Merge pull request #504 from crosbymichael/pid1-fixes

Fix pdeathsig and ppid for supervisor running as pid1

container_linux.go

@@ -140,7 +140,9 @@ func (c *linuxContainer) commandTemplate(p *Process, childPipe *os.File) (*exec.
 		cmd.SysProcAttr = &syscall.SysProcAttr{}
 	}
 	cmd.ExtraFiles = []*os.File{childPipe}
-	cmd.SysProcAttr.Pdeathsig = syscall.SIGKILL
+	// NOTE: when running a container with no PID namespace and the parent process spawning the container is
+	// PID1 the pdeathsig is being delivered to the container's init process by the kernel for some reason
+	// even with the parent still running.
 	if c.config.ParentDeathSignal > 0 {
 		cmd.SysProcAttr.Pdeathsig = syscall.Signal(c.config.ParentDeathSignal)
 	}

init_linux.go

@@ -69,7 +69,8 @@ func newContainerInit(t initType, pipe *os.File) (initer, error) {
 		}, nil
 	case initStandard:
 		return &linuxStandardInit{
-			config: config,
+			parentPid: syscall.Getppid(),
+			config:    config,
 		}, nil
 	}
 	return nil, fmt.Errorf("unknown init type %q", t)

standard_init_linux.go

@@ -13,7 +13,8 @@ import (
 )
 
 type linuxStandardInit struct {
-	config *initConfig
+	parentPid int
+	config    *initConfig
 }
 
 func (l *linuxStandardInit) Init() error {
@@ -85,9 +86,10 @@ func (l *linuxStandardInit) Init() error {
 	if err := pdeath.Restore(); err != nil {
 		return err
 	}
-	// Signal self if parent is already dead. Does nothing if running in a new
-	// PID namespace, as Getppid will always return 0.
-	if syscall.Getppid() == 1 {
+	// compare the parent from the inital start of the init process and make sure that it did not change.
+	// if the parent changes that means it died and we were reparened to something else so we should
+	// just kill ourself and not cause problems for someone else.
+	if syscall.Getppid() != l.parentPid {
 		return syscall.Kill(syscall.Getpid(), syscall.SIGKILL)
 	}
 	return system.Execv(l.config.Args[0], l.config.Args[0:], os.Environ())