rts: Flush eventlog buffers from flushEventLogwip/T18043

As noted in #18043, flushTrace failed flush anything beyond the writer.
This means that a significant amount of data sitting in capability-local
event buffers may never get flushed, despite the users' pleads for us to
flush.

Fix this by making flushEventLog flush all of the event buffers before
flushing the writer.

Fixes #18043.

2 files changed, 46 insertions, 4 deletions

diff --git a/rts/eventlog/EventLog.c b/rts/eventlog/EventLog.c
index 11e8a5e0b6..bce2fa493f 100644
--- a/rts/eventlog/EventLog.c
+++ b/rts/eventlog/EventLog.c
@@ -16,6 +16,7 @@
 #include "RtsUtils.h"
 #include "Stats.h"
 #include "EventLog.h"
+#include "Schedule.h"
 
 #include <string.h>
 #include <stdio.h>
@@ -270,8 +271,8 @@ stopEventLogWriter(void)
     }
 }
 
-void
-flushEventLog(void)
+static void
+flushEventLogWriter(void)
 {
     if (event_log_writer != NULL &&
             event_log_writer->flushEventLog != NULL) {
@@ -1484,7 +1485,7 @@ void printAndClearEventBuf (EventsBuf *ebuf)
                     "printAndClearEventLog: could not flush event log\n"
                 );
             resetEventsBuf(ebuf);
-            flushEventLog();
+            flushEventLogWriter();
             return;
         }
 
@@ -1566,6 +1567,40 @@ void postEventType(EventsBuf *eb, EventType *et)
     postInt32(eb, EVENT_ET_END);
 }
 
+void flushLocalEventsBuf(Capability *cap)
+{
+    EventsBuf *eb = &capEventBuf[cap->no];
+    printAndClearEventBuf(eb);
+}
+
+// Flush all capabilities' event buffers when we already hold all capabilities.
+// Used during forkProcess.
+void flushAllCapsEventsBufs()
+{
+    ACQUIRE_LOCK(&eventBufMutex);
+    printAndClearEventBuf(&eventBuf);
+    RELEASE_LOCK(&eventBufMutex);
+
+    for (unsigned int i=0; i < n_capabilities; i++) {
+        flushLocalEventsBuf(capabilities[i]);
+    }
+    flushEventLogWriter();
+}
+
+void flushEventLog(Capability **cap USED_IF_THREADS)
+{
+    ACQUIRE_LOCK(&eventBufMutex);
+    printAndClearEventBuf(&eventBuf);
+    RELEASE_LOCK(&eventBufMutex);
+
+#if defined(THREADED_RTS)
+    Task *task = getMyTask();
+    stopAllCapabilitiesWith(cap, task, SYNC_FLUSH_EVENT_LOG);
+    releaseAllCapabilities(n_capabilities, cap ? *cap : NULL, task);
+#endif
+    flushEventLogWriter();
+}
+
 #else
 
 enum EventLogStatus eventLogStatus(void)
@@ -1579,4 +1614,6 @@ bool startEventLogging(const EventLogWriter *writer STG_UNUSED) {
 
 void endEventLogging(void) {}
 
+void flushEventLog(Capability **cap STG_UNUSED) {}
+
 #endif /* TRACING */
diff --git a/rts/eventlog/EventLog.h b/rts/eventlog/EventLog.h
index eca76619cd..04ed1982a3 100644
--- a/rts/eventlog/EventLog.h
+++ b/rts/eventlog/EventLog.h
@@ -28,8 +28,10 @@ void initEventLogging(void);
 void restartEventLogging(void);
 void freeEventLogging(void);
 void abortEventLogging(void); // #4512 - after fork child needs to abort
-void flushEventLog(void);     // event log inherited from parent
 void moreCapEventBufs (uint32_t from, uint32_t to);
+void flushLocalEventsBuf(Capability *cap);
+void flushAllCapsEventsBufs(void);
+void flushAllEventsBufs(Capability *cap);
 
 /*
  * Post a scheduler event to the capability's event buffer (an event
@@ -175,6 +177,9 @@ void postNonmovingHeapCensus(int log_blk_size,
 
 #else /* !TRACING */
 
+INLINE_HEADER void flushLocalEventsBuf(Capability *cap STG_UNUSED)
+{ /* nothing */ }
+
 INLINE_HEADER void postSchedEvent (Capability *cap  STG_UNUSED,
                                    EventTypeNum tag STG_UNUSED,
                                    StgThreadID id   STG_UNUSED,