pkg/manager: improve error accounting during diff fuzzing

When running the reproducer from the patched kernel on the base kernel,
stay on the safe side when encountering errors and context
cancellations.

Always demand 3 successful executions before declaring a bug
patched-only.

Author: a-nogikh

pkg/manager/diff.go

@@ -585,15 +585,21 @@ func (rr *reproRunner) Run(ctx context.Context, r *repro.Result) {
 	ret := reproRunnerResult{origReport: r.Report, repro: r}
 
 	var result *instance.RunResult
-	var err error
-	for i := 0; i < 3; i++ {
+	var doneRuns int
+
+	for doneRuns < 3 {
+		if ctx.Err() != nil {
+			return
+		}
+
 		opts := r.Opts
 		opts.Repeat = true
-		if i == 0 || i == 1 {
+		if doneRuns < 2 {
 			// Two times out of 3, test with Threaded=true.
 			// The third time we leave it as is in case it was important.
 			opts.Threaded = true
 		}
+		var err error
 		runErr := pool.Run(ctx, func(ctx context.Context, inst *vm.Instance, updInfo dispatcher.UpdateInfo) {
 			var ret *instance.ExecProgInstance
 			ret, err = instance.SetupExecProg(inst, rr.kernel.cfg, rr.kernel.reporter, nil)
@@ -606,20 +612,24 @@ func (rr *reproRunner) Run(ctx context.Context, r *repro.Result) {
 				Opts:     opts,
 			})
 		})
+		logPrefix := fmt.Sprintf("attempt #%d to run %q on base", doneRuns, ret.origReport.Title)
 		if errors.Is(runErr, context.Canceled) {
-			break
+			// Just exit without returning anything on the channel.
+			log.Logf(1, "%s: aborting due to context cancelation", logPrefix)
+			return
+		} else if runErr != nil || err != nil {
+			log.Logf(1, "%s: skipping due to errors: %v / %v", logPrefix, runErr, err)
+			continue
 		}
-		crashed := result != nil && result.Report != nil
-		log.Logf(1, "attempt #%d to run %q on base: crashed=%v", i, ret.origReport.Title, crashed)
-		if crashed {
+		doneRuns++
+		if result != nil && result.Report != nil {
+			log.Logf(1, "%s: crashed with %s", logPrefix, result.Report.Title)
 			ret.crashReport = result.Report
 			break
+		} else {
+			log.Logf(1, "%s: did not crash", logPrefix)
 		}
 	}
-	if err != nil {
-		log.Errorf("failed to run repro: %v", err)
-		return
-	}
 	select {
 	case rr.done <- ret:
 	case <-ctx.Done():