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Start thread pool worker threads in the default execution context #46181

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merged 10 commits into from
Dec 19, 2020
Merged

Start thread pool worker threads in the default execution context #46181

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b53cc03
Start thread pool worker threads in the default execution context
kouvel Dec 13, 2020
b9684d4
Simplify EC changes as suggested
kouvel Dec 17, 2020
1059217
Revert to using `Capture` to prevent flow-suppressed ECs from flowing
kouvel Dec 17, 2020
15415e3
Add test, similarly fix gate thread and wait thread creations, minor …
kouvel Dec 17, 2020
5b29acc
Minor undo of minor changes before
kouvel Dec 17, 2020
d3e9029
Add test to verify EC flow to new threads
kouvel Dec 17, 2020
f58e178
Update thread creation in Mono to flow EC
kouvel Dec 18, 2020
65222e2
Add internal `Thread.UnsafeStart` that does not propagate the EC and …
kouvel Dec 18, 2020
b97b0fe
Clear saved EC before calling start callback
kouvel Dec 18, 2020
caf5e21
Similarly update portable implementation of timer
kouvel Dec 18, 2020
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7 changes: 3 additions & 4 deletions src/coreclr/System.Private.CoreLib/src/System/Threading/Thread.CoreCLR.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -70,7 +70,7 @@ internal void ThreadStart(object? obj)
_startArg = obj;

ExecutionContext? context = _executionContext;
if (context != null)
if (context != null && !context.IsDefault)
{
ExecutionContext.RunInternal(context, s_threadStartContextCallback, this);
}
Expand All @@ -87,7 +87,7 @@ internal void ThreadStart()
Debug.Assert(_start is ThreadStart);

ExecutionContext? context = _executionContext;
if (context != null)
if (context != null && !context.IsDefault)
{
ExecutionContext.RunInternal(context, s_threadStartContextCallback, this);
}
Expand Down Expand Up @@ -222,8 +222,7 @@ public void Start()
Debug.Assert(_delegate.Target is ThreadHelper);
var t = (ThreadHelper)_delegate.Target;

ExecutionContext? ec = ExecutionContext.Capture();
t.SetExecutionContextHelper(ec);
t.SetExecutionContextHelper(CurrentThread._executionContext);
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}

StartInternal();
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27 changes: 23 additions & 4 deletions src/libraries/System.Private.CoreLib/src/System/Threading/PortableThreadPool.WorkerThread.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -288,10 +288,28 @@ private static bool TryCreateWorkerThread()
{
try
{
Thread workerThread = new Thread(WorkerThreadStart);
workerThread.IsThreadPoolThread = true;
workerThread.IsBackground = true;
workerThread.Start();
// Starting a new thread transfers the current execution context to the new thread. Worker threads must
// start in the default context, so switch contexts temporarily if necessary.
Thread currentThread = Thread.CurrentThread;
ExecutionContext? previousExecutionContext = currentThread._executionContext;
currentThread._executionContext = null;

try
{
Thread workerThread = new Thread(WorkerThreadStart);
workerThread.IsThreadPoolThread = true;
workerThread.IsBackground = true;
workerThread.Start();
}
catch
{
// Note: we have a "catch" rather than a "finally" because we want to stop the first pass of EH here.
// That way we can restore the previous context before any of our callers' EH filters run.
currentThread._executionContext = previousExecutionContext;
throw;
}

currentThread._executionContext = previousExecutionContext;
}
catch (ThreadStartException)
{
Expand All @@ -301,6 +319,7 @@ private static bool TryCreateWorkerThread()
{
return false;
}

return true;
}
}
Expand Down