_ 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 pub use std::sync::WaitTimeoutResult;
  16
  17 use crate::prelude::*;
  18
  19 use super::{LockTestExt, LockHeldState};
  20
  21 #[cfg(feature = "backtrace")]
  22 use {crate::prelude::hash_map, backtrace::Backtrace, std::sync::Once};
  23
  24 #[cfg(not(feature = "backtrace"))]
  25 struct Backtrace{}
  26 #[cfg(not(feature = "backtrace"))]
  27 impl Backtrace { fn new() -> Backtrace { Backtrace {} } }
  28
  29 pub type LockResult<Guard> = Result<Guard, ()>;
  30
  31 pub struct Condvar {
  32         inner: StdCondvar,
  33 }
  34
  35 impl Condvar {
  36         pub fn new() -> Condvar {
  37                 Condvar { inner: StdCondvar::new() }
  38         }
  39
  40         pub fn wait_while<'a, T, F: FnMut(&mut T) -> bool>(&'a self, guard: MutexGuard<'a, T>, condition: F)
  41         -> LockResult<MutexGuard<'a, T>> {
  42                 let mutex: &'a Mutex<T> = guard.mutex;
  43                 self.inner.wait_while(guard.into_inner(), condition).map(|lock| MutexGuard { mutex, lock })
  44                         .map_err(|_| ())
  45         }
  46
  47         #[allow(unused)]
  48         pub fn wait_timeout_while<'a, T, F: FnMut(&mut T) -> bool>(&'a self, guard: MutexGuard<'a, T>, dur: Duration, condition: F)
  49         -> LockResult<(MutexGuard<'a, T>, WaitTimeoutResult)> {
  50                 let mutex = guard.mutex;
  51                 self.inner.wait_timeout_while(guard.into_inner(), dur, condition).map_err(|_| ())
  52                         .map(|(lock, e)| (MutexGuard { mutex, lock }, e))
  53         }
  54
  55         pub fn notify_all(&self) { self.inner.notify_all(); }
  56 }
  57
  58 thread_local! {
  59         /// We track the set of locks currently held by a reference to their `LockMetadata`
  60         static LOCKS_HELD: RefCell<HashMap<u64, Arc<LockMetadata>>> = RefCell::new(new_hash_map());
  61 }
  62 static LOCK_IDX: AtomicUsize = AtomicUsize::new(0);
  63
  64 #[cfg(feature = "backtrace")]
  65 static mut LOCKS: Option<StdMutex<HashMap<String, Arc<LockMetadata>>>> = None;
  66 #[cfg(feature = "backtrace")]
  67 static LOCKS_INIT: Once = Once::new();
  68
  69 /// Metadata about a single lock, by id, the set of things locked-before it, and the backtrace of
  70 /// when the Mutex itself was constructed.
  71 struct LockMetadata {
  72         lock_idx: u64,
  73         locked_before: StdMutex<HashMap<u64, LockDep>>,
  74         _lock_construction_bt: Backtrace,
  75 }
  76
  77 struct LockDep {
  78         lock: Arc<LockMetadata>,
  79         /// lockdep_trace is unused unless we're building with `backtrace`, so we mark it _
  80         _lockdep_trace: Backtrace,
  81 }
  82
  83 // Locates the frame preceding the earliest `debug_sync` frame in the call stack. This ensures we
  84 // can properly detect a lock's construction and acquiral callsites, since the latter may contain
  85 // multiple `debug_sync` frames.
  86 #[cfg(feature = "backtrace")]
  87 fn locate_call_symbol(backtrace: &Backtrace) -> (String, Option<u32>) {
  88         // Find the earliest `debug_sync` frame (or that is in our tests) and use the frame preceding it
  89         // as the callsite. Note that the first few frames may be in the `backtrace` crate, so we have
  90         // to ignore those.
  91         let sync_mutex_constr_regex = regex::Regex::new(r"lightning.*debug_sync").unwrap();
  92         let mut found_debug_sync = false;
  93         let mut symbol_after_latest_debug_sync = None;
  94         for frame in backtrace.frames().iter() {
  95                 for symbol in frame.symbols().iter() {
  96                         if let Some(symbol_name) = symbol.name().map(|name| name.as_str()).flatten() {
  97                                 if !sync_mutex_constr_regex.is_match(symbol_name) {
  98                                         if found_debug_sync {
  99                                                 symbol_after_latest_debug_sync = Some(symbol);
 100                                                 found_debug_sync = false;
 101                                         }
 102                                 } else { found_debug_sync = true; }
 103                         }
 104                 }
 105         }
 106         let symbol = symbol_after_latest_debug_sync.unwrap_or_else(|| {
 107                 panic!("Couldn't find lock call symbol in trace {:?}", backtrace);
 108         });
 109         (format!("{}:{}", symbol.filename().unwrap().display(), symbol.lineno().unwrap()), symbol.colno())
 110 }
 111
 112 impl LockMetadata {
 113         fn new() -> Arc<LockMetadata> {
 114                 let backtrace = Backtrace::new();
 115                 let lock_idx = LOCK_IDX.fetch_add(1, Ordering::Relaxed) as u64;
 116
 117                 let res = Arc::new(LockMetadata {
 118                         locked_before: StdMutex::new(new_hash_map()),
 119                         lock_idx,
 120                         _lock_construction_bt: backtrace,
 121                 });
 122
 123                 #[cfg(feature = "backtrace")]
 124                 {
 125                         let (lock_constr_location, lock_constr_colno) =
 126                                 locate_call_symbol(&res._lock_construction_bt);
 127                         LOCKS_INIT.call_once(|| { unsafe { LOCKS = Some(StdMutex::new(new_hash_map())); } });
 128                         let mut locks = unsafe { LOCKS.as_ref() }.unwrap().lock().unwrap();
 129                         match locks.entry(lock_constr_location) {
 130                                 hash_map::Entry::Occupied(e) => {
 131                                         assert_eq!(lock_constr_colno,
 132                                                 locate_call_symbol(&e.get()._lock_construction_bt).1,
 133                                                 "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.");
 134                                         return Arc::clone(e.get())
 135                                 },
 136                                 hash_map::Entry::Vacant(e) => { e.insert(Arc::clone(&res)); },
 137                         }
 138                 }
 139                 res
 140         }
 141
 142         fn pre_lock(this: &Arc<LockMetadata>, _double_lock_self_allowed: bool) {
 143                 LOCKS_HELD.with(|held| {
 144                         // For each lock that is currently held, check that no lock's `locked_before` set
 145                         // includes the lock we're about to hold, which would imply a lockorder inversion.
 146                         for (locked_idx, _locked) in held.borrow().iter() {
 147                                 if *locked_idx == this.lock_idx {
 148                                         // Note that with `feature = "backtrace"` set, we may be looking at different
 149                                         // instances of the same lock. Still, doing so is quite risky, a total order
 150                                         // must be maintained, and doing so across a set of otherwise-identical mutexes
 151                                         // is fraught with issues.
 152                                         #[cfg(feature = "backtrace")]
 153                                         debug_assert!(_double_lock_self_allowed,
 154                                                 "Tried to acquire a lock while it was held!\nLock constructed at {}",
 155                                                 locate_call_symbol(&this._lock_construction_bt).0);
 156                                         #[cfg(not(feature = "backtrace"))]
 157                                         panic!("Tried to acquire a lock while it was held!");
 158                                 }
 159                         }
 160                         for (_locked_idx, locked) in held.borrow().iter() {
 161                                 for (locked_dep_idx, _locked_dep) in locked.locked_before.lock().unwrap().iter() {
 162                                         let is_dep_this_lock = *locked_dep_idx == this.lock_idx;
 163                                         let has_same_construction = *locked_dep_idx == locked.lock_idx;
 164                                         if is_dep_this_lock && !has_same_construction {
 165                                                 #[allow(unused_mut, unused_assignments)]
 166                                                 let mut has_same_callsite = false;
 167                                                 #[cfg(feature = "backtrace")] {
 168                                                         has_same_callsite = _double_lock_self_allowed &&
 169                                                                 locate_call_symbol(&_locked_dep._lockdep_trace) ==
 170                                                                         locate_call_symbol(&Backtrace::new());
 171                                                 }
 172                                                 if !has_same_callsite {
 173                                                         #[cfg(feature = "backtrace")]
 174                                                         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",
 175                                                                 locate_call_symbol(&this._lock_construction_bt).0,
 176                                                                 this.lock_idx, this._lock_construction_bt,
 177                                                                 locate_call_symbol(&locked._lock_construction_bt).0,
 178                                                                 locked.lock_idx, locked._lock_construction_bt,
 179                                                                 _locked_dep._lockdep_trace);
 180                                                         #[cfg(not(feature = "backtrace"))]
 181                                                         panic!("Tried to violate existing lockorder. Build with the backtrace feature for more info.");
 182                                                 }
 183                                         }
 184                                 }
 185                                 // Insert any already-held locks in our locked-before set.
 186                                 let mut locked_before = this.locked_before.lock().unwrap();
 187                                 if !locked_before.contains_key(&locked.lock_idx) {
 188                                         let lockdep = LockDep { lock: Arc::clone(locked), _lockdep_trace: Backtrace::new() };
 189                                         locked_before.insert(lockdep.lock.lock_idx, lockdep);
 190                                 }
 191                         }
 192                         held.borrow_mut().insert(this.lock_idx, Arc::clone(this));
 193                 });
 194         }
 195
 196         fn held_by_thread(this: &Arc<LockMetadata>) -> LockHeldState {
 197                 let mut res = LockHeldState::NotHeldByThread;
 198                 LOCKS_HELD.with(|held| {
 199                         for (locked_idx, _locked) in held.borrow().iter() {
 200                                 if *locked_idx == this.lock_idx {
 201                                         res = LockHeldState::HeldByThread;
 202                                 }
 203                         }
 204                 });
 205                 res
 206         }
 207
 208         fn try_locked(this: &Arc<LockMetadata>) {
 209                 LOCKS_HELD.with(|held| {
 210                         // Since a try-lock will simply fail if the lock is held already, we do not
 211                         // consider try-locks to ever generate lockorder inversions. However, if a try-lock
 212                         // succeeds, we do consider it to have created lockorder dependencies.
 213                         let mut locked_before = this.locked_before.lock().unwrap();
 214                         for (locked_idx, locked) in held.borrow().iter() {
 215                                 if !locked_before.contains_key(locked_idx) {
 216                                         let lockdep = LockDep { lock: Arc::clone(locked), _lockdep_trace: Backtrace::new() };
 217                                         locked_before.insert(*locked_idx, lockdep);
 218                                 }
 219                         }
 220                         held.borrow_mut().insert(this.lock_idx, Arc::clone(this));
 221                 });
 222         }
 223 }
 224
 225 pub struct Mutex<T: Sized> {
 226         inner: StdMutex<T>,
 227         deps: Arc<LockMetadata>,
 228 }
 229 impl<T: Sized> Mutex<T> {
 230         pub(crate) fn into_inner(self) -> LockResult<T> {
 231                 self.inner.into_inner().map_err(|_| ())
 232         }
 233 }
 234
 235 #[must_use = "if unused the Mutex will immediately unlock"]
 236 pub struct MutexGuard<'a, T: Sized + 'a> {
 237         mutex: &'a Mutex<T>,
 238         lock: StdMutexGuard<'a, T>,
 239 }
 240
 241 impl<'a, T: Sized> MutexGuard<'a, T> {
 242         fn into_inner(self) -> StdMutexGuard<'a, T> {
 243                 // Somewhat unclear why we cannot move out of self.lock, but doing so gets E0509.
 244                 unsafe {
 245                         let v: StdMutexGuard<'a, T> = std::ptr::read(&self.lock);
 246                         std::mem::forget(self);
 247                         v
 248                 }
 249         }
 250 }
 251
 252 impl<T: Sized> Drop for MutexGuard<'_, T> {
 253         fn drop(&mut self) {
 254                 LOCKS_HELD.with(|held| {
 255                         held.borrow_mut().remove(&self.mutex.deps.lock_idx);
 256                 });
 257         }
 258 }
 259
 260 impl<T: Sized> Deref for MutexGuard<'_, T> {
 261         type Target = T;
 262
 263         fn deref(&self) -> &T {
 264                 &self.lock.deref()
 265         }
 266 }
 267
 268 impl<T: Sized> DerefMut for MutexGuard<'_, T> {
 269         fn deref_mut(&mut self) -> &mut T {
 270                 self.lock.deref_mut()
 271         }
 272 }
 273
 274 impl<T> Mutex<T> {
 275         pub fn new(inner: T) -> Mutex<T> {
 276                 Mutex { inner: StdMutex::new(inner), deps: LockMetadata::new() }
 277         }
 278
 279         pub fn lock<'a>(&'a self) -> LockResult<MutexGuard<'a, T>> {
 280                 LockMetadata::pre_lock(&self.deps, false);
 281                 self.inner.lock().map(|lock| MutexGuard { mutex: self, lock }).map_err(|_| ())
 282         }
 283
 284         pub fn try_lock<'a>(&'a self) -> LockResult<MutexGuard<'a, T>> {
 285                 let res = self.inner.try_lock().map(|lock| MutexGuard { mutex: self, lock }).map_err(|_| ());
 286                 if res.is_ok() {
 287                         LockMetadata::try_locked(&self.deps);
 288                 }
 289                 res
 290         }
 291 }
 292
 293 impl<'a, T: 'a> LockTestExt<'a> for Mutex<T> {
 294         #[inline]
 295         fn held_by_thread(&self) -> LockHeldState {
 296                 LockMetadata::held_by_thread(&self.deps)
 297         }
 298         type ExclLock = MutexGuard<'a, T>;
 299         #[inline]
 300         fn unsafe_well_ordered_double_lock_self(&'a self) -> MutexGuard<T> {
 301                 LockMetadata::pre_lock(&self.deps, true);
 302                 self.inner.lock().map(|lock| MutexGuard { mutex: self, lock }).unwrap()
 303         }
 304 }
 305
 306 pub struct RwLock<T: Sized> {
 307         inner: StdRwLock<T>,
 308         deps: Arc<LockMetadata>,
 309 }
 310
 311 pub struct RwLockReadGuard<'a, T: Sized + 'a> {
 312         lock: &'a RwLock<T>,
 313         guard: StdRwLockReadGuard<'a, T>,
 314 }
 315
 316 pub struct RwLockWriteGuard<'a, T: Sized + 'a> {
 317         lock: &'a RwLock<T>,
 318         guard: StdRwLockWriteGuard<'a, T>,
 319 }
 320
 321 impl<T: Sized> Deref for RwLockReadGuard<'_, T> {
 322         type Target = T;
 323
 324         fn deref(&self) -> &T {
 325                 &self.guard.deref()
 326         }
 327 }
 328
 329 impl<T: Sized> Drop for RwLockReadGuard<'_, T> {
 330         fn drop(&mut self) {
 331                 LOCKS_HELD.with(|held| {
 332                         held.borrow_mut().remove(&self.lock.deps.lock_idx);
 333                 });
 334         }
 335 }
 336
 337 impl<T: Sized> Deref for RwLockWriteGuard<'_, T> {
 338         type Target = T;
 339
 340         fn deref(&self) -> &T {
 341                 &self.guard.deref()
 342         }
 343 }
 344
 345 impl<T: Sized> Drop for RwLockWriteGuard<'_, T> {
 346         fn drop(&mut self) {
 347                 LOCKS_HELD.with(|held| {
 348                         held.borrow_mut().remove(&self.lock.deps.lock_idx);
 349                 });
 350         }
 351 }
 352
 353 impl<T: Sized> DerefMut for RwLockWriteGuard<'_, T> {
 354         fn deref_mut(&mut self) -> &mut T {
 355                 self.guard.deref_mut()
 356         }
 357 }
 358
 359 impl<T> RwLock<T> {
 360         pub fn new(inner: T) -> RwLock<T> {
 361                 RwLock { inner: StdRwLock::new(inner), deps: LockMetadata::new() }
 362         }
 363
 364         pub fn read<'a>(&'a self) -> LockResult<RwLockReadGuard<'a, T>> {
 365                 // Note that while we could be taking a recursive read lock here, Rust's `RwLock` may
 366                 // deadlock trying to take a second read lock if another thread is waiting on the write
 367                 // lock. This behavior is platform dependent, but our in-tree `FairRwLock` guarantees
 368                 // such a deadlock.
 369                 LockMetadata::pre_lock(&self.deps, false);
 370                 self.inner.read().map(|guard| RwLockReadGuard { lock: self, guard }).map_err(|_| ())
 371         }
 372
 373         pub fn write<'a>(&'a self) -> LockResult<RwLockWriteGuard<'a, T>> {
 374                 LockMetadata::pre_lock(&self.deps, false);
 375                 self.inner.write().map(|guard| RwLockWriteGuard { lock: self, guard }).map_err(|_| ())
 376         }
 377
 378         pub fn try_write<'a>(&'a self) -> LockResult<RwLockWriteGuard<'a, T>> {
 379                 let res = self.inner.try_write().map(|guard| RwLockWriteGuard { lock: self, guard }).map_err(|_| ());
 380                 if res.is_ok() {
 381                         LockMetadata::try_locked(&self.deps);
 382                 }
 383                 res
 384         }
 385 }
 386
 387 impl<'a, T: 'a> LockTestExt<'a> for RwLock<T> {
 388         #[inline]
 389         fn held_by_thread(&self) -> LockHeldState {
 390                 LockMetadata::held_by_thread(&self.deps)
 391         }
 392         type ExclLock = RwLockWriteGuard<'a, T>;
 393         #[inline]
 394         fn unsafe_well_ordered_double_lock_self(&'a self) -> RwLockWriteGuard<'a, T> {
 395                 LockMetadata::pre_lock(&self.deps, true);
 396                 self.inner.write().map(|guard| RwLockWriteGuard { lock: self, guard }).unwrap()
 397         }
 398 }
 399
 400 pub type FairRwLock<T> = RwLock<T>;