git.bitcoin.ninja 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 crate::prelude::HashMap;
  16
  17 #[cfg(feature = "backtrace")]
  18 use {crate::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                                         let res = if let Some(col) = symbol.colno() {
  88                                                 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                                                 format!("{}:{}", symbol.filename().unwrap().display(), symbol.lineno().unwrap())
  93                                         };
  94 eprintln!("{}: {}", res, symbol_name);
  95 return res;
  96                                 }
  97                         } else { found_debug_sync = true; }
  98                 }
  99         }
 100         panic!("Couldn't find mutex construction callsite");
 101 }
 102
 103 impl LockMetadata {
 104         fn new() -> Arc<LockMetadata> {
 105                 let backtrace = Backtrace::new();
 106                 let lock_idx = LOCK_IDX.fetch_add(1, Ordering::Relaxed) as u64;
 107
 108                 let res = Arc::new(LockMetadata {
 109                         locked_before: StdMutex::new(HashMap::new()),
 110                         lock_idx,
 111                         _lock_construction_bt: backtrace,
 112                 });
 113
 114                 #[cfg(feature = "backtrace")]
 115                 {
 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)); },
 122                         }
 123                 }
 124                 res
 125         }
 126
 127         // Returns whether we were a recursive lock (only relevant for read)
 128         fn _pre_lock(this: &Arc<LockMetadata>, read: bool) -> bool {
 129                 let mut inserted = false;
 130                 LOCKS_HELD.with(|held| {
 131                         // For each lock which is currently locked, check that no lock's locked-before
 132                         // set includes the lock we're about to lock, which would imply a lockorder
 133                         // inversion.
 134                         for (locked_idx, _locked) in held.borrow().iter() {
 135                                 if read && *locked_idx == this.lock_idx {
 136                                         // Recursive read locks are explicitly allowed
 137                                         return;
 138                                 }
 139                         }
 140                         for (locked_idx, locked) in held.borrow().iter() {
 141                                 if !read && *locked_idx == this.lock_idx {
 142                                         // With `feature = "backtrace"` set, we may be looking at different instances
 143                                         // of the same lock.
 144                                         debug_assert!(cfg!(feature = "backtrace"), "Tried to acquire a lock while it was held!");
 145                                 }
 146                                 for (locked_dep_idx, _locked_dep) in locked.locked_before.lock().unwrap().iter() {
 147                                         if *locked_dep_idx == this.lock_idx && *locked_dep_idx != locked.lock_idx {
 148                                                 #[cfg(feature = "backtrace")]
 149                                                 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",
 150                                                         get_construction_location(&this._lock_construction_bt), this.lock_idx, this._lock_construction_bt,
 151                                                         get_construction_location(&locked._lock_construction_bt), locked.lock_idx, locked._lock_construction_bt,
 152                                                         _locked_dep._lockdep_trace);
 153                                                 #[cfg(not(feature = "backtrace"))]
 154                                                 panic!("Tried to violate existing lockorder. Build with the backtrace feature for more info.");
 155                                         }
 156                                 }
 157                                 // Insert any already-held locks in our locked-before set.
 158                                 let mut locked_before = this.locked_before.lock().unwrap();
 159                                 if !locked_before.contains_key(&locked.lock_idx) {
 160                                         let lockdep = LockDep { lock: Arc::clone(locked), _lockdep_trace: Backtrace::new() };
 161                                         locked_before.insert(lockdep.lock.lock_idx, lockdep);
 162                                 }
 163                         }
 164                         held.borrow_mut().insert(this.lock_idx, Arc::clone(this));
 165                         inserted = true;
 166                 });
 167                 inserted
 168         }
 169
 170         fn pre_lock(this: &Arc<LockMetadata>) { Self::_pre_lock(this, false); }
 171         fn pre_read_lock(this: &Arc<LockMetadata>) -> bool { Self::_pre_lock(this, true) }
 172
 173         fn try_locked(this: &Arc<LockMetadata>) {
 174                 LOCKS_HELD.with(|held| {
 175                         // Since a try-lock will simply fail if the lock is held already, we do not
 176                         // consider try-locks to ever generate lockorder inversions. However, if a try-lock
 177                         // succeeds, we do consider it to have created lockorder dependencies.
 178                         let mut locked_before = this.locked_before.lock().unwrap();
 179                         for (locked_idx, locked) in held.borrow().iter() {
 180                                 if !locked_before.contains_key(locked_idx) {
 181                                         let lockdep = LockDep { lock: Arc::clone(locked), _lockdep_trace: Backtrace::new() };
 182                                         locked_before.insert(*locked_idx, lockdep);
 183                                 }
 184                         }
 185                         held.borrow_mut().insert(this.lock_idx, Arc::clone(this));
 186                 });
 187         }
 188 }
 189
 190 pub struct Mutex<T: Sized> {
 191         inner: StdMutex<T>,
 192         deps: Arc<LockMetadata>,
 193 }
 194
 195 #[must_use = "if unused the Mutex will immediately unlock"]
 196 pub struct MutexGuard<'a, T: Sized + 'a> {
 197         mutex: &'a Mutex<T>,
 198         lock: StdMutexGuard<'a, T>,
 199 }
 200
 201 impl<'a, T: Sized> MutexGuard<'a, T> {
 202         fn into_inner(self) -> StdMutexGuard<'a, T> {
 203                 // Somewhat unclear why we cannot move out of self.lock, but doing so gets E0509.
 204                 unsafe {
 205                         let v: StdMutexGuard<'a, T> = std::ptr::read(&self.lock);
 206                         std::mem::forget(self);
 207                         v
 208                 }
 209         }
 210 }
 211
 212 impl<T: Sized> Drop for MutexGuard<'_, T> {
 213         fn drop(&mut self) {
 214                 LOCKS_HELD.with(|held| {
 215                         held.borrow_mut().remove(&self.mutex.deps.lock_idx);
 216                 });
 217         }
 218 }
 219
 220 impl<T: Sized> Deref for MutexGuard<'_, T> {
 221         type Target = T;
 222
 223         fn deref(&self) -> &T {
 224                 &self.lock.deref()
 225         }
 226 }
 227
 228 impl<T: Sized> DerefMut for MutexGuard<'_, T> {
 229         fn deref_mut(&mut self) -> &mut T {
 230                 self.lock.deref_mut()
 231         }
 232 }
 233
 234 impl<T> Mutex<T> {
 235         pub fn new(inner: T) -> Mutex<T> {
 236                 Mutex { inner: StdMutex::new(inner), deps: LockMetadata::new() }
 237         }
 238
 239         pub fn lock<'a>(&'a self) -> LockResult<MutexGuard<'a, T>> {
 240                 LockMetadata::pre_lock(&self.deps);
 241                 self.inner.lock().map(|lock| MutexGuard { mutex: self, lock }).map_err(|_| ())
 242         }
 243
 244         pub fn try_lock<'a>(&'a self) -> LockResult<MutexGuard<'a, T>> {
 245                 let res = self.inner.try_lock().map(|lock| MutexGuard { mutex: self, lock }).map_err(|_| ());
 246                 if res.is_ok() {
 247                         LockMetadata::try_locked(&self.deps);
 248                 }
 249                 res
 250         }
 251 }
 252
 253 pub struct RwLock<T: Sized> {
 254         inner: StdRwLock<T>,
 255         deps: Arc<LockMetadata>,
 256 }
 257
 258 pub struct RwLockReadGuard<'a, T: Sized + 'a> {
 259         lock: &'a RwLock<T>,
 260         first_lock: bool,
 261         guard: StdRwLockReadGuard<'a, T>,
 262 }
 263
 264 pub struct RwLockWriteGuard<'a, T: Sized + 'a> {
 265         lock: &'a RwLock<T>,
 266         guard: StdRwLockWriteGuard<'a, T>,
 267 }
 268
 269 impl<T: Sized> Deref for RwLockReadGuard<'_, T> {
 270         type Target = T;
 271
 272         fn deref(&self) -> &T {
 273                 &self.guard.deref()
 274         }
 275 }
 276
 277 impl<T: Sized> Drop for RwLockReadGuard<'_, T> {
 278         fn drop(&mut self) {
 279                 if !self.first_lock {
 280                         // Note that its not strictly true that the first taken read lock will get unlocked
 281                         // last, but in practice our locks are always taken as RAII, so it should basically
 282                         // always be true.
 283                         return;
 284                 }
 285                 LOCKS_HELD.with(|held| {
 286                         held.borrow_mut().remove(&self.lock.deps.lock_idx);
 287                 });
 288         }
 289 }
 290
 291 impl<T: Sized> Deref for RwLockWriteGuard<'_, T> {
 292         type Target = T;
 293
 294         fn deref(&self) -> &T {
 295                 &self.guard.deref()
 296         }
 297 }
 298
 299 impl<T: Sized> Drop for RwLockWriteGuard<'_, T> {
 300         fn drop(&mut self) {
 301                 LOCKS_HELD.with(|held| {
 302                         held.borrow_mut().remove(&self.lock.deps.lock_idx);
 303                 });
 304         }
 305 }
 306
 307 impl<T: Sized> DerefMut for RwLockWriteGuard<'_, T> {
 308         fn deref_mut(&mut self) -> &mut T {
 309                 self.guard.deref_mut()
 310         }
 311 }
 312
 313 impl<T> RwLock<T> {
 314         pub fn new(inner: T) -> RwLock<T> {
 315                 RwLock { inner: StdRwLock::new(inner), deps: LockMetadata::new() }
 316         }
 317
 318         pub fn read<'a>(&'a self) -> LockResult<RwLockReadGuard<'a, T>> {
 319                 let first_lock = LockMetadata::pre_read_lock(&self.deps);
 320                 self.inner.read().map(|guard| RwLockReadGuard { lock: self, guard, first_lock }).map_err(|_| ())
 321         }
 322
 323         pub fn write<'a>(&'a self) -> LockResult<RwLockWriteGuard<'a, T>> {
 324                 LockMetadata::pre_lock(&self.deps);
 325                 self.inner.write().map(|guard| RwLockWriteGuard { lock: self, guard }).map_err(|_| ())
 326         }
 327
 328         pub fn try_write<'a>(&'a self) -> LockResult<RwLockWriteGuard<'a, T>> {
 329                 let res = self.inner.try_write().map(|guard| RwLockWriteGuard { lock: self, guard }).map_err(|_| ());
 330                 if res.is_ok() {
 331                         LockMetadata::try_locked(&self.deps);
 332                 }
 333                 res
 334         }
 335 }
 336
 337 pub type FairRwLock<T> = RwLock<T>;
 338
 339 mod tests {
 340         use super::{RwLock, Mutex};
 341
 342         #[test]
 343         #[should_panic]
 344         #[cfg(not(feature = "backtrace"))]
 345         fn recursive_lock_fail() {
 346                 let mutex = Mutex::new(());
 347                 let _a = mutex.lock().unwrap();
 348                 let _b = mutex.lock().unwrap();
 349         }
 350
 351         #[test]
 352         fn recursive_read() {
 353                 let lock = RwLock::new(());
 354                 let _a = lock.read().unwrap();
 355                 let _b = lock.read().unwrap();
 356         }
 357
 358         #[test]
 359         #[should_panic]
 360         fn lockorder_fail() {
 361                 let a = Mutex::new(());
 362                 let b = Mutex::new(());
 363                 {
 364                         let _a = a.lock().unwrap();
 365                         let _b = b.lock().unwrap();
 366                 }
 367                 {
 368                         let _b = b.lock().unwrap();
 369                         let _a = a.lock().unwrap();
 370                 }
 371         }
 372
 373         #[test]
 374         #[should_panic]
 375         fn write_lockorder_fail() {
 376                 let a = RwLock::new(());
 377                 let b = RwLock::new(());
 378                 {
 379                         let _a = a.write().unwrap();
 380                         let _b = b.write().unwrap();
 381                 }
 382                 {
 383                         let _b = b.write().unwrap();
 384                         let _a = a.write().unwrap();
 385                 }
 386         }
 387
 388         #[test]
 389         #[should_panic]
 390         fn read_lockorder_fail() {
 391                 let a = RwLock::new(());
 392                 let b = RwLock::new(());
 393                 {
 394                         let _a = a.read().unwrap();
 395                         let _b = b.read().unwrap();
 396                 }
 397                 {
 398                         let _b = b.read().unwrap();
 399                         let _a = a.read().unwrap();
 400                 }
 401         }
 402
 403         #[test]
 404         fn read_recursive_no_lockorder() {
 405                 // Like the above, but note that no lockorder is implied when we recursively read-lock a
 406                 // RwLock, causing this to pass just fine.
 407                 let a = RwLock::new(());
 408                 let b = RwLock::new(());
 409                 let _outer = a.read().unwrap();
 410                 {
 411                         let _a = a.read().unwrap();
 412                         let _b = b.read().unwrap();
 413                 }
 414                 {
 415                         let _b = b.read().unwrap();
 416                         let _a = a.read().unwrap();
 417                 }
 418         }
 419
 420         #[test]
 421         #[should_panic]
 422         fn read_write_lockorder_fail() {
 423                 let a = RwLock::new(());
 424                 let b = RwLock::new(());
 425                 {
 426                         let _a = a.write().unwrap();
 427                         let _b = b.read().unwrap();
 428                 }
 429                 {
 430                         let _b = b.read().unwrap();
 431                         let _a = a.write().unwrap();
 432                 }
 433         }
 434 }