The Unix implementation of Process type is not thread safe

[tmat]

Description

Method GetWaitState() may be entered my multiple threads (it's not guarded by a lock) and each thread can return different instance of the ProcessWaitState, which is mutable.

runtime/src/libraries/System.Diagnostics.Process/src/System/Diagnostics/Process.Unix.cs

Lines 955 to 962 in 97f5045

	{
	if (_waitStateHolder == null)
	{
	EnsureState(State.HaveId);
	_waitStateHolder = new ProcessWaitState.Holder(_processId);
	}
	return _waitStateHolder._state;
	}

When using Process.Kill in dotnet-watch we observed that the method sometimes failed to terminate process on Linux. It is plausible that this is due to the above race condition.

Reproduction Steps

n/a

Expected behavior

All methods of Process type should be thread safe.

Actual behavior

Race conditions

Regression?

No response

Known Workarounds

No response

Configuration

No response

Other information

No response

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