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fix(sync): harden pre-Vista condition waiters #1960

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Merged
jpnurmi merged 2 commits into from
Aug 6, 2026
+5 −3
Merged

fix(sync): harden pre-Vista condition waiters #1960

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6060d20
fix(sync): count pre-Vista waiters before unlocking
jpnurmi Aug 5, 2026
614de79
fix(sync): read pre-Vista waiters atomically
jpnurmi Aug 5, 2026
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8 changes: 5 additions & 3 deletions src/sentry_sync.h
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Original file line number Diff line number Diff line change
Expand Up @@ -99,9 +99,9 @@ SleepConditionVariableCS_PREVISTA(
{
DWORD result = 0;

InterlockedIncrement((LONG *)&cv->Waiters);
LeaveCriticalSection(cs);

InterlockedIncrement((LONG *)&cv->Waiters);
result = WaitForSingleObject(cv->Semaphore, timeout);

// send event only on target
Expand All @@ -122,12 +122,14 @@ WakeConditionVariable_PREVISTA(PCONDITION_VARIABLE_PREVISTA ConditionVariable)
return;
}

if (ConditionVariable->Waiters == 0) {
const LONG waiters = InterlockedCompareExchange(
(volatile LONG *)&ConditionVariable->Waiters, 0, 0);
if (waiters == 0) {
return;
}

// set target for continue event, alert it on first occurance
ConditionVariable->Target = ConditionVariable->Waiters - 1;
ConditionVariable->Target = waiters - 1;

SignalObjectAndWait(ConditionVariable->Semaphore,
ConditionVariable->ContinueEvent, INFINITE, FALSE);
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