[RuntimeAsync] NullReferenceException crash in some scenarios in System.Text.Json.Serialization.Tests.PipeTests #121564
Description
The failure only happens on Linux and the number of failures is not stable - sometimes I see 2 sometimes 4. Locally I typically see 4.
I suspect we have some kind of GC hole.
Example of a failure in the CI:
https://helixr1107v0xdcypoyl9e7f.blob.core.windows.net/dotnet-runtime-refs-pull-119432-merge-985956b1db93433192/System.Text.Json.Tests/1/console.fe1637fd.log?helixlogtype=result
The problem code looks like:
internal async ValueTask<T?> DeserializeAsync<TReadBufferState, TStream>(TStream utf8Json, TReadBufferState bufferState, CancellationToken cancellationToken)
where TReadBufferState : struct, IReadBufferState<TReadBufferState, TStream>
{
Debug.Assert(IsConfigured);
JsonSerializerOptions options = Options;
ReadStack readStack = default;
readStack.Initialize(this, supportContinuation: true);
var jsonReaderState = new JsonReaderState(options.GetReaderOptions());
try
{
while (true)
{
bufferState = await bufferState.ReadAsync(utf8Json, cancellationToken).ConfigureAwait(false);
bool success = ContinueDeserialize<TReadBufferState, TStream>(
ref bufferState,
ref jsonReaderState,
ref readStack,
out T? value);
if (success)
{
return value;
}
}
}
finally
{
bufferState.Dispose();
}
}Right before the await the bufferState._utf8Json is not null. Once cancelation exception is thrown, we get to finally, which calls bufferState.Dispose().
Inside bufferState.Dispose() the bufferState._utf8Json is somehow null and _utf8Json.AdvanceTo(_sequence.Start); throws NRE.
The result is failures like:
System.Text.Json.Serialization.Tests.PipeTests+PipeTests_AsyncWithSmallBuffer.CancelPendingReadThrows [FAIL]
Assert.Throws() Failure: Exception type was not an exact match
Expected: typeof(System.OperationCanceledException)
Actual: typeof(System.NullReferenceException)
---- System.NullReferenceException : Object reference not set to an instance of an object.
Stack Trace:
/_/src/libraries/System.Text.Json/tests/System.Text.Json.Tests/Serialization/Pipe.ReadTests.cs(97,0): at System.Text.Json.Serialization.Tests.PipeTests.CancelPendingReadThrows()
--- End of stack trace from previous location ---
--- End of stack trace from previous location ---
----- Inner Stack Trace -----
/_/src/libraries/System.Text.Json/src/System/Text/Json/Serialization/PipeReadBufferState.cs(149,0): at System.Text.Json.Serialization.PipeReadBufferState.Dispose()
/_/src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Metadata/JsonTypeInfoOfT.ReadHelper.cs(54,0): at System.Text.Json.Serialization.Metadata.JsonTypeInfo`1.DeserializeAsync[TReadBufferState,TStream](TStream utf8Json, TReadBufferState bufferState, CancellationToken cancellationToken)
/_/src/coreclr/System.Private.CoreLib/src/System/Runtime/CompilerServices/AsyncHelpers.CoreCLR.cs(467,0): at System.Runtime.CompilerServices.AsyncHelpers.RuntimeAsyncTaskCore.DispatchContinuations[T,TOps](T task)
--- End of stack trace from previous location ---
/_/src/libraries/System.Private.CoreLib/src/System/Runtime/CompilerServices/AsyncHelpers.cs(99,0): at System.Runtime.CompilerServices.AsyncHelpers.Await(Task task)
at System.Text.Json.Serialization.Tests.PipeTests.<>c__DisplayClass4_0.<CancelPendingReadThrows>b__0()
--- End of stack trace from previous location ---