Detect deadlock in model and panic

model/model.go

@@ -15,6 +15,7 @@ import (
 	"path/filepath"
 	"sync"
 	"time"
+
 	"github.com/calmh/syncthing/cid"
 	"github.com/calmh/syncthing/config"
 	"github.com/calmh/syncthing/files"
@@ -96,6 +97,9 @@ func NewModel(indexDir string, cfg *config.Configuration, clientName, clientVers
 		sup:           suppressor{threshold: int64(cfg.Options.MaxChangeKbps)},
 	}
 
+	deadlockDetect(&m.rmut, 60*time.Second)
+	deadlockDetect(&m.smut, 60*time.Second)
+	deadlockDetect(&m.pmut, 60*time.Second)
 	go m.broadcastIndexLoop()
 	return m
 }

model/util.go

@@ -7,6 +7,8 @@ package model
 import (
 	"fmt"
 	"path/filepath"
+	"sync"
+	"time"
 
 	"github.com/calmh/syncthing/protocol"
 	"github.com/calmh/syncthing/scanner"
@@ -90,3 +92,27 @@ func compareClusterConfig(local, remote protocol.ClusterConfigMessage) error {
 
 	return nil
 }
+
+func deadlockDetect(mut sync.Locker, timeout time.Duration) {
+	go func() {
+		for {
+			time.Sleep(timeout / 4)
+			ok := make(chan bool, 2)
+
+			go func() {
+				mut.Lock()
+				mut.Unlock()
+				ok <- true
+			}()
+
+			go func() {
+				time.Sleep(timeout)
+				ok <- false
+			}()
+
+			if r := <-ok; !r {
+				panic("deadlock detected")
+			}
+		}
+	}()
+}