Emit the task-tracking events

Based on initial patches by Mikolaj Konarski <mikolaj@well-typed.com>

Use the new task tracing functions traceTaskCreate/Migrate/Delete.
There are two key places. One is for worker tasks which have a
relatively simple life cycle. Worker tasks are created and deleted by
the RTS. The other case is bound tasks which are either created by the
RTS, or appear as foreign C threads making calls into the RTS. For bound
threads we do the tracing in rts_lock/unlock, which actually covers both
threads coming in from outside, and also bound threads made by the RTS.

1 files changed, 12 insertions, 0 deletions

diff --git a/rts/Task.c b/rts/Task.c
index b6092e5e41..6c814886ba 100644
--- a/rts/Task.c
+++ b/rts/Task.c
@@ -321,6 +321,11 @@ discardTasksExcept (Task *keep)
         next = task->all_next;
         if (task != keep) {
             debugTrace(DEBUG_sched, "discarding task %" FMT_SizeT "", (size_t)TASK_ID(task));
+            // Note that we do not traceTaskDelete here because
+            // we are not really deleting a task.
+            // The OS threads for all these tasks do not exist in
+            // this process (since we're currently
+            // in the child of a forkProcess).
             freeTask(task);
         }
     }
@@ -383,6 +388,8 @@ workerTaskStop (Task *task)
 
     RELEASE_LOCK(&all_tasks_mutex);
 
+    traceTaskDelete(task);
+
     freeTask(task);
 }
 
@@ -425,6 +432,9 @@ workerStart(Task *task)
 
     newInCall(task);
 
+    // Everything set up; emit the event before the worker starts working.
+    traceTaskCreate(task, cap);
+
     scheduleWorker(cap,task);
 }
 
@@ -443,6 +453,8 @@ startWorkerTask (Capability *cap)
   // worker thread reads it.
   ACQUIRE_LOCK(&task->lock);
 
+  // We don't emit a task creation event here, but in workerStart,
+  // where the kernel thread id is known.
   task->cap = cap;
 
   // Give the capability directly to the worker; we can't let anyone