pkg/corpus: don't overwrite ProgsList

There's still a risk of a race between the pointer overwriting and
accesses to the embedded object.

Let's use an internal replace() method instead.

2 files changed, 23 insertions, 16 deletions

diff --git a/pkg/corpus/minimize.go b/pkg/corpus/minimize.go
index 938bd1d2e..b23f9f29e 100644
--- a/pkg/corpus/minimize.go
+++ b/pkg/corpus/minimize.go
@@ -32,12 +32,11 @@ func (corpus *Corpus) Minimize(cover bool) {
 	})
 
 	corpus.progs = make(map[string]*Item)
-	// ProgramsList has its own mutex, so it'd be unsafe to
-	// overwrite it here, so let's create a new object.
-	corpus.ProgramsList = &ProgramsList{}
+	programsList := &ProgramsList{}
 	for _, ctx := range signal.Minimize(inputs) {
 		inp := ctx.(*Item)
 		corpus.progs[inp.Sig] = inp
-		corpus.saveProgram(inp.Prog, inp.Signal)
+		programsList.saveProgram(inp.Prog, inp.Signal)
 	}
+	corpus.ProgramsList.replace(programsList)
 }
diff --git a/pkg/corpus/prio.go b/pkg/corpus/prio.go
index a4d85a518..57f9ddaf5 100644
--- a/pkg/corpus/prio.go
+++ b/pkg/corpus/prio.go
@@ -19,18 +19,6 @@ type ProgramsList struct {
 	accPrios []int64
 }
 
-func (pl *ProgramsList) saveProgram(p *prog.Prog, signal signal.Signal) {
-	pl.mu.Lock()
-	defer pl.mu.Unlock()
-	prio := int64(len(signal))
-	if prio == 0 {
-		prio = 1
-	}
-	pl.sumPrios += prio
-	pl.accPrios = append(pl.accPrios, pl.sumPrios)
-	pl.progs = append(pl.progs, p)
-}
-
 func (pl *ProgramsList) ChooseProgram(r *rand.Rand) *prog.Prog {
 	pl.mu.RLock()
 	defer pl.mu.RUnlock()
@@ -49,3 +37,23 @@ func (pl *ProgramsList) Programs() []*prog.Prog {
 	defer pl.mu.RUnlock()
 	return pl.progs
 }
+
+func (pl *ProgramsList) saveProgram(p *prog.Prog, signal signal.Signal) {
+	pl.mu.Lock()
+	defer pl.mu.Unlock()
+	prio := int64(len(signal))
+	if prio == 0 {
+		prio = 1
+	}
+	pl.sumPrios += prio
+	pl.accPrios = append(pl.accPrios, pl.sumPrios)
+	pl.progs = append(pl.progs, p)
+}
+
+func (pl *ProgramsList) replace(other *ProgramsList) {
+	pl.mu.Lock()
+	defer pl.mu.Unlock()
+	pl.sumPrios = other.sumPrios
+	pl.accPrios = other.accPrios
+	pl.progs = other.progs
+}