Cygwin: timerfd: add a sleep when being debugged

A sleep is required on Windows 10 64 bit only before calling
RegisterClassW in the timerfd thread, and only when running
under strace.  One of the child processes inheriting the timerfd
descriptor will get a STATUS_FLOAT_INEXACT_RESULT exception inside
of msvcrt.dll.  It's apparently some timing problem.  It occurs
in 4 out of 5 runs under strace only.  WOW64 and Windows 7 64 bit
don't have this problem.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

1 files changed, 9 insertions, 0 deletions

diff --git a/winsup/cygwin/timerfd.cc b/winsup/cygwin/timerfd.cc
index b0d4db9..8e4c94e 100644
--- a/winsup/cygwin/timerfd.cc
+++ b/winsup/cygwin/timerfd.cc
@@ -32,6 +32,15 @@ timerfd_tracker::create_timechange_window ()
   wclass.lpfnWndProc = DefWindowProcW;
   wclass.hInstance = user_data->hmodule;
   wclass.lpszClassName = cname;
+  /* This sleep is required on Windows 10 64 bit only, and only when running
+     under strace.  One of the child processes inheriting the timerfd
+     descriptor will get a STATUS_FLOAT_INEXACT_RESULT exception inside of
+     msvcrt.dll.  While this is completely crazy in itself, it's apparently
+     some timing problem.  It occurs in 4 out of 5 runs under strace only.
+     The sleep is required before calling RegisterClassW.  Moving it before
+     CreateWindowExW does not work.  What the heck? */
+  if (being_debugged ())
+    Sleep (1L);
   atom = RegisterClassW (&wclass);
   if (!atom)
     debug_printf ("RegisterClass %E");