_ 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 use crate::prelude::HashMap;
  16
  17 use super::{LockTestExt, LockHeldState};
  18
  19 #[cfg(feature = "backtrace")]
  20 use {crate::prelude::hash_map, backtrace::Backtrace, std::sync::Once};
  21
  22 #[cfg(not(feature = "backtrace"))]
  23 struct Backtrace{}
  24 #[cfg(not(feature = "backtrace"))]
  25 impl Backtrace { fn new() -> Backtrace { Backtrace {} } }
  26
  27 pub type LockResult<Guard> = Result<Guard, ()>;
  28
  29 pub struct Condvar {
  30         inner: StdCondvar,
  31 }
  32
  33 impl Condvar {
  34         pub fn new() -> Condvar {
  35                 Condvar { inner: StdCondvar::new() }
  36         }
  37
  38         pub fn wait<'a, T>(&'a self, guard: MutexGuard<'a, T>) -> LockResult<MutexGuard<'a, T>> {
  39                 let mutex: &'a Mutex<T> = guard.mutex;
  40                 self.inner.wait(guard.into_inner()).map(|lock| MutexGuard { mutex, lock }).map_err(|_| ())
  41         }
  42
  43         #[allow(unused)]
  44         pub fn wait_timeout<'a, T>(&'a self, guard: MutexGuard<'a, T>, dur: Duration) -> LockResult<(MutexGuard<'a, T>, ())> {
  45                 let mutex = guard.mutex;
  46                 self.inner.wait_timeout(guard.into_inner(), dur).map(|(lock, _)| (MutexGuard { mutex, lock }, ())).map_err(|_| ())
  47         }
  48
  49         pub fn notify_all(&self) { self.inner.notify_all(); }
  50 }
  51
  52 thread_local! {
  53         /// We track the set of locks currently held by a reference to their `LockMetadata`
  54         static LOCKS_HELD: RefCell<HashMap<u64, Arc<LockMetadata>>> = RefCell::new(HashMap::new());
  55 }
  56 static LOCK_IDX: AtomicUsize = AtomicUsize::new(0);
  57
  58 #[cfg(feature = "backtrace")]
  59 static mut LOCKS: Option<StdMutex<HashMap<String, Arc<LockMetadata>>>> = None;
  60 #[cfg(feature = "backtrace")]
  61 static LOCKS_INIT: Once = Once::new();
  62
  63 /// Metadata about a single lock, by id, the set of things locked-before it, and the backtrace of
  64 /// when the Mutex itself was constructed.
  65 struct LockMetadata {
  66         lock_idx: u64,
  67         locked_before: StdMutex<HashMap<u64, LockDep>>,
  68         _lock_construction_bt: Backtrace,
  69 }
  70
  71 struct LockDep {
  72         lock: Arc<LockMetadata>,
  73         /// lockdep_trace is unused unless we're building with `backtrace`, so we mark it _
  74         _lockdep_trace: Backtrace,
  75 }
  76
  77 #[cfg(feature = "backtrace")]
  78 fn get_construction_location(backtrace: &Backtrace) -> String {
  79         // Find the first frame that is after `debug_sync` (or that is in our tests) and use
  80         // that as the mutex construction site. Note that the first few frames may be in
  81         // the `backtrace` crate, so we have to ignore those.
  82         let sync_mutex_constr_regex = regex::Regex::new(r"lightning.*debug_sync").unwrap();
  83         let mut found_debug_sync = false;
  84         for frame in backtrace.frames() {
  85                 for symbol in frame.symbols() {
  86                         let symbol_name = symbol.name().unwrap().as_str().unwrap();
  87                         if !sync_mutex_constr_regex.is_match(symbol_name) {
  88                                 if found_debug_sync {
  89                                         if let Some(col) = symbol.colno() {
  90                                                 return format!("{}:{}:{}", symbol.filename().unwrap().display(), symbol.lineno().unwrap(), col);
  91                                         } else {
  92                                                 // Windows debug symbols don't support column numbers, so fall back to
  93                                                 // line numbers only if no `colno` is available
  94                                                 return format!("{}:{}", symbol.filename().unwrap().display(), symbol.lineno().unwrap());
  95                                         }
  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 held_by_thread(this: &Arc<LockMetadata>) -> LockHeldState {
 174                 let mut res = LockHeldState::NotHeldByThread;
 175                 LOCKS_HELD.with(|held| {
 176                         for (locked_idx, _locked) in held.borrow().iter() {
 177                                 if *locked_idx == this.lock_idx {
 178                                         res = LockHeldState::HeldByThread;
 179                                 }
 180                         }
 181                 });
 182                 res
 183         }
 184
 185         fn try_locked(this: &Arc<LockMetadata>) {
 186                 LOCKS_HELD.with(|held| {
 187                         // Since a try-lock will simply fail if the lock is held already, we do not
 188                         // consider try-locks to ever generate lockorder inversions. However, if a try-lock
 189                         // succeeds, we do consider it to have created lockorder dependencies.
 190                         let mut locked_before = this.locked_before.lock().unwrap();
 191                         for (locked_idx, locked) in held.borrow().iter() {
 192                                 if !locked_before.contains_key(locked_idx) {
 193                                         let lockdep = LockDep { lock: Arc::clone(locked), _lockdep_trace: Backtrace::new() };
 194                                         locked_before.insert(*locked_idx, lockdep);
 195                                 }
 196                         }
 197                         held.borrow_mut().insert(this.lock_idx, Arc::clone(this));
 198                 });
 199         }
 200 }
 201
 202 pub struct Mutex<T: Sized> {
 203         inner: StdMutex<T>,
 204         deps: Arc<LockMetadata>,
 205 }
 206
 207 #[must_use = "if unused the Mutex will immediately unlock"]
 208 pub struct MutexGuard<'a, T: Sized + 'a> {
 209         mutex: &'a Mutex<T>,
 210         lock: StdMutexGuard<'a, T>,
 211 }
 212
 213 impl<'a, T: Sized> MutexGuard<'a, T> {
 214         fn into_inner(self) -> StdMutexGuard<'a, T> {
 215                 // Somewhat unclear why we cannot move out of self.lock, but doing so gets E0509.
 216                 unsafe {
 217                         let v: StdMutexGuard<'a, T> = std::ptr::read(&self.lock);
 218                         std::mem::forget(self);
 219                         v
 220                 }
 221         }
 222 }
 223
 224 impl<T: Sized> Drop for MutexGuard<'_, T> {
 225         fn drop(&mut self) {
 226                 LOCKS_HELD.with(|held| {
 227                         held.borrow_mut().remove(&self.mutex.deps.lock_idx);
 228                 });
 229         }
 230 }
 231
 232 impl<T: Sized> Deref for MutexGuard<'_, T> {
 233         type Target = T;
 234
 235         fn deref(&self) -> &T {
 236                 &self.lock.deref()
 237         }
 238 }
 239
 240 impl<T: Sized> DerefMut for MutexGuard<'_, T> {
 241         fn deref_mut(&mut self) -> &mut T {
 242                 self.lock.deref_mut()
 243         }
 244 }
 245
 246 impl<T> Mutex<T> {
 247         pub fn new(inner: T) -> Mutex<T> {
 248                 Mutex { inner: StdMutex::new(inner), deps: LockMetadata::new() }
 249         }
 250
 251         pub fn lock<'a>(&'a self) -> LockResult<MutexGuard<'a, T>> {
 252                 LockMetadata::pre_lock(&self.deps);
 253                 self.inner.lock().map(|lock| MutexGuard { mutex: self, lock }).map_err(|_| ())
 254         }
 255
 256         pub fn try_lock<'a>(&'a self) -> LockResult<MutexGuard<'a, T>> {
 257                 let res = self.inner.try_lock().map(|lock| MutexGuard { mutex: self, lock }).map_err(|_| ());
 258                 if res.is_ok() {
 259                         LockMetadata::try_locked(&self.deps);
 260                 }
 261                 res
 262         }
 263 }
 264
 265 impl <T> LockTestExt for Mutex<T> {
 266         #[inline]
 267         fn held_by_thread(&self) -> LockHeldState {
 268                 LockMetadata::held_by_thread(&self.deps)
 269         }
 270 }
 271
 272 pub struct RwLock<T: Sized> {
 273         inner: StdRwLock<T>,
 274         deps: Arc<LockMetadata>,
 275 }
 276
 277 pub struct RwLockReadGuard<'a, T: Sized + 'a> {
 278         lock: &'a RwLock<T>,
 279         first_lock: bool,
 280         guard: StdRwLockReadGuard<'a, T>,
 281 }
 282
 283 pub struct RwLockWriteGuard<'a, T: Sized + 'a> {
 284         lock: &'a RwLock<T>,
 285         guard: StdRwLockWriteGuard<'a, T>,
 286 }
 287
 288 impl<T: Sized> Deref for RwLockReadGuard<'_, T> {
 289         type Target = T;
 290
 291         fn deref(&self) -> &T {
 292                 &self.guard.deref()
 293         }
 294 }
 295
 296 impl<T: Sized> Drop for RwLockReadGuard<'_, T> {
 297         fn drop(&mut self) {
 298                 if !self.first_lock {
 299                         // Note that its not strictly true that the first taken read lock will get unlocked
 300                         // last, but in practice our locks are always taken as RAII, so it should basically
 301                         // always be true.
 302                         return;
 303                 }
 304                 LOCKS_HELD.with(|held| {
 305                         held.borrow_mut().remove(&self.lock.deps.lock_idx);
 306                 });
 307         }
 308 }
 309
 310 impl<T: Sized> Deref for RwLockWriteGuard<'_, T> {
 311         type Target = T;
 312
 313         fn deref(&self) -> &T {
 314                 &self.guard.deref()
 315         }
 316 }
 317
 318 impl<T: Sized> Drop for RwLockWriteGuard<'_, T> {
 319         fn drop(&mut self) {
 320                 LOCKS_HELD.with(|held| {
 321                         held.borrow_mut().remove(&self.lock.deps.lock_idx);
 322                 });
 323         }
 324 }
 325
 326 impl<T: Sized> DerefMut for RwLockWriteGuard<'_, T> {
 327         fn deref_mut(&mut self) -> &mut T {
 328                 self.guard.deref_mut()
 329         }
 330 }
 331
 332 impl<T> RwLock<T> {
 333         pub fn new(inner: T) -> RwLock<T> {
 334                 RwLock { inner: StdRwLock::new(inner), deps: LockMetadata::new() }
 335         }
 336
 337         pub fn read<'a>(&'a self) -> LockResult<RwLockReadGuard<'a, T>> {
 338                 let first_lock = LockMetadata::pre_read_lock(&self.deps);
 339                 self.inner.read().map(|guard| RwLockReadGuard { lock: self, guard, first_lock }).map_err(|_| ())
 340         }
 341
 342         pub fn write<'a>(&'a self) -> LockResult<RwLockWriteGuard<'a, T>> {
 343                 LockMetadata::pre_lock(&self.deps);
 344                 self.inner.write().map(|guard| RwLockWriteGuard { lock: self, guard }).map_err(|_| ())
 345         }
 346
 347         pub fn try_write<'a>(&'a self) -> LockResult<RwLockWriteGuard<'a, T>> {
 348                 let res = self.inner.try_write().map(|guard| RwLockWriteGuard { lock: self, guard }).map_err(|_| ());
 349                 if res.is_ok() {
 350                         LockMetadata::try_locked(&self.deps);
 351                 }
 352                 res
 353         }
 354 }
 355
 356 impl <T> LockTestExt for RwLock<T> {
 357         #[inline]
 358         fn held_by_thread(&self) -> LockHeldState {
 359                 LockMetadata::held_by_thread(&self.deps)
 360         }
 361 }
 362
 363 pub type FairRwLock<T> = RwLock<T>;