syz-fuzzer: fix manager polling

We need to always poll manager to send stats/maxsignal,
we just need not request candidates if we have plenty of work.

pkg/rpctype/rpctype.go

@@ -51,9 +51,10 @@ type NewInputArgs struct {
 }
 
 type PollArgs struct {
-	Name      string
-	MaxSignal []uint32
-	Stats     map[string]uint64
+	Name           string
+	NeedCandidates bool
+	MaxSignal      []uint32
+	Stats          map[string]uint64
 }
 
 type PollRes struct {

syz-fuzzer/fuzzer.go

@@ -346,15 +346,16 @@ func main() {
 		}
 		if poll || time.Since(lastPoll) > 10*time.Second {
 			triageMu.RLock()
-			if len(candidates) > *flagProcs {
-				triageMu.RUnlock()
+			needCandidates := len(candidates) < *flagProcs
+			triageMu.RUnlock()
+			if !needCandidates && poll {
 				continue
 			}
-			triageMu.RUnlock()
 
 			a := &PollArgs{
-				Name:  *flagName,
-				Stats: make(map[string]uint64),
+				Name:           *flagName,
+				NeedCandidates: needCandidates,
+				Stats:          make(map[string]uint64),
 			}
 			signalMu.Lock()
 			a.MaxSignal = make([]uint32, 0, len(newSignal))
@@ -390,6 +391,8 @@ func main() {
 			if err := manager.Call("Manager.Poll", a, r); err != nil {
 				panic(err)
 			}
+			Logf(1, "poll: candidates=%v inputs=%v signal=%v",
+				len(r.Candidates), len(r.NewInputs), len(r.MaxSignal))
 			if len(r.MaxSignal) != 0 {
 				signalMu.Lock()
 				for _, s := range r.MaxSignal {

syz-manager/manager.go

@@ -996,10 +996,12 @@ func (mgr *Manager) Poll(a *PollArgs, r *PollRes) error {
 		f.inputs = nil
 	}
 
-	for i := 0; i < mgr.cfg.Procs && len(mgr.candidates) > 0; i++ {
-		last := len(mgr.candidates) - 1
-		r.Candidates = append(r.Candidates, mgr.candidates[last])
-		mgr.candidates = mgr.candidates[:last]
+	if a.NeedCandidates {
+		for i := 0; i < mgr.cfg.Procs && len(mgr.candidates) > 0; i++ {
+			last := len(mgr.candidates) - 1
+			r.Candidates = append(r.Candidates, mgr.candidates[last])
+			mgr.candidates = mgr.candidates[:last]
+		}
 	}
 	if len(mgr.candidates) == 0 {
 		mgr.candidates = nil