runtime: [Windows] corefx tests are all timing out

The Windows x86 corefx test runs have almost all timed out (after 6 hours) since about Jan. 23.

https://ci.dot.net/job/dotnet_coreclr/job/master/view/x86/job/jitstress/job/x86_checked_windows_nt_corefx_baseline/

The last command run is:

build.cmd -test -Release /p:OSGroup=Windows_NT /p:ArchGroup=x86   /p:WithoutCategories=IgnoreForCI /p:PreExecutionTestScript=D:\j\workspace\x86_checked_w---fbe14ed2\SetStressModes.bat

(SetStressModes.bat just contains set COMPlus_TieredCompilation=0)

From the log file, it looks like all time is taken by Microsoft.Win32.SystemEventsTests. Here’s a log fragment:

14:55:16      Microsoft.Win32.SystemEvents.Tests: [Long Running Test] 'Microsoft.Win32.SystemEventsTests.PowerModeTests.SignalsPowerModeChanged', Elapsed: 05:32:57
14:55:16   [Long Running Test] 'Microsoft.Win32.SystemEventsTests.SessionEndedTests.SignalsSessionEnded', Elapsed: 05:32:57
14:55:16   [Long Running Test] 'Microsoft.Win32.SystemEventsTests.CreateTimerTests.ConcurrentTimers', Elapsed: 05:32:57
14:55:16   [Long Running Test] 'Microsoft.Win32.SystemEventsTests.UserPreferenceTests.SignalsUserPreferenceEventsAsynchronously', Elapsed: 05:32:57
14:57:15      Microsoft.Win32.SystemEvents.Tests: [Long Running Test] 'Microsoft.Win32.SystemEventsTests.PowerModeTests.SignalsPowerModeChanged', Elapsed: 05:34:57
14:57:15   [Long Running Test] 'Microsoft.Win32.SystemEventsTests.SessionEndedTests.SignalsSessionEnded', Elapsed: 05:34:57
14:57:15   [Long Running Test] 'Microsoft.Win32.SystemEventsTests.CreateTimerTests.ConcurrentTimers', Elapsed: 05:34:57
14:57:15   [Long Running Test] 'Microsoft.Win32.SystemEventsTests.UserPreferenceTests.SignalsUserPreferenceEventsAsynchronously', Elapsed: 05:34:57

The stress modes have the same behavior, e.g., https://ci.dot.net/job/dotnet_coreclr/job/master/view/x86/job/jitstress/job/x86_checked_windows_nt_corefx_jitstress1/ https://ci.dot.net/job/dotnet_coreclr/job/master/view/x86/job/jitstress/job/x86_checked_windows_nt_corefx_jitstress2/