[m-rev.] diff: ThreadScope support improvments.

[Paul Bone]

ThreadScope support improvements.

Provide a new event for context re-use rather than creation.  This event
is true to Mercury's behaviour; the existing threadscope events were
not.

Bring Mercury's usage of the create context event into line with
ThreadScope's expectations.

mercury_threadscope.[ch]:
    Add a new event for when a context is re-used (and it's id is
    re-assigned).  This is like the create context event except that the
    storage came from a previously used context.

mercury_context.c:
    Post the reuse context event when a context is re-used from the
    free list.

    Post reuse context when a context that an engine already has is
    re-used for a stolen spark.  XXX: Check locally allocated contexts.

    A result of these changes is that the create context message is used
    even when a context is created to evaluate sparks.  This is
    deliberate: Some of ThreadScope's analyses require this.

mercury_thread.c:
mercury_context.c:
    Place the create context event in MR_create_context rather than
    after MR_create_context returns.

mercury_par_builtin.h:
    Fixed the order of some type qualifiers.  volatile was incorrectly
    referring to the pointer's target and not the pointer.

Index: runtime/mercury_context.c
===================================================================
RCS file: /home/mercury/mercury1/repository/mercury/runtime/mercury_context.c,v
retrieving revision 1.105
diff -u -r1.105 mercury_context.c
--- runtime/mercury_context.c	24 Nov 2011 12:32:31 -0000	1.105
+++ runtime/mercury_context.c	19 Jun 2012 10:47:02 -0000
@@ -1057,11 +1057,18 @@
     }
     MR_UNLOCK(&free_context_list_lock, "create_context i");
 
+    if (c != NULL) {
+#ifdef MR_THREADSCOPE
+        MR_Unsigned old_id = c->MR_ctxt_num_id;
+
+        c->MR_ctxt_num_id = allocate_context_id();
+        MR_threadscope_post_reuse_context(c, old_id);
+#endif
 #ifdef MR_DEBUG_STACK_SEGMENTS
-    MR_debug_log_message("Re-used an old context: %p", c);
+        MR_debug_log_message("Re-used an old context: %p", c);
 #endif
-
-    if (c == NULL) {
+    }
+    else {
         c = MR_GC_NEW_ATTRIB(MR_Context, MR_ALLOC_SITE_RUNTIME);
 #ifdef MR_DEBUG_STACK_SEGMENTS
         if (c) {
@@ -1078,6 +1085,7 @@
 #endif
 #ifdef MR_THREADSCOPE
         c->MR_ctxt_num_id = allocate_context_id();
+        MR_threadscope_post_create_context(c);
 #endif
     }
 
@@ -2065,6 +2073,15 @@
         MR_debug_log_message("created new context for spark: %p",
             MR_ENGINE(MR_eng_this_context));
 #endif
+    } else {
+#ifdef MR_THREADSCOPE
+        MR_Unsigned old_id;
+
+        old_id = MR_ENGINE(MR_eng_this_context)->MR_ctxt_num_id;
+        MR_ENGINE(MR_eng_this_context)->MR_ctxt_num_id = allocate_context_id();
+        MR_threadscope_post_reuse_context(MR_ENGINE(MR_eng_this_context),
+            old_id);
+#endif
     }
 #ifdef MR_THREADSCOPE
     MR_threadscope_post_run_context();
Index: runtime/mercury_par_builtin.h
===================================================================
RCS file: /home/mercury/mercury1/repository/mercury/runtime/mercury_par_builtin.h,v
retrieving revision 1.16
diff -u -r1.16 mercury_par_builtin.h
--- runtime/mercury_par_builtin.h	20 Oct 2011 04:37:43 -0000	1.16
+++ runtime/mercury_par_builtin.h	19 Jun 2012 10:47:06 -0000
@@ -307,7 +307,7 @@
 
     /* This lock protects only the next field */
     MR_THREADSAFE_VOLATILE MR_Us_Lock       MR_lc_master_context_lock;
-    MR_THREADSAFE_VOLATILE MR_Context       *MR_lc_master_context;
+    MR_Context* MR_THREADSAFE_VOLATILE      MR_lc_master_context;
 
     /* Unused atm */
     MR_THREADSAFE_VOLATILE MR_bool          MR_lc_finished;
Index: runtime/mercury_thread.c
===================================================================
RCS file: /home/mercury/mercury1/repository/mercury/runtime/mercury_thread.c,v
retrieving revision 1.51
diff -u -r1.51 mercury_thread.c
--- runtime/mercury_thread.c	28 Nov 2011 05:14:26 -0000	1.51
+++ runtime/mercury_thread.c	19 Jun 2012 10:47:10 -0000
@@ -213,9 +213,6 @@
                 MR_ENGINE(MR_eng_this_context) =
                     MR_create_context("init_thread",
                         MR_CONTEXT_SIZE_REGULAR, NULL);
-#ifdef MR_THREADSCOPE
-                MR_threadscope_post_create_context(MR_ENGINE(MR_eng_this_context));
-#endif
             }
             MR_load_context(MR_ENGINE(MR_eng_this_context));
 #ifdef MR_THREADSCOPE
Index: runtime/mercury_threadscope.c
===================================================================
RCS file: /home/mercury/mercury1/repository/mercury/runtime/mercury_threadscope.c,v
retrieving revision 1.19
diff -u -r1.19 mercury_threadscope.c
--- runtime/mercury_threadscope.c	16 Jun 2012 06:30:57 -0000	1.19
+++ runtime/mercury_threadscope.c	19 Jun 2012 10:47:10 -0000
@@ -212,7 +212,8 @@
 #define MR_TS_MER_EVENT_CALLING_MAIN        113 /* () */
 #define MR_TS_MER_EVENT_SPARK_RUN           114 /* (spark id) */
 #define MR_TS_MER_EVENT_SPARK_STEAL         115 /* (victim cap, spark id) */
-#define MR_TS_NUM_MER_EVENTS                 16
+#define MR_TS_MER_EVENT_REUSE_THREAD        116 /* (context id, old context id) */
+#define MR_TS_NUM_MER_EVENTS                 17
 
 #if 0  /* DEPRECATED EVENTS: */
 #define EVENT_CREATE_SPARK        13 /* (cap, thread) */
@@ -638,6 +639,16 @@
         0xFFFF
     },
     {
+        /*
+        ** The runtime system is re-useing a previous context and
+        ** re-assigning its ID.
+        */
+        MR_TS_MER_EVENT_REUSE_THREAD,
+        "Reusing a previously allocated thread",
+        SZ_CONTEXT_ID + SZ_CONTEXT_ID,
+        MR_TS_EVENT_CREATE_THREAD
+    },
+    {
         /* Mark the end of this array. */
         MR_TS_NUM_EVENT_TAGS,
         NULL,
@@ -1259,6 +1270,28 @@
 }
 
 void
+MR_threadscope_post_reuse_context(MR_Context *context, MR_Unsigned old_id)
+{
+    struct MR_threadscope_event_buffer *buffer = MR_ENGINE(MR_eng_ts_buffer);
+
+    MR_US_SPIN_LOCK(&(buffer->MR_tsbuffer_lock));
+
+    if (!enough_room_for_event(buffer, MR_TS_MER_EVENT_REUSE_THREAD)) {
+        flush_event_buffer(buffer);
+        open_block(buffer, MR_ENGINE(MR_eng_id));
+    } else if (!block_is_open(buffer)) {
+        open_block(buffer, MR_ENGINE(MR_eng_id));
+    }
+
+    put_event_header(buffer, MR_TS_MER_EVENT_REUSE_THREAD,
+        get_current_time_nanosecs());
+    put_context_id(buffer, context->MR_ctxt_num_id);
+    put_context_id(buffer, old_id);
+
+    MR_US_UNLOCK(&(buffer->MR_tsbuffer_lock));
+}
+
+void
 MR_threadscope_post_create_context_for_spark(MR_Context *context)
 {
     struct MR_threadscope_event_buffer *buffer = MR_ENGINE(MR_eng_ts_buffer);
Index: runtime/mercury_threadscope.h
===================================================================
RCS file: /home/mercury/mercury1/repository/mercury/runtime/mercury_threadscope.h,v
retrieving revision 1.14
diff -u -r1.14 mercury_threadscope.h
--- runtime/mercury_threadscope.h	8 Sep 2011 01:53:08 -0000	1.14
+++ runtime/mercury_threadscope.h	19 Jun 2012 10:47:10 -0000
@@ -98,8 +98,9 @@
                 struct MR_Context_Struct *context);
 
 /*
-** The given context was created in order to execute a spark.  It's an
-** alternative to the above event.
+** The given context was created in order to execute a spark.  This
+** event should be posted in addition to (and after) create_thread
+** above.
 */
 extern void MR_threadscope_post_create_context_for_spark(
                 struct MR_Context_Struct *ctxt);
@@ -113,6 +114,13 @@
                 struct MR_Context_Struct *context);
 
 /*
+** This context is being reused (after being released). This event is an
+** alternative to create_context above.
+*/
+extern void MR_threadscope_post_reuse_context(
+                struct MR_Context_Struct *context, MR_Unsigned old_id);
+
+/*
 ** This message says the context is now ready to run.  Such as it's being
 ** placed on the run queue after being blocked
 */
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