From 9cbf9ec8e9eac92431b9a742c1b625888cb69dfa Mon Sep 17 00:00:00 2001
From: Paul Buetow <paul@buetow.org>
Date: Sun, 8 Mar 2026 11:24:31 +0200
Subject: eventloop: remove gosched by snapshotting emitted fd state

---
 internal/eventloop.go      | 13 +++++++++----
 internal/eventloop_test.go | 25 +++++++++++++++++++++++++
 2 files changed, 34 insertions(+), 4 deletions(-)

diff --git a/internal/eventloop.go b/internal/eventloop.go
index 64c7d6f..2c3cf49 100644
--- a/internal/eventloop.go
+++ b/internal/eventloop.go
@@ -8,7 +8,6 @@ import (
 	"os"
 	"path/filepath"
 	"reflect"
-	"runtime"
 	"sync"
 	"syscall"
 	"time"
@@ -408,9 +407,6 @@ func (e *eventLoop) events(ctx context.Context, rawCh <-chan []byte) <-chan *eve
 					continue
 				}
 				e.processRawEvent(raw, ch)
-				// Yield so downstream consumers can process emitted pairs before
-				// the next raw event mutates shared tracker state.
-				runtime.Gosched()
 			case <-ctx.Done():
 				fmt.Println("Stopping event loop")
 				return
@@ -593,9 +589,18 @@ func (e *eventLoop) tracepointExited(exitEv event.Event, ch chan<- *event.Pair)
 	prevPairTime, _ := e.prevPairTimes[ep.EnterEv.GetTid()]
 	ep.CalculateDurations(prevPairTime)
 	e.prevPairTimes[ep.EnterEv.GetTid()] = ep.ExitEv.GetTime()
+	e.freezePairForEmission(ep)
 	ch <- ep
 }
 
+func (e *eventLoop) freezePairForEmission(ep *event.Pair) {
+	fdFile, ok := ep.File.(*file.FdFile)
+	if !ok {
+		return
+	}
+	ep.File = fdFile.Dup(fdFile.FD())
+}
+
 func (e *eventLoop) initExitHandlers() {
 	e.exitHandlers = map[reflect.Type]tracepointExitHandler{
 		reflect.TypeOf(&types.OpenEvent{}): func(ep *event.Pair) bool {
diff --git a/internal/eventloop_test.go b/internal/eventloop_test.go
index 32dddd4..3a4ad38 100644
--- a/internal/eventloop_test.go
+++ b/internal/eventloop_test.go
@@ -203,6 +203,31 @@ func TestHandleFdExitCloseRangeClearsProcFdCacheRange(t *testing.T) {
 	verifyProcFdCached(t, el, pid+1, 20)
 }
 
+func TestFreezePairForEmissionCopiesFdFile(t *testing.T) {
+	el := mustNewEventLoop(t, eventLoopConfig{})
+	fdFile := file.NewFd(9, "/tmp/x", syscall.O_RDONLY)
+	ep := event.NewPair(&types.NullEvent{})
+	ep.File = fdFile
+
+	el.freezePairForEmission(ep)
+
+	emitted, ok := ep.File.(*file.FdFile)
+	if !ok {
+		t.Fatalf("expected emitted file to be *file.FdFile, got %T", ep.File)
+	}
+	if emitted == fdFile {
+		t.Fatalf("expected emitted fd file to be detached copy")
+	}
+	if emitted.Flags() != file.Flags(syscall.O_RDONLY) {
+		t.Fatalf("expected copied flags %v, got %v", syscall.O_RDONLY, emitted.Flags())
+	}
+
+	fdFile.SetFlags(syscall.O_WRONLY)
+	if emitted.Flags() != file.Flags(syscall.O_RDONLY) {
+		t.Fatalf("expected emitted copy flags unchanged after source mutation")
+	}
+}
+
 // Tests a simple enter/exit pair of tracepoints.
 func makeOpenEventTestData1(t *testing.T) (td testData) {
 	enterEv, enterEvBytes := makeEnterOpenEvent(t, defaulTime, defaultPid, defaultTid)
-- 
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