[PATCH v2 10/17] btrace: temporarily set inferior_ptid in record_btrace_start_replaying

[Markus Metzger <markus dot t dot metzger at intel dot com>]

Get_current_frame uses inferior_ptid.  In record_btrace_start_replaying,
we need to get the current frame of the argument thread.  So far, this
has always been inferior_ptid.  With non-stop, this is not guaranteed.

Temporarily set inferior_ptid to the ptid of the argument thread.

We already temporarily set the argument thread's executing flag to false.

Move both into a new function get_thread_current_frame that does the temporary
adjustments, calls get_current_frame, and restores the previous values.

2015-09-11  Markus Metzger <markus.t.metzger@intel.com>

gdb/
	* record-btrace.c (get_thread_current_frame): New.
	(record_btrace_start_replaying): Call get_thread_current_frame.
---
 gdb/record-btrace.c | 70 ++++++++++++++++++++++++++++++++++++++---------------
 1 file changed, 51 insertions(+), 19 deletions(-)

diff --git a/gdb/record-btrace.c b/gdb/record-btrace.c
index c25b8f4..0514471 100644
--- a/gdb/record-btrace.c
+++ b/gdb/record-btrace.c
@@ -1707,6 +1707,55 @@ record_btrace_resume_thread (struct thread_info *tp,
   btinfo->flags |= flag;
 }
 
+/* Get the current frame for TP.  */
+
+static struct frame_info *
+get_thread_current_frame (struct thread_info *tp)
+{
+  struct frame_info *frame;
+  ptid_t old_inferior_ptid;
+  int executing;
+
+  /* Set INFERIOR_PTID, which is implicitly used by get_current_frame.  */
+  old_inferior_ptid = inferior_ptid;
+  inferior_ptid = tp->ptid;
+
+  /* Clear the executing flag to allow changes to the current frame.
+     We are not actually running, yet.  We just started a reverse execution
+     command or a record goto command.
+     For the latter, EXECUTING is false and this has no effect.
+     For the former, EXECUTING is true and we're in to_wait, about to
+     move the thread.  Since we need to recompute the stack, we temporarily
+     set EXECUTING to flase.  */
+  executing = is_executing (inferior_ptid);
+  set_executing (inferior_ptid, 0);
+
+  frame = NULL;
+  TRY
+    {
+      frame = get_current_frame ();
+    }
+  CATCH (except, RETURN_MASK_ALL)
+    {
+      /* Restore the previous execution state.  */
+      set_executing (inferior_ptid, executing);
+
+      /* Restore the previous inferior_ptid.  */
+      inferior_ptid = old_inferior_ptid;
+
+      throw_exception (except);
+    }
+  END_CATCH
+
+  /* Restore the previous execution state.  */
+  set_executing (inferior_ptid, executing);
+
+  /* Restore the previous inferior_ptid.  */
+  inferior_ptid = old_inferior_ptid;
+
+  return frame;
+}
+
 /* Start replaying a thread.  */
 
 static struct btrace_insn_iterator *
@@ -1714,7 +1763,6 @@ record_btrace_start_replaying (struct thread_info *tp)
 {
   struct btrace_insn_iterator *replay;
   struct btrace_thread_info *btinfo;
-  int executing;
 
   btinfo = &tp->btrace;
   replay = NULL;
@@ -1723,16 +1771,6 @@ record_btrace_start_replaying (struct thread_info *tp)
   if (btinfo->begin == NULL)
     return NULL;
 
-  /* Clear the executing flag to allow changes to the current frame.
-     We are not actually running, yet.  We just started a reverse execution
-     command or a record goto command.
-     For the latter, EXECUTING is false and this has no effect.
-     For the former, EXECUTING is true and we're in to_wait, about to
-     move the thread.  Since we need to recompute the stack, we temporarily
-     set EXECUTING to flase.  */
-  executing = is_executing (tp->ptid);
-  set_executing (tp->ptid, 0);
-
   /* GDB stores the current frame_id when stepping in order to detects steps
      into subroutines.
      Since frames are computed differently when we're replaying, we need to
@@ -1745,7 +1783,7 @@ record_btrace_start_replaying (struct thread_info *tp)
       int upd_step_frame_id, upd_step_stack_frame_id;
 
       /* The current frame without replaying - computed via normal unwind.  */
-      frame = get_current_frame ();
+      frame = get_thread_current_frame (tp);
       frame_id = get_frame_id (frame);
 
       /* Check if we need to update any stepping-related frame id's.  */
@@ -1777,7 +1815,7 @@ record_btrace_start_replaying (struct thread_info *tp)
       registers_changed_ptid (tp->ptid);
 
       /* The current frame with replaying - computed via btrace unwind.  */
-      frame = get_current_frame ();
+      frame = get_thread_current_frame (tp);
       frame_id = get_frame_id (frame);
 
       /* Replace stepping related frames where necessary.  */
@@ -1788,9 +1826,6 @@ record_btrace_start_replaying (struct thread_info *tp)
     }
   CATCH (except, RETURN_MASK_ALL)
     {
-      /* Restore the previous execution state.  */
-      set_executing (tp->ptid, executing);
-
       xfree (btinfo->replay);
       btinfo->replay = NULL;
 
@@ -1800,9 +1835,6 @@ record_btrace_start_replaying (struct thread_info *tp)
     }
   END_CATCH
 
-  /* Restore the previous execution state.  */
-  set_executing (tp->ptid, executing);
-
   return replay;
 }
 
-- 
1.8.3.1