runsc: Add the "wait" subcommand.

Users can now call "runsc wait <container id>" to wait on a particular process
inside the container. -pid can also be used to wait on a specific PID.

Manually tested the wait subcommand for a single waiter and multiple waiters
(simultaneously 2 processes waiting on the container and 2 processes waiting on
a PID within the container).

PiperOrigin-RevId: 202548978
Change-Id: Idd507c2cdea613c3a14879b51cfb0f7ea3fb3d4c

1 files changed, 14 insertions, 0 deletions

diff --git a/runsc/container/container.go b/runsc/container/container.go
index b2ea78084..042c76577 100644
--- a/runsc/container/container.go
+++ b/runsc/container/container.go
@@ -353,6 +353,20 @@ func (c *Container) Wait() (syscall.WaitStatus, error) {
 	return c.Sandbox.Wait(c.ID)
 }
 
+// WaitRootPID waits for process 'pid' in the sandbox's PID namespace and
+// returns its WaitStatus.
+func (c *Container) WaitRootPID(pid int32) (syscall.WaitStatus, error) {
+	log.Debugf("Wait on pid %d in sandbox %q", pid, c.Sandbox.ID)
+	return c.Sandbox.WaitPID(pid, c.Sandbox.ID)
+}
+
+// WaitPID waits for process 'pid' in the container's PID namespace and returns
+// its WaitStatus.
+func (c *Container) WaitPID(pid int32) (syscall.WaitStatus, error) {
+	log.Debugf("Wait on pid %d in container %q", pid, c.ID)
+	return c.Sandbox.WaitPID(pid, c.ID)
+}
+
 // Signal sends the signal to the container.
 func (c *Container) Signal(sig syscall.Signal) error {
 	log.Debugf("Signal container %q", c.ID)