Merge pull request moby#3722 from coryb/runc-exec-zombie

fix process termination handling for runc exec

Author: coryb

executor/runcexecutor/executor.go

@@ -92,7 +92,7 @@ func New(opt Opt, networkProviders map[pb.NetMode]network.Provider) (executor.Ex
 
 	root := opt.Root
 
-	if err := os.MkdirAll(root, 0711); err != nil {
+	if err := os.MkdirAll(root, 0o711); err != nil {
 		return nil, errors.Wrapf(err, "failed to create %s", root)
 	}
 
@@ -205,7 +205,7 @@ func (w *runcExecutor) Run(ctx context.Context, id string, root executor.Mount,
 	}
 	bundle := filepath.Join(w.root, id)
 
-	if err := os.Mkdir(bundle, 0711); err != nil {
+	if err := os.Mkdir(bundle, 0o711); err != nil {
 		return err
 	}
 	defer os.RemoveAll(bundle)
@@ -216,7 +216,7 @@ func (w *runcExecutor) Run(ctx context.Context, id string, root executor.Mount,
 	}
 
 	rootFSPath := filepath.Join(bundle, "rootfs")
-	if err := idtools.MkdirAllAndChown(rootFSPath, 0700, identity); err != nil {
+	if err := idtools.MkdirAllAndChown(rootFSPath, 0o700, identity); err != nil {
 		return err
 	}
 	if err := mount.All(rootMount, rootFSPath); err != nil {
@@ -270,7 +270,7 @@ func (w *runcExecutor) Run(ctx context.Context, id string, root executor.Mount,
 		return errors.Wrapf(err, "working dir %s points to invalid target", newp)
 	}
 	if _, err := os.Stat(newp); err != nil {
-		if err := idtools.MkdirAllAndChown(newp, 0755, identity); err != nil {
+		if err := idtools.MkdirAllAndChown(newp, 0o755, identity); err != nil {
 			return errors.Wrapf(err, "failed to create working directory %s", newp)
 		}
 	}
@@ -287,50 +287,17 @@ func (w *runcExecutor) Run(ctx context.Context, id string, root executor.Mount,
 		return err
 	}
 
-	// runCtx/killCtx is used for extra check in case the kill command blocks
-	runCtx, cancelRun := context.WithCancel(context.Background())
-	defer cancelRun()
-
-	ended := make(chan struct{})
-	go func() {
-		for {
-			select {
-			case <-ctx.Done():
-				killCtx, timeout := context.WithTimeout(context.Background(), 7*time.Second)
-				if err := w.runc.Kill(killCtx, id, int(syscall.SIGKILL), nil); err != nil {
-					bklog.G(ctx).Errorf("failed to kill runc %s: %+v", id, err)
-					select {
-					case <-killCtx.Done():
-						timeout()
-						cancelRun()
-						return
-					default:
-					}
-				}
-				timeout()
-				select {
-				case <-time.After(50 * time.Millisecond):
-				case <-ended:
-					return
-				}
-			case <-ended:
-				return
-			}
-		}
-	}()
-
 	bklog.G(ctx).Debugf("> creating %s %v", id, meta.Args)
 
 	trace.SpanFromContext(ctx).AddEvent("Container created")
-	err = w.run(runCtx, id, bundle, process, func() {
+	err = w.run(ctx, id, bundle, process, func() {
 		startedOnce.Do(func() {
 			trace.SpanFromContext(ctx).AddEvent("Container started")
 			if started != nil {
 				close(started)
 			}
 		})
 	})
-	close(ended)
 	return exitError(ctx, err)
 }
 
@@ -462,23 +429,87 @@ func (s *forwardIO) Stderr() io.ReadCloser {
 	return nil
 }
 
-// startingProcess is to track the os process so we can send signals to it.
-type startingProcess struct {
-	Process *os.Process
-	ready   chan struct{}
+// procHandle is to track the os process so we can send signals to it.
+type procHandle struct {
+	Process  *os.Process
+	ready    chan struct{}
+	ended    chan struct{}
+	shutdown func()
 }
 
-// Release will free resources with a startingProcess.
-func (p *startingProcess) Release() {
+// runcProcessHandle will create a procHandle that will be monitored, where
+// on ctx.Done the process will be killed.  If the kill fails, then the cancel
+// will be called.  This is to allow for runc to go through its normal shutdown
+// procedure if the ctx is canceled and to ensure there are no zombie processes
+// left by runc.
+func runcProcessHandle(ctx context.Context, id string) (*procHandle, context.Context) {
+	runcCtx, cancel := context.WithCancel(context.Background())
+	p := &procHandle{
+		ready:    make(chan struct{}),
+		ended:    make(chan struct{}),
+		shutdown: cancel,
+	}
+	// preserve the logger on the context used for the runc process handling
+	runcCtx = bklog.WithLogger(runcCtx, bklog.G(ctx))
+
+	go func() {
+		// Wait for pid
+		select {
+		case <-ctx.Done():
+			return // nothing to kill
+		case <-p.ready:
+		}
+
+		for {
+			select {
+			case <-ctx.Done():
+				killCtx, timeout := context.WithTimeout(context.Background(), 7*time.Second)
+				if err := p.Process.Kill(); err != nil {
+					bklog.G(ctx).Errorf("failed to kill runc %s: %+v", id, err)
+					select {
+					case <-killCtx.Done():
+						timeout()
+						cancel()
+						return
+					default:
+					}
+				}
+				timeout()
+				select {
+				case <-time.After(50 * time.Millisecond):
+				case <-p.ended:
+					return
+				}
+			case <-p.ended:
+				return
+			}
+		}
+	}()
+
+	return p, runcCtx
+}
+
+// Release will free resources with a procHandle.
+func (p *procHandle) Release() {
+	close(p.ended)
 	if p.Process != nil {
 		p.Process.Release()
 	}
 }
 
+// Shutdown should be called after the runc process has exited. This will allow
+// the signal handling and tty resize loops to exit, terminating the
+// goroutines.
+func (p *procHandle) Shutdown() {
+	if p.shutdown != nil {
+		p.shutdown()
+	}
+}
+
 // WaitForReady will wait until the Process has been populated or the
 // provided context was cancelled.  This should be called before using
 // the Process field.
-func (p *startingProcess) WaitForReady(ctx context.Context) error {
+func (p *procHandle) WaitForReady(ctx context.Context) error {
 	select {
 	case <-ctx.Done():
 		return ctx.Err()
@@ -490,7 +521,7 @@ func (p *startingProcess) WaitForReady(ctx context.Context) error {
 // WaitForStart will record the pid reported by Runc via the channel.
 // We wait for up to 10s for the runc process to start.  If the started
 // callback is non-nil it will be called after receiving the pid.
-func (p *startingProcess) WaitForStart(ctx context.Context, startedCh <-chan int, started func()) error {
+func (p *procHandle) WaitForStart(ctx context.Context, startedCh <-chan int, started func()) error {
 	startedCtx, timeout := context.WithTimeout(ctx, 10*time.Second)
 	defer timeout()
 	var err error
@@ -515,7 +546,7 @@ func (p *startingProcess) WaitForStart(ctx context.Context, startedCh <-chan int
 
 // handleSignals will wait until the runcProcess is ready then will
 // send each signal received on the channel to the process.
-func handleSignals(ctx context.Context, runcProcess *startingProcess, signals <-chan syscall.Signal) error {
+func handleSignals(ctx context.Context, runcProcess *procHandle, signals <-chan syscall.Signal) error {
 	if signals == nil {
 		return nil
 	}

executor/runcexecutor/executor_common.go

@@ -49,23 +49,20 @@ type runcCall func(ctx context.Context, started chan<- int, io runc.IO) error
 // is only supported for linux, so this really just handles signal propagation
 // to the started runc process.
 func (w *runcExecutor) commonCall(ctx context.Context, id, bundle string, process executor.ProcessInfo, started func(), call runcCall) error {
-	runcProcess := &startingProcess{
-		ready: make(chan struct{}),
-	}
+	runcProcess, ctx := runcProcessHandle(ctx, id)
 	defer runcProcess.Release()
 
-	var eg errgroup.Group
-	egCtx, cancel := context.WithCancel(ctx)
+	eg, ctx := errgroup.WithContext(ctx)
 	defer eg.Wait()
-	defer cancel()
+	defer runcProcess.Shutdown()
 
 	startedCh := make(chan int, 1)
 	eg.Go(func() error {
-		return runcProcess.WaitForStart(egCtx, startedCh, started)
+		return runcProcess.WaitForStart(ctx, startedCh, started)
 	})
 
 	eg.Go(func() error {
-		return handleSignals(egCtx, runcProcess, process.Signal)
+		return handleSignals(ctx, runcProcess, process.Signal)
 	})
 
 	return call(ctx, startedCh, &forwardIO{stdin: process.Stdin, stdout: process.Stdout, stderr: process.Stderr})

executor/runcexecutor/executor_linux.go

@@ -44,23 +44,20 @@ func (w *runcExecutor) exec(ctx context.Context, id, bundle string, specsProcess
 type runcCall func(ctx context.Context, started chan<- int, io runc.IO) error
 
 func (w *runcExecutor) callWithIO(ctx context.Context, id, bundle string, process executor.ProcessInfo, started func(), call runcCall) error {
-	runcProcess := &startingProcess{
-		ready: make(chan struct{}),
-	}
+	runcProcess, ctx := runcProcessHandle(ctx, id)
 	defer runcProcess.Release()
 
-	var eg errgroup.Group
-	egCtx, cancel := context.WithCancel(ctx)
+	eg, ctx := errgroup.WithContext(ctx)
 	defer eg.Wait()
-	defer cancel()
+	defer runcProcess.Shutdown()
 
 	startedCh := make(chan int, 1)
 	eg.Go(func() error {
-		return runcProcess.WaitForStart(egCtx, startedCh, started)
+		return runcProcess.WaitForStart(ctx, startedCh, started)
 	})
 
 	eg.Go(func() error {
-		return handleSignals(egCtx, runcProcess, process.Signal)
+		return handleSignals(ctx, runcProcess, process.Signal)
 	})
 
 	if !process.Meta.Tty {
@@ -84,7 +81,7 @@ func (w *runcExecutor) callWithIO(ctx context.Context, id, bundle string, proces
 		}
 		pts.Close()
 		ptm.Close()
-		cancel() // this will shutdown resize and signal loops
+		runcProcess.Shutdown()
 		err := eg.Wait()
 		if err != nil {
 			bklog.G(ctx).Warningf("error while shutting down tty io: %s", err)
@@ -119,13 +116,13 @@ func (w *runcExecutor) callWithIO(ctx context.Context, id, bundle string, proces
 	}
 
 	eg.Go(func() error {
-		err := runcProcess.WaitForReady(egCtx)
+		err := runcProcess.WaitForReady(ctx)
 		if err != nil {
 			return err
 		}
 		for {
 			select {
-			case <-egCtx.Done():
+			case <-ctx.Done():
 				return nil
 			case resize := <-process.Resize:
 				err = ptm.Resize(console.WinSize{