@@ -747,6 +747,9 @@ func NewDaemon(config *Config, registryService *registry.Service) (daemon *Daemo

 		return nil, err

 	}

+	// set up SIGUSR1 handler to dump Go routine stacks

+	setupSigusr1Trap()

+

 	// set up the tmpDir to use a canonical path

 	tmp, err := tempDir(config.Root)

 	if err != nil {

new file mode 100644

@@ -0,0 +1,21 @@

+// +build !windows

+

+package daemon

+

+import (

+	"os"

+	"os/signal"

+	"syscall"

+

+	psignal "github.com/docker/docker/pkg/signal"

+)

+

+func setupSigusr1Trap() {

+	c := make(chan os.Signal, 1)

+	signal.Notify(c, syscall.SIGUSR1)

+	go func() {

+		for range c {

+			psignal.DumpStacks()

+		}

+	}()

+}

new file mode 100644

@@ -0,0 +1,7 @@

+// +build !linux,!darwin,!freebsd

+

+package signal

+

+func setupSigusr1Trap() {

+	return

+}

@@ -3,6 +3,7 @@ package signal

 import (

 	"os"

 	gosignal "os/signal"

+	"runtime"

 	"sync/atomic"

 	"syscall"

@@ -14,41 +15,50 @@ import (

 // (and the Docker engine in particular).

 //

 // * If SIGINT or SIGTERM are received, `cleanup` is called, then the process is terminated.

-// * If SIGINT or SIGTERM are repeated 3 times before cleanup is complete, then cleanup is

-// skipped and the process terminated directly.

-// * If "DEBUG" is set in the environment, SIGQUIT causes an exit without cleanup.

+// * If SIGINT or SIGTERM are received 3 times before cleanup is complete, then cleanup is

+//   skipped and the process is terminated immediately (allows force quit of stuck daemon)

+// * A SIGQUIT always causes an exit without cleanup, with a goroutine dump preceding exit.

 //

 func Trap(cleanup func()) {

 	c := make(chan os.Signal, 1)

-	signals := []os.Signal{os.Interrupt, syscall.SIGTERM}

-	if os.Getenv("DEBUG") == "" {

-		signals = append(signals, syscall.SIGQUIT)

-	}

+	// we will handle INT, TERM, QUIT here

+	signals := []os.Signal{os.Interrupt, syscall.SIGTERM, syscall.SIGQUIT}

 	gosignal.Notify(c, signals...)

 	go func() {

 		interruptCount := uint32(0)

 		for sig := range c {

 			go func(sig os.Signal) {

-				logrus.Infof("Received signal '%v', starting shutdown of docker...", sig)

+				logrus.Infof("Processing signal '%v'", sig)

 				switch sig {

 				case os.Interrupt, syscall.SIGTERM:

-					// If the user really wants to interrupt, let him do so.

 					if atomic.LoadUint32(&interruptCount) < 3 {

 						// Initiate the cleanup only once

 						if atomic.AddUint32(&interruptCount, 1) == 1 {

-							// Call cleanup handler

+							// Call the provided cleanup handler

 							cleanup()

 							os.Exit(0)

 						} else {

 							return

 						}

 					} else {

-						logrus.Infof("Force shutdown of docker, interrupting cleanup")

+						// 3 SIGTERM/INT signals received; force exit without cleanup

+						logrus.Infof("Forcing docker daemon shutdown without cleanup; 3 interrupts received")

 					}

 				case syscall.SIGQUIT:

+					DumpStacks()

+					logrus.Infof("Forcing docker daemon shutdown without cleanup on SIGQUIT")

 				}

+				//for the SIGINT/TERM, and SIGQUIT non-clean shutdown case, exit with 128 + signal #

 				os.Exit(128 + int(sig.(syscall.Signal)))

 			}(sig)

 		}

 	}()

 }

+

+func DumpStacks() {

+	buf := make([]byte, 16384)

+	buf = buf[:runtime.Stack(buf, true)]

+	// Note that if the daemon is started with a less-verbose log-level than "info" (the default), the goroutine

+	// traces won't show up in the log.

+	logrus.Infof("=== BEGIN goroutine stack dump ===\n%s\n=== END goroutine stack dump ===", buf)

+}