(HashMap::new()),
 108                         lock_idx,
 109                         _lock_construction_bt: backtrace,
 110                 });
 111
 112                 #[cfg(feature = "backtrace")]
 113                 {
 114                         let lock_constr_location = get_construction_location(&res._lock_construction_bt);
 115                         LOCKS_INIT.call_once(|| { unsafe { LOCKS = Some(StdMutex::new(HashMap::new())); } });
 116                         let mut locks = unsafe { LOCKS.as_ref() }.unwrap().lock().unwrap();
 117                         match locks.entry(lock_constr_location) {
 118                                 hash_map::Entry::Occupied(e) => return Arc::clone(e.get()),
 119                                 hash_map::Entry::Vacant(e) => { e.insert(Arc::clone(&res)); },
 120                         }
 121                 }
 122                 res
 123         }
 124
 125         // Returns whether we were a recursive lock (only relevant for read)
 126         fn _pre_lock(this: &Arc<LockMetadata>, read: bool) -> bool {
 127                 let mut inserted = false;
 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
 131                         // inversion.
 132                         for (locked_idx, _locked) in held.borrow().iter() {
 133                                 if read && *locked_idx == this.lock_idx {
 134                                         // Recursive read locks are explicitly allowed
 135                                         return;
 136                                 }
 137                         }
 138                         for (locked_idx, locked) in held.borrow().iter() {
 139                                 if !read && *locked_idx == this.lock_idx {
 140                                         // With `feature = "backtrace"` set, we may be looking at different instances
 141                                         // of the same lock.
 142                                         debug_assert!(cfg!(feature = "backtrace"), "Tried to acquire a lock while it was held!");
 143                                 }
 144                                 for (locked_dep_idx, _locked_dep) in locked.locked_before.lock().unwrap().iter() {
 145                                         if *locked_dep_idx == this.lock_idx && *locked_dep_idx != locked.lock_idx {
 146                                                 #[cfg(feature = "backtrace")]
 147                                                 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",
 148                                                         get_construction_location(&this._lock_construction_bt), this.lock_idx, this._lock_construction_bt,
 149                                                         get_construction_location(&locked._lock_construction_bt), locked.lock_idx, locked._lock_construction_bt,
 150                                                         _locked_dep._lockdep_trace);
 151                                                 #[cfg(not(feature = "backtrace"))]
 152                                                 panic!("Tried to violate existing lockorder. Build with the backtrace feature for more info.");
 153                                         }
 154                                 }
 155                                 // Insert any already-held locks in our locked-before set.
 156                                 let mut locked_before = this.locked_before.lock().unwrap();
 157                                 if !locked_before.contains_key(&locked.lock_idx) {
 158                                         let lockdep = LockDep { lock: Arc::clone(locked), _lockdep_trace: Backtrace::new() };
 159                                         locked_before.insert(lockdep.lock.lock_idx, lockdep);
 160                                 }
 161                         }
 162                         held.borrow_mut().insert(this.lock_idx, Arc::clone(this));
 163                         inserted = true;
 164                 });
 165                 inserted
 166         }
 167
 168         fn pre_lock(this: &Arc<LockMetadata>) { Self::_pre_lock(this, false); }
 169         fn pre_read_lock(this: &Arc<LockMetadata>) -> bool { Self::_pre_lock(this, true) }
 170
 171         fn try_locked(this: &Arc<LockMetadata>) {
 172                 LOCKS_HELD.with(|held| {
 173                         // Since a try-lock will simply fail if the lock is held already, we do not
 174                         // consider try-locks to ever generate lockorder inversions. However, if a try-lock
 175                         // succeeds, we do consider it to have created lockorder dependencies.
 176                         let mut locked_before = this.locked_before.lock().unwrap();
 177                         for (locked_idx, locked) in held.borrow().iter() {
 178                                 if !locked_before.contains_key(locked_idx) {
 179                                         let lockdep = LockDep { lock: Arc::clone(locked), _lockdep_trace: Backtrace::new() };
 180                                         locked_before.insert(*locked_idx, lockdep);
 181                                 }
 182                         }
 183                         held.borrow_mut().insert(this.lock_idx, Arc::clone(this));
 184                 });
 185         }
 186 }
 187
 188 pub struct Mutex<T: Sized> {
 189         inner: StdMutex<T>,
 190         deps: Arc<LockMetadata>,
 191 }
 192
 193 #[must_use = "if unused the Mutex will immediately unlock"]
 194 pub struct MutexGuard<'a, T: Sized + 'a> {
 195         mutex: &'a Mutex<T>,
 196         lock: StdMutexGuard<'a, T>,
 197 }
 198
 199 impl<'a, T: Sized> MutexGuard<'a, T> {
 200         fn into_inner(self) -> StdMutexGuard<'a, T> {
 201                 // Somewhat unclear why we cannot move out of self.lock, but doing so gets E0509.
 202                 unsafe {
 203                         let v: StdMutexGuard<'a, T> = std::ptr::read(&self.lock);
 204                         std::mem::forget(self);
 205                         v
 206                 }
 207         }
 208 }
 209
 210 impl<T: Sized> Drop for MutexGuard<'_, T> {
 211         fn drop(&mut self) {
 212                 LOCKS_HELD.with(|held| {
 213                         held.borrow_mut().remove(&self.mutex.deps.lock_idx);
 214                 });
 215         }
 216 }
 217
 218 impl<T: Sized> Deref for MutexGuard<'_, T> {
 219         type Target = T;
 220
 221         fn deref(&self) -> &T {
 222                 &self.lock.deref()
 223         }
 224 }
 225
 226 impl<T: Sized> DerefMut for MutexGuard<'_, T> {
 227         fn deref_mut(&mut self) -> &mut T {
 228                 self.lock.deref_mut()
 229         }
 230 }
 231
 232 impl<T> Mutex<T> {
 233         pub fn new(inner: T) -> Mutex<T> {
 234                 Mutex { inner: StdMutex::new(inner), deps: LockMetadata::new() }
 235         }
 236
 237         pub fn lock<'a>(&'a self) -> LockResult<MutexGuard<'a, T>> {
 238                 LockMetadata::pre_lock(&self.deps);
 239                 self.inner.lock().map(|lock| MutexGuard { mutex: self, lock }).map_err(|_| ())
 240         }
 241
 242         pub fn try_lock<'a>(&'a self) -> LockResult<MutexGuard<'a, T>> {
 243                 let res = self.inner.try_lock().map(|lock| MutexGuard { mutex: self, lock }).map_err(|_| ());
 244                 if res.is_ok() {
 245                         LockMetadata::try_locked(&self.deps);
 246                 }
 247                 res
 248         }
 249 }
 250
 251 pub struct RwLock<T: Sized> {
 252         inner: StdRwLock<T>,
 253         deps: Arc<LockMetadata>,
 254 }
 255
 256 pub struct RwLockReadGuard<'a, T: Sized + 'a> {
 257         lock: &'a RwLock<T>,
 258         first_lock: bool,
 259         guard: StdRwLockReadGuard<'a, T>,
 260 }
 261
 262 pub struct RwLockWriteGuard<'a, T: Sized + 'a> {
 263         lock: &'a RwLock<T>,
 264         guard: StdRwLockWriteGuard<'a, T>,
 265 }
 266
 267 impl<T: Sized> Deref for RwLockReadGuard<'_, T> {
 268         type Target = T;
 269
 270         fn deref(&self) -> &T {
 271                 &self.guard.deref()
 272         }
 273 }
 274
 275 impl<T: Sized> Drop for RwLockReadGuard<'_, T> {
 276         fn drop(&mut self) {
 277                 if !self.first_lock {
 278                         // Note that its not strictly true that the first taken read lock will get unlocked
 279                         // last, but in practice our locks are always taken as RAII, so it should basically
 280                         // always be true.
 281                         return;
 282                 }
 283                 LOCKS_HELD.with(|held| {
 284                         held.borrow_mut().remove(&self.lock.deps.lock_idx);
 285                 });
 286         }
 287 }
 288
 289 impl<T: Sized> Deref for RwLockWriteGuard<'_, T> {
 290         type Target = T;
 291
 292         fn deref(&self) -> &T {
 293                 &self.guard.deref()
 294         }
 295 }
 296
 297 impl<T: Sized> Drop for RwLockWriteGuard<'_, T> {
 298         fn drop(&mut self) {
 299                 LOCKS_HELD.with(|held| {
 300                         held.borrow_mut().remove(&self.lock.deps.lock_idx);
 301                 });
 302         }
 303 }
 304
 305 impl<T: Sized> DerefMut for RwLockWriteGuard<'_, T> {
 306         fn deref_mut(&mut self) -> &mut T {
 307                 self.guard.deref_mut()
 308         }
 309 }
 310
 311 impl<T> RwLock<T> {
 312         pub fn new(inner: T) -> RwLock<T> {
 313                 RwLock { inner: StdRwLock::new(inner), deps: LockMetadata::new() }
 314         }
 315
 316         pub fn read<'a>(&'a self) -> LockResult<RwLockReadGuard<'a, T>> {
 317                 let first_lock = LockMetadata::pre_read_lock(&self.deps);
 318                 self.inner.read().map(|guard| RwLockReadGuard { lock: self, guard, first_lock }).map_err(|_| ())
 319         }
 320
 321         pub fn write<'a>(&'a self) -> LockResult<RwLockWriteGuard<'a, T>> {
 322                 LockMetadata::pre_lock(&self.deps);
 323                 self.inner.write().map(|guard| RwLockWriteGuard { lock: self, guard }).map_err(|_| ())
 324         }
 325
 326         pub fn try_write<'a>(&'a self) -> LockResult<RwLockWriteGuard<'a, T>> {
 327                 let res = self.inner.try_write().map(|guard| RwLockWriteGuard { lock: self, guard }).map_err(|_| ());
 328                 if res.is_ok() {
 329                         LockMetadata::try_locked(&self.deps);
 330                 }
 331                 res
 332         }
 333 }
 334
 335 pub type FairRwLock<T> = RwLock<T>;
 336
 337 mod tests {
 338         use super::{RwLock, Mutex};
 339
 340         #[test]
 341         #[should_panic]
 342         #[cfg(not(feature = "backtrace"))]
 343         fn recursive_lock_fail() {
 344                 let mutex = Mutex::new(());
 345                 let _a = mutex.lock().unwrap();
 346                 let _b = mutex.lock().unwrap();
 347         }
 348
 349         #[test]
 350         fn recursive_read() {
 351                 let lock = RwLock::new(());
 352                 let _a = lock.read().unwrap();
 353                 let _b = lock.read().unwrap();
 354         }
 355
 356         #[test]
 357         #[should_panic]
 358         fn lockorder_fail() {
 359                 let a = Mutex::new(());
 360                 let b = Mutex::new(());
 361                 {
 362                         let _a = a.lock().unwrap();
 363                         let _b = b.lock().unwrap();
 364                 }
 365                 {
 366                         let _b = b.lock().unwrap();
 367                         let _a = a.lock().unwrap();
 368                 }
 369         }
 370
 371         #[test]
 372         #[should_panic]
 373         fn write_lockorder_fail() {
 374                 let a = RwLock::new(());
 375                 let b = RwLock::new(());
 376                 {
 377                         let _a = a.write().unwrap();
 378                         let _b = b.write().unwrap();
 379                 }
 380                 {
 381                         let _b = b.write().unwrap();
 382                         let _a = a.write().unwrap();
 383                 }
 384         }
 385
 386         #[test]
 387         #[should_panic]
 388         fn read_lockorder_fail() {
 389                 let a = RwLock::new(());
 390                 let b = RwLock::new(());
 391                 {
 392                         let _a = a.read().unwrap();
 393                         let _b = b.read().unwrap();
 394                 }
 395                 {
 396                         let _b = b.read().unwrap();
 397                         let _a = a.read().unwrap();
 398                 }
 399         }
 400
 401         #[test]
 402         fn read_recursive_no_lockorder() {
 403                 // Like the above, but note that no lockorder is implied when we recursively read-lock a
 404                 // RwLock, causing this to pass just fine.
 405                 let a = RwLock::new(());
 406                 let b = RwLock::new(());
 407                 let _outer = a.read().unwrap();
 408                 {
 409                         let _a = a.read().unwrap();
 410                         let _b = b.read().unwrap();
 411                 }
 412                 {
 413                         let _b = b.read().unwrap();
 414                         let _a = a.read().unwrap();
 415                 }
 416         }
 417
 418         #[test]
 419         #[should_panic]
 420         fn read_write_lockorder_fail() {
 421                 let a = RwLock::new(());
 422                 let b = RwLock::new(());
 423                 {
 424                         let _a = a.write().unwrap();
 425                         let _b = b.read().unwrap();
 426                 }
 427                 {
 428                         let _b = b.read().unwrap();
 429                         let _a = a.write().unwrap();
 430                 }
 431         }
 432 }