}
#[cfg(feature = "backtrace")]
-fn get_construction_location(backtrace: &Backtrace) -> String {
+fn get_construction_location(backtrace: &Backtrace) -> (String, Option<u32>) {
// Find the first frame that is after `debug_sync` (or that is in our tests) and use
// that as the mutex construction site. Note that the first few frames may be in
// the `backtrace` crate, so we have to ignore those.
let symbol_name = symbol.name().unwrap().as_str().unwrap();
if !sync_mutex_constr_regex.is_match(symbol_name) {
if found_debug_sync {
- if let Some(col) = symbol.colno() {
- return format!("{}:{}:{}", symbol.filename().unwrap().display(), symbol.lineno().unwrap(), col);
- } else {
- // Windows debug symbols don't support column numbers, so fall back to
- // line numbers only if no `colno` is available
- return format!("{}:{}", symbol.filename().unwrap().display(), symbol.lineno().unwrap());
- }
+ return (format!("{}:{}", symbol.filename().unwrap().display(), symbol.lineno().unwrap()), symbol.colno());
}
} else { found_debug_sync = true; }
}
#[cfg(feature = "backtrace")]
{
- let lock_constr_location = get_construction_location(&res._lock_construction_bt);
+ let (lock_constr_location, lock_constr_colno) =
+ get_construction_location(&res._lock_construction_bt);
LOCKS_INIT.call_once(|| { unsafe { LOCKS = Some(StdMutex::new(HashMap::new())); } });
let mut locks = unsafe { LOCKS.as_ref() }.unwrap().lock().unwrap();
match locks.entry(lock_constr_location) {
- hash_map::Entry::Occupied(e) => return Arc::clone(e.get()),
+ hash_map::Entry::Occupied(e) => {
+ assert_eq!(lock_constr_colno,
+ get_construction_location(&e.get()._lock_construction_bt).1,
+ "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.");
+ return Arc::clone(e.get())
+ },
hash_map::Entry::Vacant(e) => { e.insert(Arc::clone(&res)); },
}
}
res
}
- // Returns whether we were a recursive lock (only relevant for read)
- fn _pre_lock(this: &Arc<LockMetadata>, read: bool) -> bool {
- let mut inserted = false;
+ fn pre_lock(this: &Arc<LockMetadata>, _double_lock_self_allowed: bool) {
LOCKS_HELD.with(|held| {
// For each lock which is currently locked, check that no lock's locked-before
// set includes the lock we're about to lock, which would imply a lockorder
// inversion.
- for (locked_idx, _locked) in held.borrow().iter() {
- if read && *locked_idx == this.lock_idx {
- // Recursive read locks are explicitly allowed
- return;
+ for (locked_idx, locked) in held.borrow().iter() {
+ if *locked_idx == this.lock_idx {
+ // Note that with `feature = "backtrace"` set, we may be looking at different
+ // instances of the same lock. Still, doing so is quite risky, a total order
+ // must be maintained, and doing so across a set of otherwise-identical mutexes
+ // is fraught with issues.
+ #[cfg(feature = "backtrace")]
+ debug_assert!(_double_lock_self_allowed,
+ "Tried to acquire a lock while it was held!\nLock constructed at {}",
+ get_construction_location(&this._lock_construction_bt).0);
+ #[cfg(not(feature = "backtrace"))]
+ panic!("Tried to acquire a lock while it was held!");
}
}
for (locked_idx, locked) in held.borrow().iter() {
- if !read && *locked_idx == this.lock_idx {
- // With `feature = "backtrace"` set, we may be looking at different instances
- // of the same lock.
- debug_assert!(cfg!(feature = "backtrace"), "Tried to acquire a lock while it was held!");
- }
for (locked_dep_idx, _locked_dep) in locked.locked_before.lock().unwrap().iter() {
if *locked_dep_idx == this.lock_idx && *locked_dep_idx != locked.lock_idx {
#[cfg(feature = "backtrace")]
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",
- get_construction_location(&this._lock_construction_bt), this.lock_idx, this._lock_construction_bt,
- get_construction_location(&locked._lock_construction_bt), locked.lock_idx, locked._lock_construction_bt,
+ get_construction_location(&this._lock_construction_bt).0,
+ this.lock_idx, this._lock_construction_bt,
+ get_construction_location(&locked._lock_construction_bt).0,
+ locked.lock_idx, locked._lock_construction_bt,
_locked_dep._lockdep_trace);
#[cfg(not(feature = "backtrace"))]
panic!("Tried to violate existing lockorder. Build with the backtrace feature for more info.");
}
}
held.borrow_mut().insert(this.lock_idx, Arc::clone(this));
- inserted = true;
});
- inserted
}
- fn pre_lock(this: &Arc<LockMetadata>) { Self::_pre_lock(this, false); }
- fn pre_read_lock(this: &Arc<LockMetadata>) -> bool { Self::_pre_lock(this, true) }
-
fn held_by_thread(this: &Arc<LockMetadata>) -> LockHeldState {
let mut res = LockHeldState::NotHeldByThread;
LOCKS_HELD.with(|held| {
}
pub fn lock<'a>(&'a self) -> LockResult<MutexGuard<'a, T>> {
- LockMetadata::pre_lock(&self.deps);
+ LockMetadata::pre_lock(&self.deps, false);
self.inner.lock().map(|lock| MutexGuard { mutex: self, lock }).map_err(|_| ())
}
}
}
-impl <T> LockTestExt for Mutex<T> {
+impl<'a, T: 'a> LockTestExt<'a> for Mutex<T> {
#[inline]
fn held_by_thread(&self) -> LockHeldState {
LockMetadata::held_by_thread(&self.deps)
}
+ type ExclLock = MutexGuard<'a, T>;
+ #[inline]
+ fn unsafe_well_ordered_double_lock_self(&'a self) -> MutexGuard<T> {
+ LockMetadata::pre_lock(&self.deps, true);
+ self.inner.lock().map(|lock| MutexGuard { mutex: self, lock }).unwrap()
+ }
}
pub struct RwLock<T: Sized> {
pub struct RwLockReadGuard<'a, T: Sized + 'a> {
lock: &'a RwLock<T>,
- first_lock: bool,
guard: StdRwLockReadGuard<'a, T>,
}
impl<T: Sized> Drop for RwLockReadGuard<'_, T> {
fn drop(&mut self) {
- if !self.first_lock {
- // Note that its not strictly true that the first taken read lock will get unlocked
- // last, but in practice our locks are always taken as RAII, so it should basically
- // always be true.
- return;
- }
LOCKS_HELD.with(|held| {
held.borrow_mut().remove(&self.lock.deps.lock_idx);
});
}
pub fn read<'a>(&'a self) -> LockResult<RwLockReadGuard<'a, T>> {
- let first_lock = LockMetadata::pre_read_lock(&self.deps);
- self.inner.read().map(|guard| RwLockReadGuard { lock: self, guard, first_lock }).map_err(|_| ())
+ // Note that while we could be taking a recursive read lock here, Rust's `RwLock` may
+ // deadlock trying to take a second read lock if another thread is waiting on the write
+ // lock. This behavior is platform dependent, but our in-tree `FairRwLock` guarantees
+ // such a deadlock.
+ LockMetadata::pre_lock(&self.deps, false);
+ self.inner.read().map(|guard| RwLockReadGuard { lock: self, guard }).map_err(|_| ())
}
pub fn write<'a>(&'a self) -> LockResult<RwLockWriteGuard<'a, T>> {
- LockMetadata::pre_lock(&self.deps);
+ LockMetadata::pre_lock(&self.deps, false);
self.inner.write().map(|guard| RwLockWriteGuard { lock: self, guard }).map_err(|_| ())
}
}
}
-impl <T> LockTestExt for RwLock<T> {
+impl<'a, T: 'a> LockTestExt<'a> for RwLock<T> {
#[inline]
fn held_by_thread(&self) -> LockHeldState {
LockMetadata::held_by_thread(&self.deps)
}
+ type ExclLock = RwLockWriteGuard<'a, T>;
+ #[inline]
+ fn unsafe_well_ordered_double_lock_self(&'a self) -> RwLockWriteGuard<'a, T> {
+ LockMetadata::pre_lock(&self.deps, true);
+ self.inner.write().map(|guard| RwLockWriteGuard { lock: self, guard }).unwrap()
+ }
}
pub type FairRwLock<T> = RwLock<T>;
projects / rust-lightning / blobdiff