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The mono changes look ok.

Here are some perf numbers on NativeAOT. I used a test that has multiple threads enter a lock, perform a short delay, exit the lock, and perform another short delay. Throughput is the number of enter+delay+exit+delay rounds performed per ms. The delay is a recursive calculation of a random Fibonacci number between 4 and 9. The numbers are from my Intel x64 6-core 12-thread machine on Windows.

UsingMonitor:

UsingLock:

Rebased to fix conflicts

/azp run runtime-extra-platforms

Trying a rebase due to some unrelated build failures.

The remaining issues in the CI appear to be unrelated.

This was merged on Red and broke Wasm.Build.Tests onmain.#94212

Also one of thefailures is:

Unhandled exception. System.InvalidOperationException: There is no currently active test.   at Xunit.Sdk.TestOutputHelper.QueueTestOutput(String output) in /_/src/xunit.execution/Sdk/Frameworks/TestOutputHelper.cs:line 60   at System.Diagnostics.AsyncStreamReader.FlushMessageQueue(Boolean rethrowInNewThread)--- End of stack trace from previous location ---   at System.Threading.ThreadPoolWorkQueue.Dispatch()   at System.Threading.PortableThreadPool.WorkerThread.WorkerThreadStart()./RunTests.sh: line 105:    83 Aborted                 (core dumped) dotnet exec xunit.console.dll Wasm.Build.Tests.dll -xml $XHARNESS_OUT/testResults.xml $HELIX_XUNIT_ARGS -nocolor -verbose -notrait category=IgnoreForCI -notrait category=failing $XUnitTraitArg $RSP_FILE

Could this be related to the change here? I have never seen this happen on the tests before.

cc@lewing

Also introduced#94227

This was merged on Red and broke Wasm.Build.Tests on main.#94212
Could this be related to the change here? I have never seen this happen on the tests before.

I have no idea how this PR could cause those failures, apologies if there was a mishap. There are only a few lines of code in this PR that would affect wasm, do you see anything that could be relevant? I'll see if I can get a repro, but otherwise I don't see any link between the failure and this PR.

Also introduced#94227

#94241 should fix the issue.

Could this be related to the change here? I have never seen this happen on the tests before.

Only thing I can think of at the moment is that there is a pragma warning disable for using preview features when we should probably be enabling preview features for the corelib project. I don't know what kind of effect that would have, but I think that's something that was missed after local testing and unaddressed, so I'll fix that anyway.