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Fix deadlock releasing TSFN after environment shutdown #480

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Fix deadlock releasing TSFN after environment shutdown #480

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14 changes: 12 additions & 2 deletions src/NodeApi/Interop/JSSynchronizationContext.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -247,13 +247,15 @@ public Task<T> RunAsync<T>(Func<Task<T>> asyncAction)
internal sealed class JSTsfnSynchronizationContext : JSSynchronizationContext
{
private readonly JSThreadSafeFunction _tsfn;
private bool _tsfnFinalized;

public JSTsfnSynchronizationContext()
{
_tsfn = new JSThreadSafeFunction(
maxQueueSize: 0,
initialThreadCount: 1,
asyncResourceName: (JSValue)nameof(JSSynchronizationContext));
asyncResourceName: (JSValue)nameof(JSSynchronizationContext),
finalize: _ => _tsfnFinalized = true);

// Unref TSFN to indicate that this TSFN is not preventing Node.JS shutdown.
_tsfn.Unref();
Expand All @@ -267,7 +269,15 @@ public override void Dispose()

// Destroy TSFN by releasing last thread use count.
// TSFN is deleted after this point and must not be used.
_tsfn.Release();
// During environment shutdown, Node.js finalizes the TSFN before the
// instance data finalizer disposes this context. Releasing it then
// deadlocks the JS thread on Node.js >= 24.14, where the release
// re-locks the TSFN mutex already held by the finalization path, and
// is a use-after-free on older versions.
if (!_tsfnFinalized)
{
_tsfn.Release();
}
}

/// <summary>
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