Add eventlog/trace stuff for capabilities: create/delete/enable/disable

Now that we can adjust the number of capabilities on the fly, we need
this reflected in the eventlog. Previously the eventlog had a single
startup event that declared a static number of capabilities. Obviously
that's no good anymore.

For compatability we're keeping the EVENT_STARTUP but adding new
EVENT_CAP_CREATE/DELETE. The EVENT_CAP_DELETE is actually just the old
EVENT_SHUTDOWN but renamed and extended (using the existing mechanism
to extend eventlog events in a compatible way). So we now emit both
EVENT_STARTUP and EVENT_CAP_CREATE. One day we will drop EVENT_STARTUP.

Since reducing the number of capabilities at runtime does not really
delete them, it just disables them, then we also have new events for
disable/enable.

The old EVENT_SHUTDOWN was in the scheduler class of events. The new
EVENT_CAP_* events are in the unconditional class, along with the
EVENT_CAPSET_* ones. Knowing when capabilities are created and deleted
is crucial to making sense of eventlogs, you always want those events.
In any case, they're extremely low volume.

2 files changed, 46 insertions, 9 deletions

diff --git a/rts/eventlog/EventLog.c b/rts/eventlog/EventLog.c
index af87492876..8009a38938 100644
--- a/rts/eventlog/EventLog.c
+++ b/rts/eventlog/EventLog.c
@@ -60,9 +60,13 @@ char *EventDesc[] = {
   [EVENT_STOP_THREAD]         = "Stop thread",
   [EVENT_THREAD_RUNNABLE]     = "Thread runnable",
   [EVENT_MIGRATE_THREAD]      = "Migrate thread",
-  [EVENT_SHUTDOWN]            = "Shutdown",
   [EVENT_THREAD_WAKEUP]       = "Wakeup thread",
   [EVENT_THREAD_LABEL]        = "Thread label",
+  [EVENT_STARTUP]             = "Create capabilities",
+  [EVENT_CAP_CREATE]          = "Create capability",
+  [EVENT_CAP_DELETE]          = "Delete capability",
+  [EVENT_CAP_DISABLE]         = "Disable capability",
+  [EVENT_CAP_ENABLE]          = "Enable capability",
   [EVENT_GC_START]            = "Starting GC",
   [EVENT_GC_END]              = "Finished GC",
   [EVENT_REQUEST_SEQ_GC]      = "Request sequential GC",
@@ -70,7 +74,6 @@ char *EventDesc[] = {
   [EVENT_CREATE_SPARK_THREAD] = "Create spark thread",
   [EVENT_LOG_MSG]             = "Log message",
   [EVENT_USER_MSG]            = "User message",
-  [EVENT_STARTUP]             = "Startup",
   [EVENT_GC_IDLE]             = "GC idle",
   [EVENT_GC_WORK]             = "GC working",
   [EVENT_GC_DONE]             = "GC done",
@@ -287,7 +290,11 @@ initEventLogging(void)
                 sizeof(EventThreadID) + sizeof(StgWord16) + sizeof(EventThreadID);
             break;
 
-        case EVENT_STARTUP:         // (cap count)
+        case EVENT_STARTUP:         // (cap_count)
+        case EVENT_CAP_CREATE:      // (cap)
+        case EVENT_CAP_DELETE:      // (cap)
+        case EVENT_CAP_ENABLE:      // (cap)
+        case EVENT_CAP_DISABLE:     // (cap)
             eventTypes[t].size = sizeof(EventCapNo);
             break;
 
@@ -322,7 +329,6 @@ initEventLogging(void)
                 sizeof(EventCapNo);
             break;
 
-        case EVENT_SHUTDOWN:        // (cap)
         case EVENT_REQUEST_SEQ_GC:  // (cap)
         case EVENT_REQUEST_PAR_GC:  // (cap)
         case EVENT_GC_START:        // (cap)
@@ -519,11 +525,6 @@ postSchedEvent (Capability *cap,
         break;
     }
 
-    case EVENT_SHUTDOWN:        // (cap)
-    {
-        break;
-    }
-
     default:
         barf("postSchedEvent: unknown event tag %d", tag);
     }
@@ -597,6 +598,36 @@ postSparkCountersEvent (Capability *cap,
     postWord64(eb,remaining);
 }
 
+void
+postCapEvent (EventTypeNum  tag,
+              EventCapNo    capno)
+{
+    ACQUIRE_LOCK(&eventBufMutex);
+
+    if (!hasRoomForEvent(&eventBuf, tag)) {
+        // Flush event buffer to make room for new event.
+        printAndClearEventBuf(&eventBuf);
+    }
+    
+    postEventHeader(&eventBuf, tag);
+
+    switch (tag) {
+    case EVENT_CAP_CREATE:   // (cap)
+    case EVENT_CAP_DELETE:   // (cap)
+    case EVENT_CAP_ENABLE:   // (cap)
+    case EVENT_CAP_DISABLE:  // (cap)
+    {
+        postCapNo(&eventBuf,capno);
+        break;
+    }
+
+    default:
+        barf("postCapEvent: unknown event tag %d", tag);
+    }
+
+    RELEASE_LOCK(&eventBufMutex);
+}
+
 void postCapsetEvent (EventTypeNum tag,
                       EventCapsetID capset,
                       StgWord info)
diff --git a/rts/eventlog/EventLog.h b/rts/eventlog/EventLog.h
index 1858be8ecd..6a3b32dad3 100644
--- a/rts/eventlog/EventLog.h
+++ b/rts/eventlog/EventLog.h
@@ -49,6 +49,12 @@ void postCapMsg(Capability *cap, char *msg, va_list ap);
 void postEventStartup(EventCapNo n_caps);
 
 /*
+ * Post an event relating to a capability itself (create/delete/etc)
+ */
+void postCapEvent (EventTypeNum  tag,
+                   EventCapNo    capno);
+
+/*
  * Post an event that is associated with a capability set
  */
 void postCapsetEvent (EventTypeNum tag,