Windows gdbserver: Eliminate soft-interrupt mechanism

I noticed that faked_breakpoint is write only.  And then I hacked
win32_process_target::request_interrupt to force it to stop threads
using the soft_interrupt_requested mechanism (which suspends threads,
and then fakes a breakpoint event in the main thread), and saw that it
no longer works -- gdbserver crashes accessing a NULL current_thread,
because fake_breakpoint_event does not switch to a thread.

This code was originally added for Windows CE, as neither
GenerateConsoleCtrlEvent nor DebugBreakProcess worked there.  Windows
CE support has since been removed.

We nowadays require Windows XP or later, and XP has DebugBreakProcess.

The soft_interrupt_requested mechanism has other problems, like for
example faking the event in the main thread, even if that thread was
previously stopped, due to scheduler-locking.

A following patch will add a similar mechanism stopping all threads
with SuspendThread to native GDB, for non-stop mode, which doesn't
have these problems.  It's different enough from this old code that I
think we should just rip the old code out, and reimplement it from
scratch (based on gdb's version) when we need it.

Approved-By: Tom Tromey <tom@tromey.com>
Change-Id: I89e98233a9c40c6dcba7c8e1dacee08603843fb1

diff --git a/gdbserver/win32-low.cc b/gdbserver/win32-low.cc
index 2e3e4442012d3e2ebdbdc44afa684319983b3da5..ebce67cd72df0330818d6ef2f83d2ef6d483047d 100644 (file)
--- a/gdbserver/win32-low.cc
+++ b/gdbserver/win32-low.cc
@@ -294,8 +294,6 @@ do_initial_child_stuff (HANDLE proch, DWORD pid, int attached)
   windows_process.process_id = pid;
   windows_process.main_thread_id = 0;
 
-  windows_process.soft_interrupt_requested = 0;
-  windows_process.faked_breakpoint = 0;
   windows_process.open_process_used = true;
 
   memset (&windows_process.current_event, 0,
@@ -418,7 +416,6 @@ child_continue_for_kill (DWORD continue_status, int thread_id)
     {
       continue_one_thread (thread, thread_id);
     });
-  windows_process.faked_breakpoint = 0;
 
   return continue_last_debug_event (continue_status, debug_threads);
 }
@@ -918,23 +915,6 @@ suspend_one_thread (thread_info *thread)
   th->suspend ();
 }
 
-static void
-fake_breakpoint_event (void)
-{
-  OUTMSG2(("fake_breakpoint_event\n"));
-
-  windows_process.faked_breakpoint = 1;
-
-  memset (&windows_process.current_event, 0,
-         sizeof (windows_process.current_event));
-  windows_process.current_event.dwThreadId = windows_process.main_thread_id;
-  windows_process.current_event.dwDebugEventCode = EXCEPTION_DEBUG_EVENT;
-  windows_process.current_event.u.Exception.ExceptionRecord.ExceptionCode
-    = EXCEPTION_BREAKPOINT;
-
-  for_each_thread (suspend_one_thread);
-}
-
 /* See nat/windows-nat.h.  */
 
 bool
@@ -989,13 +969,6 @@ get_child_debug_event (DWORD *continue_status,
 
   DEBUG_EVENT *current_event = &windows_process.current_event;
 
-  if (windows_process.soft_interrupt_requested)
-    {
-      windows_process.soft_interrupt_requested = 0;
-      fake_breakpoint_event ();
-      goto gotevent;
-    }
-
   windows_process.attaching = 0;
   {
     process_info *proc = find_process_pid (windows_process.process_id);
@@ -1036,8 +1009,6 @@ get_child_debug_event (DWORD *continue_status,
       }
   }
 
- gotevent:
-
   switch (current_event->dwDebugEventCode)
     {
     case CREATE_THREAD_DEBUG_EVENT:
@@ -1291,8 +1262,7 @@ win32_process_target::request_interrupt ()
   if (DebugBreakProcess (windows_process.handle))
     return;
 
-  /* Last resort, suspend all threads manually.  */
-  windows_process.soft_interrupt_requested = 1;
+  OUTMSG2 (("Could not interrupt.\n"));
 }
 
 bool

diff --git a/gdbserver/win32-low.h b/gdbserver/win32-low.h
index 3c49ca7de9b8343c6ce8e3246599fc563437f164..b170eb898f6df08ec1eeda9cc2ece62bef04afa2 100644 (file)
--- a/gdbserver/win32-low.h
+++ b/gdbserver/win32-low.h
@@ -194,14 +194,6 @@ struct gdbserver_windows_process : public windows_nat::windows_process_info
      debug event off the win32 API.  */
   struct target_waitstatus cached_status;
 
-  /* Non zero if an interrupt request is to be satisfied by suspending
-     all threads.  */
-  int soft_interrupt_requested = 0;
-
-  /* Non zero if the inferior is stopped in a simulated breakpoint done
-     by suspending all the threads.  */
-  int faked_breakpoint = 0;
-
   /* True if current_process_handle needs to be closed.  */
   bool open_process_used = false;