This small fix fixes 2 different issues:

• Attach after detach in master

Attaching after once detached doesn't work in current master. v1.4.1 isn't affected. Regression is at #9511.

docker run -it --name test busybox
^P^Q
docker attach test
<no prompt>

The problem is that when stdout/stderr closed cStdin.Close() is always called on if in stdinOnce mode. This closes the process stdin.

• docker attach not exiting when container exits docker attach not exiting when container exits #9860

After stdout/stderr close, stdin.Close() is only ran if we are on stdinOnce mode. Goroutine must be always cleaned. Regression is at #8571.

We never actually need to close container stdin after stdout/stderr finishes. We only need to close the stdin goroutine. In some cases this also means closing stdin but that is already controlled by the goroutine itself.

/cc @LK4D4 @jfrazelle @cpuguy83

Signed-off-by: Tonis Tiigi tonistiigi@gmail.com