Windows gdb+gdbserver: New find_thread, replaces thread_rec(DONT_INVALIDATE_CONTEXT)

The goal of the next few patches is to eliminate thread_rec
completely.  This is the first patch in that effort.

thread_rec(DONT_INVALIDATE_CONTEXT) is really just a thread lookup
with no side effects, so this adds a find_thread function that lets
you do that.

Change-Id: Ie486badce00e234b10caa478b066c34537103e3f

5 files changed, 60 insertions, 55 deletions

diff --git a/gdb/nat/windows-nat.c b/gdb/nat/windows-nat.c
index f9f6848..46fbc2b 100644
--- a/gdb/nat/windows-nat.c
+++ b/gdb/nat/windows-nat.c
@@ -325,9 +325,8 @@ windows_process_info::handle_ms_vc_exception (const EXCEPTION_RECORD *rec)
       if (named_thread_id == (DWORD) -1)
 	named_thread_id = current_event.dwThreadId;
 
-      named_thread = thread_rec (ptid_t (current_event.dwProcessId,
-					 named_thread_id, 0),
-				 DONT_INVALIDATE_CONTEXT);
+      named_thread = find_thread (ptid_t (current_event.dwProcessId,
+					  named_thread_id, 0));
       if (named_thread != NULL)
 	{
 	  int thread_name_len;
diff --git a/gdb/nat/windows-nat.h b/gdb/nat/windows-nat.h
index 3783f39..9e8c87e 100644
--- a/gdb/nat/windows-nat.h
+++ b/gdb/nat/windows-nat.h
@@ -105,9 +105,6 @@ struct windows_thread_info
 /* Possible values to pass to 'thread_rec'.  */
 enum thread_disposition_type
 {
-  /* Do not invalidate the thread's context, and do not suspend the
-     thread.  */
-  DONT_INVALIDATE_CONTEXT,
   /* Invalidate the context, but do not suspend the thread.  */
   DONT_SUSPEND,
   /* Invalidate the context and suspend the thread.  */
@@ -178,6 +175,10 @@ struct windows_process_info
   bool ignore_first_breakpoint = false;
 #endif
 
+  /* Find a thread record given a thread id.
+
+     This function must be supplied by the embedding application.  */
+  virtual windows_thread_info *find_thread (ptid_t ptid) = 0;
 
   /* Find a thread record given a thread id.  THREAD_DISPOSITION
      controls whether the thread is suspended, and whether the context
diff --git a/gdb/windows-nat.c b/gdb/windows-nat.c
index 0102511..3a3dad5 100644
--- a/gdb/windows-nat.c
+++ b/gdb/windows-nat.c
@@ -90,6 +90,7 @@ struct windows_solib
 
 struct windows_per_inferior : public windows_process_info
 {
+  windows_thread_info *find_thread (ptid_t ptid) override;
   windows_thread_info *thread_rec (ptid_t ptid,
 				   thread_disposition_type disposition) override;
   int handle_output_debug_string (struct target_waitstatus *ourstatus) override;
@@ -257,8 +258,7 @@ struct windows_nat_target final : public x86_nat_target<inf_child_target>
 
   bool stopped_by_sw_breakpoint () override
   {
-    windows_thread_info *th
-      = windows_process.thread_rec (inferior_ptid, DONT_INVALIDATE_CONTEXT);
+    windows_thread_info *th = windows_process.find_thread (inferior_ptid);
     return th->stopped_at_software_breakpoint;
   }
 
@@ -515,34 +515,36 @@ windows_nat_target::wait_for_debug_event_main_thread (DEBUG_EVENT *event)
 /* See nat/windows-nat.h.  */
 
 windows_thread_info *
-windows_per_inferior::thread_rec
-     (ptid_t ptid, thread_disposition_type disposition)
+windows_per_inferior::find_thread (ptid_t ptid)
 {
   for (auto &th : thread_list)
     if (th->tid == ptid.lwp ())
-      {
-	if (!th->suspended)
-	  {
-	    switch (disposition)
-	      {
-	      case DONT_INVALIDATE_CONTEXT:
-		/* Nothing.  */
-		break;
-	      case INVALIDATE_CONTEXT:
-		if (ptid.lwp () != current_event.dwThreadId)
-		  th->suspend ();
-		th->reload_context = true;
-		break;
-	      case DONT_SUSPEND:
-		th->reload_context = true;
-		th->suspended = -1;
-		break;
-	      }
-	  }
-	return th.get ();
-      }
+      return th.get ();
+  return nullptr;
+}
 
-  return NULL;
+windows_thread_info *
+windows_per_inferior::thread_rec
+     (ptid_t ptid, thread_disposition_type disposition)
+{
+  windows_thread_info *th = find_thread (ptid);
+
+  if (th != nullptr && !th->suspended)
+    {
+      switch (disposition)
+	{
+	case INVALIDATE_CONTEXT:
+	  if (ptid.lwp () != current_event.dwThreadId)
+	    th->suspend ();
+	  th->reload_context = true;
+	  break;
+	case DONT_SUSPEND:
+	  th->reload_context = true;
+	  th->suspended = -1;
+	  break;
+	}
+    }
+  return th;
 }
 
 /* Add a thread to the thread list.
@@ -561,7 +563,7 @@ windows_nat_target::add_thread (ptid_t ptid, HANDLE h, void *tlb,
 
   gdb_assert (ptid.lwp () != 0);
 
-  if ((th = windows_process.thread_rec (ptid, DONT_INVALIDATE_CONTEXT)))
+  if ((th = windows_process.find_thread (ptid)))
     return th;
 
   CORE_ADDR base = (CORE_ADDR) (uintptr_t) tlb;
@@ -1149,7 +1151,7 @@ display_selectors (const char * args, int from_tty)
     }
 
   windows_thread_info *current_windows_thread
-    = windows_process.thread_rec (inferior_ptid, DONT_INVALIDATE_CONTEXT);
+    = windows_process.find_thread (inferior_ptid);
 
   if (!args)
     {
@@ -1426,7 +1428,7 @@ windows_nat_target::resume (ptid_t ptid, int step, enum gdb_signal sig)
 	      ptid.pid (), (unsigned) ptid.lwp (), step, sig);
 
   /* Get context for currently selected thread.  */
-  th = windows_process.thread_rec (inferior_ptid, DONT_INVALIDATE_CONTEXT);
+  th = windows_process.find_thread (inferior_ptid);
   if (th)
     {
 #ifdef __x86_64__
@@ -3119,7 +3121,7 @@ windows_nat_target::get_tib_address (ptid_t ptid, CORE_ADDR *addr)
 {
   windows_thread_info *th;
 
-  th = windows_process.thread_rec (ptid, DONT_INVALIDATE_CONTEXT);
+  th = windows_process.find_thread (ptid);
   if (th == NULL)
     return false;
 
@@ -3140,9 +3142,7 @@ windows_nat_target::get_ada_task_ptid (long lwp, ULONGEST thread)
 const char *
 windows_nat_target::thread_name (struct thread_info *thr)
 {
-  windows_thread_info *th
-    = windows_process.thread_rec (thr->ptid,
-				  DONT_INVALIDATE_CONTEXT);
+  windows_thread_info *th = windows_process.find_thread (thr->ptid);
   return th->thread_name ();
 }
 
@@ -3282,8 +3282,7 @@ cygwin_set_dr7 (unsigned long val)
 static CORE_ADDR
 cygwin_get_dr (int i)
 {
-  windows_thread_info *th
-    = windows_process.thread_rec (inferior_ptid, DONT_INVALIDATE_CONTEXT);
+  windows_thread_info *th = windows_process.find_thread (inferior_ptid);
 
 #ifdef __x86_64__
   if (windows_process.wow64_process)
@@ -3356,8 +3355,7 @@ windows_nat_target::thread_alive (ptid_t ptid)
 {
   gdb_assert (ptid.lwp () != 0);
 
-  windows_thread_info *th
-    = windows_process.thread_rec (ptid, DONT_INVALIDATE_CONTEXT);
+  windows_thread_info *th = windows_process.find_thread (ptid);
   return WaitForSingleObject (th->h, 0) != WAIT_OBJECT_0;
 }
 
diff --git a/gdbserver/win32-low.cc b/gdbserver/win32-low.cc
index cc314df..5a57eed 100644
--- a/gdbserver/win32-low.cc
+++ b/gdbserver/win32-low.cc
@@ -142,6 +142,17 @@ win32_require_context (windows_thread_info *th)
 /* See nat/windows-nat.h.  */
 
 windows_thread_info *
+gdbserver_windows_process::find_thread (ptid_t ptid)
+{
+  thread_info *thread = find_thread_ptid (ptid);
+  if (thread == nullptr)
+    return nullptr;
+  return (windows_thread_info *) thread_target_data (thread);
+}
+
+/* See nat/windows-nat.h.  */
+
+windows_thread_info *
 gdbserver_windows_process::thread_rec
      (ptid_t ptid, thread_disposition_type disposition)
 {
@@ -150,8 +161,7 @@ gdbserver_windows_process::thread_rec
     return NULL;
 
   windows_thread_info *th = (windows_thread_info *) thread_target_data (thread);
-  if (disposition != DONT_INVALIDATE_CONTEXT)
-    win32_require_context (th);
+  win32_require_context (th);
   return th;
 }
 
@@ -162,7 +172,7 @@ child_add_thread (DWORD pid, DWORD tid, HANDLE h, void *tlb)
   windows_thread_info *th;
   ptid_t ptid = ptid_t (pid, tid, 0);
 
-  if ((th = windows_process.thread_rec (ptid, DONT_INVALIDATE_CONTEXT)))
+  if ((th = windows_process.find_thread (ptid)))
     return th;
 
   CORE_ADDR base = (CORE_ADDR) (uintptr_t) tlb;
@@ -822,7 +832,7 @@ win32_process_target::resume (thread_resume *resume_info, size_t n)
 
   /* Get context for the currently selected thread.  */
   ptid = debug_event_ptid (&windows_process.current_event);
-  th = windows_process.thread_rec (ptid, DONT_INVALIDATE_CONTEXT);
+  th = windows_process.find_thread (ptid);
   if (th)
     {
       win32_prepare_to_resume (th);
@@ -974,8 +984,7 @@ maybe_adjust_pc ()
   child_fetch_inferior_registers (regcache, -1);
 
   windows_thread_info *th
-    = windows_process.thread_rec (current_thread_ptid (),
-				  DONT_INVALIDATE_CONTEXT);
+    = windows_process.find_thread (current_thread_ptid ());
   th->stopped_at_software_breakpoint = false;
 
   if (windows_process.current_event.dwDebugEventCode == EXCEPTION_DEBUG_EVENT
@@ -1375,8 +1384,7 @@ win32_process_target::supports_get_tib_address ()
 int
 win32_process_target::get_tib_address (ptid_t ptid, CORE_ADDR *addr)
 {
-  windows_thread_info *th;
-  th = windows_process.thread_rec (ptid, DONT_INVALIDATE_CONTEXT);
+  windows_thread_info *th = windows_process.find_thread (ptid);
   if (th == NULL)
     return 0;
   if (addr != NULL)
@@ -1397,8 +1405,7 @@ bool
 win32_process_target::stopped_by_sw_breakpoint ()
 {
   windows_thread_info *th
-    = windows_process.thread_rec (current_thread_ptid (),
-				  DONT_INVALIDATE_CONTEXT);
+    = windows_process.find_thread (current_thread_ptid ());
   return th == nullptr ? false : th->stopped_at_software_breakpoint;
 }
 
@@ -1424,8 +1431,7 @@ const char *
 win32_process_target::thread_name (ptid_t thread)
 {
   windows_thread_info *th
-    = windows_process.thread_rec (current_thread_ptid (),
-				  DONT_INVALIDATE_CONTEXT);
+    = windows_process.find_thread (current_thread_ptid ());
   return th->thread_name ();
 }
 
diff --git a/gdbserver/win32-low.h b/gdbserver/win32-low.h
index ff997df..c725c18 100644
--- a/gdbserver/win32-low.h
+++ b/gdbserver/win32-low.h
@@ -174,6 +174,7 @@ public:
 
 struct gdbserver_windows_process : public windows_nat::windows_process_info
 {
+  windows_nat::windows_thread_info *find_thread (ptid_t ptid) override;
   windows_nat::windows_thread_info *thread_rec
        (ptid_t ptid,
 	windows_nat::thread_disposition_type disposition) override;