Share Windows thread-suspend and -resume code

This adds "suspend" and "resume" methods to windows_thread_info, and
changes gdb and gdbserver to share this code.

gdb/ChangeLog
2020-04-08  Tom Tromey  <tromey@adacore.com>

	* windows-nat.c (thread_rec): Use windows_thread_info::suspend.
	(windows_continue): Use windows_continue::resume.
	* nat/windows-nat.h (struct windows_thread_info) <suspend,
	resume>: Declare new methods.
	* nat/windows-nat.c: New file.
	* configure.nat (NATDEPFILES): Add nat/windows-nat.o when needed.

gdbserver/ChangeLog
2020-04-08  Tom Tromey  <tromey@adacore.com>

	* win32-low.c (win32_require_context, suspend_one_thread): Use
	windows_thread_info::suspend.
	(continue_one_thread): Use windows_thread_info::resume.
	* configure.srv (srv_tgtobj): Add windows-nat.o when needed.

5 files changed, 79 insertions, 26 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index c988594..bf1ef5b 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,14 @@
 2020-04-08  Tom Tromey  <tromey@adacore.com>
 
+	* windows-nat.c (thread_rec): Use windows_thread_info::suspend.
+	(windows_continue): Use windows_continue::resume.
+	* nat/windows-nat.h (struct windows_thread_info) <suspend,
+	resume>: Declare new methods.
+	* nat/windows-nat.c: New file.
+	* configure.nat (NATDEPFILES): Add nat/windows-nat.o when needed.
+
+2020-04-08  Tom Tromey  <tromey@adacore.com>
+
 	* windows-nat.c (windows_add_thread, windows_delete_thread)
 	(windows_nat_target::fetch_registers)
 	(windows_nat_target::store_registers, fake_create_process)
diff --git a/gdb/configure.nat b/gdb/configure.nat
index 83ffdb8..6ea2583 100644
--- a/gdb/configure.nat
+++ b/gdb/configure.nat
@@ -75,10 +75,10 @@ case ${gdb_host} in
 	NATDEPFILES='fork-child.o nat/fork-inferior.o inf-ptrace.o'
 	;;
     cygwin*)
-	NATDEPFILES='x86-nat.o nat/x86-dregs.o windows-nat.o'
+	NATDEPFILES='x86-nat.o nat/x86-dregs.o windows-nat.o nat/windows-nat.o'
 	;;
     mingw*)
-	NATDEPFILES='x86-nat.o nat/x86-dregs.o windows-nat.o'
+	NATDEPFILES='x86-nat.o nat/x86-dregs.o windows-nat.o nat/windows-nat.o'
 	;;
     aix)
 	NATDEPFILES='nat/fork-inferior.o fork-child.o inf-ptrace.o'
diff --git a/gdb/nat/windows-nat.c b/gdb/nat/windows-nat.c
new file mode 100644
index 0000000..a98ff42
--- /dev/null
+++ b/gdb/nat/windows-nat.c
@@ -0,0 +1,60 @@
+/* Internal interfaces for the Windows code
+   Copyright (C) 1995-2019 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include "gdbsupport/common-defs.h"
+#include "nat/windows-nat.h"
+
+void
+windows_thread_info::suspend ()
+{
+  if (suspended != 0)
+    return;
+
+  if (SuspendThread (h) == (DWORD) -1)
+    {
+      DWORD err = GetLastError ();
+
+      /* We get Access Denied (5) when trying to suspend
+	 threads that Windows started on behalf of the
+	 debuggee, usually when those threads are just
+	 about to exit.
+	 We can get Invalid Handle (6) if the main thread
+	 has exited.  */
+      if (err != ERROR_INVALID_HANDLE && err != ERROR_ACCESS_DENIED)
+	warning (_("SuspendThread (tid=0x%x) failed. (winerr %u)"),
+		 (unsigned) tid, (unsigned) err);
+      suspended = -1;
+    }
+  else
+    suspended = 1;
+}
+
+void
+windows_thread_info::resume ()
+{
+  if (suspended > 0)
+    {
+      if (ResumeThread (h) == (DWORD) -1)
+	{
+	  DWORD err = GetLastError ();
+	  warning (_("warning: ResumeThread (tid=0x%x) failed. (winerr %u)"),
+		   (unsigned) tid, (unsigned) err);
+	}
+    }
+  suspended = 0;
+}
diff --git a/gdb/nat/windows-nat.h b/gdb/nat/windows-nat.h
index 543de89..695f801 100644
--- a/gdb/nat/windows-nat.h
+++ b/gdb/nat/windows-nat.h
@@ -34,6 +34,12 @@ struct windows_thread_info
 
   DISABLE_COPY_AND_ASSIGN (windows_thread_info);
 
+  /* Ensure that this thread has been suspended.  */
+  void suspend ();
+
+  /* Resume the thread if it has been suspended.  */
+  void resume ();
+
   /* The Win32 thread identifier.  */
   DWORD tid;
 
diff --git a/gdb/windows-nat.c b/gdb/windows-nat.c
index d2e900c..da35799 100644
--- a/gdb/windows-nat.c
+++ b/gdb/windows-nat.c
@@ -416,27 +416,7 @@ thread_rec (DWORD id, int get_context)
 	if (!th->suspended && get_context)
 	  {
 	    if (get_context > 0 && id != current_event.dwThreadId)
-	      {
-		if (SuspendThread (th->h) == (DWORD) -1)
-		  {
-		    DWORD err = GetLastError ();
-
-		    /* We get Access Denied (5) when trying to suspend
-		       threads that Windows started on behalf of the
-		       debuggee, usually when those threads are just
-		       about to exit.
-		       We can get Invalid Handle (6) if the main thread
-		       has exited.  */
-		    if (err != ERROR_INVALID_HANDLE
-			&& err != ERROR_ACCESS_DENIED)
-		      warning (_("SuspendThread (tid=0x%x) failed."
-				 " (winerr %u)"),
-			       (unsigned) id, (unsigned) err);
-		    th->suspended = -1;
-		  }
-		else
-		  th->suspended = 1;
-	      }
+	      th->suspend ();
 	    else if (get_context < 0)
 	      th->suspended = -1;
 	    th->reload_context = true;
@@ -1515,9 +1495,7 @@ windows_continue (DWORD continue_status, int id, int killed)
 		th->context.ContextFlags = 0;
 	      }
 	  }
-	if (th->suspended > 0)
-	  (void) ResumeThread (th->h);
-	th->suspended = 0;
+	th->resume ();
       }
 
   res = ContinueDebugEvent (current_event.dwProcessId,