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Fix ABA and UAF problem in ConditionVariable notify operation using internal spinlock (#458) #459

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Merged
ChuanqiXu9 merged 4 commits into from
Mar 17, 2026
+25 −11
Merged

Fix ABA and UAF problem in ConditionVariable notify operation using internal spinlock (#458) #459

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dff885a
Fix ABA problem in ConditionVariable::notifyOne using internal spinlo…
fanfanffy163 Mar 16, 2026
e134952
Fix UAF and ABA in ConditionVariable notify using SpinLock (Fixes #458)
fanfanffy163 Mar 16, 2026
2ed1b5c
fix(ci): resolve clang-format warnings and C++20 module dependency
fanfanffy163 Mar 16, 2026
6864dcf
style: bypass clang-format for module dependency order
fanfanffy163 Mar 16, 2026
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4 changes: 3 additions & 1 deletion async_simple/async_simple.cppm
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Original file line number Diff line number Diff line change
Expand Up @@ -58,8 +58,10 @@ export extern "C++" {
#include "uthread/internal/thread.h"
#include "uthread/Uthread.h"
#include "uthread/Async.h"
#include "coro/ConditionVariable.h"
// clang-format off
#include "coro/SpinLock.h"
#include "coro/ConditionVariable.h"
// clang-format on
#include "coro/Latch.h"
#include "coro/CountEvent.h"
#include "coro/Collect.h"
Expand Down
32 changes: 22 additions & 10 deletions async_simple/coro/ConditionVariable.h
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,7 @@
#ifndef ASYNC_SIMPLE_USE_MODULES
#include <mutex>
#include "async_simple/coro/Lazy.h"
#include "async_simple/coro/SpinLock.h"

#endif // ASYNC_SIMPLE_USE_MODULES

Expand Down Expand Up @@ -50,6 +51,7 @@ class ConditionVariable {
private:
friend class ConditionVariableAwaiter<Lock>;
std::atomic<ConditionVariableAwaiter<Lock>*> _awaiters = nullptr;
SpinLock _notifyLock;
};

template <class Lock>
Expand Down Expand Up @@ -94,21 +96,31 @@ inline Lazy<> ConditionVariable<Lock>::wait(Lock& lock, Pred&& pred) noexcept {

template <class Lock>
inline void ConditionVariable<Lock>::notifyAll() noexcept {
auto awaitings = _awaiters.load(std::memory_order_acquire);
while (!_awaiters.compare_exchange_weak(awaitings, nullptr,
std::memory_order_acq_rel,
std::memory_order_acquire))
;
ConditionVariableAwaiter<Lock>* awaitings = nullptr;
{
ScopedSpinLock notifyLock(_notifyLock);
awaitings = _awaiters.load(std::memory_order_acquire);
while (!_awaiters.compare_exchange_weak(awaitings, nullptr,
std::memory_order_acq_rel,
std::memory_order_acquire))
;
}
resumeWaiters(awaitings);
}

template <class Lock>
inline void ConditionVariable<Lock>::notifyOne() noexcept {
auto awaitings = _awaiters.load(std::memory_order_acquire);
while (awaitings && !_awaiters.compare_exchange_weak(awaitings, awaitings->_next,
std::memory_order_acq_rel,
std::memory_order_acquire))
;
ConditionVariableAwaiter<Lock>* awaitings = nullptr;
{
ScopedSpinLock notifyLock(_notifyLock);
awaitings = _awaiters.load(std::memory_order_acquire);
while (awaitings &&
!_awaiters.compare_exchange_weak(awaitings, awaitings->_next,
std::memory_order_acq_rel,
std::memory_order_acquire))
;
}

if (!awaitings) {
return;
}
Expand Down
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