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