[newlib-cygwin/main] Cygwin: revert use of CancelSyncronousIo on wait_thread.

[Corinna Vinschen]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=6614da9a71fc5cf24991b47fd62a56749c7f4ccc

commit 6614da9a71fc5cf24991b47fd62a56749c7f4ccc
Author:     Jeremy Drake <cygwin@jdrake.com>
AuthorDate: Sat Nov 23 08:37:25 2024 -0800
Commit:     Corinna Vinschen <corinna@vinschen.de>
CommitDate: Mon Nov 25 12:22:51 2024 +0100

    Cygwin: revert use of CancelSyncronousIo on wait_thread.
    
    It appears this is causing hangs on native x86_64 in similar scenarios
    as the hangs on ARM64, because `CancelSynchronousIo` is returning `TRUE`
    but not canceling the `ReadFile` call as expected.
    
    Addresses: https://github.com/msys2/MSYS2-packages/issues/4340#issuecomment-2491401847
    Fixes: b091b47b9e56 ("cygthread: suspend thread before terminating.")
    Signed-off-by: Jeremy Drake <cygwin@jdrake.com>

Diff:
---
 winsup/cygwin/pinfo.cc   | 10 +++-------
 winsup/cygwin/sigproc.cc | 12 ++----------
 2 files changed, 5 insertions(+), 17 deletions(-)

diff --git a/winsup/cygwin/pinfo.cc b/winsup/cygwin/pinfo.cc
index f1db71595181..e31a67d8f412 100644
--- a/winsup/cygwin/pinfo.cc
+++ b/winsup/cygwin/pinfo.cc
@@ -1252,17 +1252,13 @@ proc_waiter (void *arg)
 
   for (;;)
     {
-      DWORD nb, err;
+      DWORD nb;
       char buf = '\0';
 
       if (!ReadFile (vchild.rd_proc_pipe, &buf, 1, &nb, NULL)
-	  && (err = GetLastError ()) != ERROR_BROKEN_PIPE)
+	  && GetLastError () != ERROR_BROKEN_PIPE)
 	{
-	  /* ERROR_OPERATION_ABORTED is expected due to the possibility that
-	     CancelSynchronousIo interruped the ReadFile call, so don't output
-	     that error */
-	  if (err != ERROR_OPERATION_ABORTED)
-	    system_printf ("error on read of child wait pipe %p, %E", vchild.rd_proc_pipe);
+	  system_printf ("error on read of child wait pipe %p, %E", vchild.rd_proc_pipe);
 	  break;
 	}
 
diff --git a/winsup/cygwin/sigproc.cc b/winsup/cygwin/sigproc.cc
index 9e20ae6f71c0..81b6c316956a 100644
--- a/winsup/cygwin/sigproc.cc
+++ b/winsup/cygwin/sigproc.cc
@@ -409,11 +409,7 @@ proc_terminate ()
 	     to 1 iff it is a Cygwin process.  */
 	  if (!have_execed || !have_execed_cygwin)
 	    chld_procs[i]->ppid = 1;
-	  /* Attempt to exit the wait_thread cleanly via CancelSynchronousIo
-	     before falling back to the (explicitly dangerous) cross-thread
-	     termination */
-	  if (chld_procs[i].wait_thread
-	      && !CancelSynchronousIo (chld_procs[i].wait_thread->thread_handle ()))
+	  if (chld_procs[i].wait_thread)
 	    chld_procs[i].wait_thread->terminate_thread ();
 	  /* Release memory associated with this process unless it is 'myself'.
 	     'myself' is only in the chld_procs table when we've execed.  We
@@ -1178,11 +1174,7 @@ remove_proc (int ci)
 {
   if (have_execed)
     {
-      /* Attempt to exit the wait_thread cleanly via CancelSynchronousIo
-	 before falling back to the (explicitly dangerous) cross-thread
-	 termination */
-      if (_my_tls._ctinfo != chld_procs[ci].wait_thread
-	  && !CancelSynchronousIo (chld_procs[ci].wait_thread->thread_handle ()))
+      if (_my_tls._ctinfo != chld_procs[ci].wait_thread)
 	chld_procs[ci].wait_thread->terminate_thread ();
     }
   else if (chld_procs[ci] && chld_procs[ci]->exists ())