_ 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, Option<u32>) {
  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                                         return (format!("{}:{}", symbol.filename().unwrap().display(), symbol.lineno().unwrap()), symbol.colno());
  90                                 }
  91                         } else { found_debug_sync = true; }
  92                 }
  93         }
  94         panic!("Couldn't find mutex construction callsite");
  95 }
  96
  97 impl LockMetadata {
  98         fn new() -> Arc<LockMetadata> {
  99                 let backtrace = Backtrace::new();
 100                 let lock_idx = LOCK_IDX.fetch_add(1, Ordering::Relaxed) as u64;
 101
 102                 let res = Arc::new(LockMetadata {
 103                         locked_before: StdMutex::new(HashMap::new()),
 104                         lock_idx,
 105                         _lock_construction_bt: backtrace,
 106                 });
 107
 108                 #[cfg(feature = "backtrace")]
 109                 {
 110                         let (lock_constr_location, lock_constr_colno) =
 111                                 get_construction_location(&res._lock_construction_bt);
 112                         LOCKS_INIT.call_once(|| { unsafe { LOCKS = Some(StdMutex::new(HashMap::new())); } });
 113                         let mut locks = unsafe { LOCKS.as_ref() }.unwrap().lock().unwrap();
 114                         match locks.entry(lock_constr_location) {
 115                                 hash_map::Entry::Occupied(e) => {
 116                                         assert_eq!(lock_constr_colno,
 117                                                 get_construction_location(&e.get()._lock_construction_bt).1,
 118                                                 "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.");
 119                                         return Arc::clone(e.get())
 120                                 },
 121                                 hash_map::Entry::Vacant(e) => { e.insert(Arc::clone(&res)); },
 122                         }
 123                 }
 124                 res
 125         }
 126
 127         fn pre_lock(this: &Arc<LockMetadata>, _double_lock_self_allowed: bool) {
 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 *locked_idx == this.lock_idx {
 134                                         // Note that with `feature = "backtrace"` set, we may be looking at different
 135                                         // instances of the same lock. Still, doing so is quite risky, a total order
 136                                         // must be maintained, and doing so across a set of otherwise-identical mutexes
 137                                         // is fraught with issues.
 138                                         #[cfg(feature = "backtrace")]
 139                                         debug_assert!(_double_lock_self_allowed,
 140                                                 "Tried to acquire a lock while it was held!\nLock constructed at {}",
 141                                                 get_construction_location(&this._lock_construction_bt).0);
 142                                         #[cfg(not(feature = "backtrace"))]
 143                                         panic!("Tried to acquire a lock while it was held!");
 144                                 }
 145                         }
 146                         for (_locked_idx, locked) in held.borrow().iter() {
 147                                 for (locked_dep_idx, _locked_dep) in locked.locked_before.lock().unwrap().iter() {
 148                                         if *locked_dep_idx == this.lock_idx && *locked_dep_idx != locked.lock_idx {
 149                                                 #[cfg(feature = "backtrace")]
 150                                                 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",
 151                                                         get_construction_location(&this._lock_construction_bt).0,
 152                                                         this.lock_idx, this._lock_construction_bt,
 153                                                         get_construction_location(&locked._lock_construction_bt).0,
 154                                                         locked.lock_idx, locked._lock_construction_bt,
 155                                                         _locked_dep._lockdep_trace);
 156                                                 #[cfg(not(feature = "backtrace"))]
 157                                                 panic!("Tried to violate existing lockorder. Build with the backtrace feature for more info.");
 158                                         }
 159                                 }
 160                                 // Insert any already-held locks in our locked-before set.
 161                                 let mut locked_before = this.locked_before.lock().unwrap();
 162                                 if !locked_before.contains_key(&locked.lock_idx) {
 163                                         let lockdep = LockDep { lock: Arc::clone(locked), _lockdep_trace: Backtrace::new() };
 164                                         locked_before.insert(lockdep.lock.lock_idx, lockdep);
 165                                 }
 166                         }
 167                         held.borrow_mut().insert(this.lock_idx, Arc::clone(this));
 168                 });
 169         }
 170
 171         fn held_by_thread(this: &Arc<LockMetadata>) -> LockHeldState {
 172                 let mut res = LockHeldState::NotHeldByThread;
 173                 LOCKS_HELD.with(|held| {
 174                         for (locked_idx, _locked) in held.borrow().iter() {
 175                                 if *locked_idx == this.lock_idx {
 176                                         res = LockHeldState::HeldByThread;
 177                                 }
 178                         }
 179                 });
 180                 res
 181         }
 182
 183         fn try_locked(this: &Arc<LockMetadata>) {
 184                 LOCKS_HELD.with(|held| {
 185                         // Since a try-lock will simply fail if the lock is held already, we do not
 186                         // consider try-locks to ever generate lockorder inversions. However, if a try-lock
 187                         // succeeds, we do consider it to have created lockorder dependencies.
 188                         let mut locked_before = this.locked_before.lock().unwrap();
 189                         for (locked_idx, locked) in held.borrow().iter() {
 190                                 if !locked_before.contains_key(locked_idx) {
 191                                         let lockdep = LockDep { lock: Arc::clone(locked), _lockdep_trace: Backtrace::new() };
 192                                         locked_before.insert(*locked_idx, lockdep);
 193                                 }
 194                         }
 195                         held.borrow_mut().insert(this.lock_idx, Arc::clone(this));
 196                 });
 197         }
 198 }
 199
 200 pub struct Mutex<T: Sized> {
 201         inner: StdMutex<T>,
 202         deps: Arc<LockMetadata>,
 203 }
 204
 205 #[must_use = "if unused the Mutex will immediately unlock"]
 206 pub struct MutexGuard<'a, T: Sized + 'a> {
 207         mutex: &'a Mutex<T>,
 208         lock: StdMutexGuard<'a, T>,
 209 }
 210
 211 impl<'a, T: Sized> MutexGuard<'a, T> {
 212         fn into_inner(self) -> StdMutexGuard<'a, T> {
 213                 // Somewhat unclear why we cannot move out of self.lock, but doing so gets E0509.
 214                 unsafe {
 215                         let v: StdMutexGuard<'a, T> = std::ptr::read(&self.lock);
 216                         std::mem::forget(self);
 217                         v
 218                 }
 219         }
 220 }
 221
 222 impl<T: Sized> Drop for MutexGuard<'_, T> {
 223         fn drop(&mut self) {
 224                 LOCKS_HELD.with(|held| {
 225                         held.borrow_mut().remove(&self.mutex.deps.lock_idx);
 226                 });
 227         }
 228 }
 229
 230 impl<T: Sized> Deref for MutexGuard<'_, T> {
 231         type Target = T;
 232
 233         fn deref(&self) -> &T {
 234                 &self.lock.deref()
 235         }
 236 }
 237
 238 impl<T: Sized> DerefMut for MutexGuard<'_, T> {
 239         fn deref_mut(&mut self) -> &mut T {
 240                 self.lock.deref_mut()
 241         }
 242 }
 243
 244 impl<T> Mutex<T> {
 245         pub fn new(inner: T) -> Mutex<T> {
 246                 Mutex { inner: StdMutex::new(inner), deps: LockMetadata::new() }
 247         }
 248
 249         pub fn lock<'a>(&'a self) -> LockResult<MutexGuard<'a, T>> {
 250                 LockMetadata::pre_lock(&self.deps, false);
 251                 self.inner.lock().map(|lock| MutexGuard { mutex: self, lock }).map_err(|_| ())
 252         }
 253
 254         pub fn try_lock<'a>(&'a self) -> LockResult<MutexGuard<'a, T>> {
 255                 let res = self.inner.try_lock().map(|lock| MutexGuard { mutex: self, lock }).map_err(|_| ());
 256                 if res.is_ok() {
 257                         LockMetadata::try_locked(&self.deps);
 258                 }
 259                 res
 260         }
 261 }
 262
 263 impl<'a, T: 'a> LockTestExt<'a> for Mutex<T> {
 264         #[inline]
 265         fn held_by_thread(&self) -> LockHeldState {
 266                 LockMetadata::held_by_thread(&self.deps)
 267         }
 268         type ExclLock = MutexGuard<'a, T>;
 269         #[inline]
 270         fn unsafe_well_ordered_double_lock_self(&'a self) -> MutexGuard<T> {
 271                 LockMetadata::pre_lock(&self.deps, true);
 272                 self.inner.lock().map(|lock| MutexGuard { mutex: self, lock }).unwrap()
 273         }
 274 }
 275
 276 pub struct RwLock<T: Sized> {
 277         inner: StdRwLock<T>,
 278         deps: Arc<LockMetadata>,
 279 }
 280
 281 pub struct RwLockReadGuard<'a, T: Sized + 'a> {
 282         lock: &'a RwLock<T>,
 283         guard: StdRwLockReadGuard<'a, T>,
 284 }
 285
 286 pub struct RwLockWriteGuard<'a, T: Sized + 'a> {
 287         lock: &'a RwLock<T>,
 288         guard: StdRwLockWriteGuard<'a, T>,
 289 }
 290
 291 impl<T: Sized> Deref for RwLockReadGuard<'_, T> {
 292         type Target = T;
 293
 294         fn deref(&self) -> &T {
 295                 &self.guard.deref()
 296         }
 297 }
 298
 299 impl<T: Sized> Drop for RwLockReadGuard<'_, 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> Deref for RwLockWriteGuard<'_, T> {
 308         type Target = T;
 309
 310         fn deref(&self) -> &T {
 311                 &self.guard.deref()
 312         }
 313 }
 314
 315 impl<T: Sized> Drop for RwLockWriteGuard<'_, T> {
 316         fn drop(&mut self) {
 317                 LOCKS_HELD.with(|held| {
 318                         held.borrow_mut().remove(&self.lock.deps.lock_idx);
 319                 });
 320         }
 321 }
 322
 323 impl<T: Sized> DerefMut for RwLockWriteGuard<'_, T> {
 324         fn deref_mut(&mut self) -> &mut T {
 325                 self.guard.deref_mut()
 326         }
 327 }
 328
 329 impl<T> RwLock<T> {
 330         pub fn new(inner: T) -> RwLock<T> {
 331                 RwLock { inner: StdRwLock::new(inner), deps: LockMetadata::new() }
 332         }
 333
 334         pub fn read<'a>(&'a self) -> LockResult<RwLockReadGuard<'a, T>> {
 335                 // Note that while we could be taking a recursive read lock here, Rust's `RwLock` may
 336                 // deadlock trying to take a second read lock if another thread is waiting on the write
 337                 // lock. This behavior is platform dependent, but our in-tree `FairRwLock` guarantees
 338                 // such a deadlock.
 339                 LockMetadata::pre_lock(&self.deps, false);
 340                 self.inner.read().map(|guard| RwLockReadGuard { lock: self, guard }).map_err(|_| ())
 341         }
 342
 343         pub fn write<'a>(&'a self) -> LockResult<RwLockWriteGuard<'a, T>> {
 344                 LockMetadata::pre_lock(&self.deps, false);
 345                 self.inner.write().map(|guard| RwLockWriteGuard { lock: self, guard }).map_err(|_| ())
 346         }
 347
 348         pub fn try_write<'a>(&'a self) -> LockResult<RwLockWriteGuard<'a, T>> {
 349                 let res = self.inner.try_write().map(|guard| RwLockWriteGuard { lock: self, guard }).map_err(|_| ());
 350                 if res.is_ok() {
 351                         LockMetadata::try_locked(&self.deps);
 352                 }
 353                 res
 354         }
 355 }
 356
 357 impl<'a, T: 'a> LockTestExt<'a> for RwLock<T> {
 358         #[inline]
 359         fn held_by_thread(&self) -> LockHeldState {
 360                 LockMetadata::held_by_thread(&self.deps)
 361         }
 362         type ExclLock = RwLockWriteGuard<'a, T>;
 363         #[inline]
 364         fn unsafe_well_ordered_double_lock_self(&'a self) -> RwLockWriteGuard<'a, T> {
 365                 LockMetadata::pre_lock(&self.deps, true);
 366                 self.inner.write().map(|guard| RwLockWriteGuard { lock: self, guard }).unwrap()
 367         }
 368 }
 369
 370 pub type FairRwLock<T> = RwLock<T>;