From 2bebacef5f354871c2882c76ab70529cb47ed7d3 Mon Sep 17 00:00:00 2001
From: Tonis Tiigi <tonistiigi@gmail.com>
Date: Mon, 25 Apr 2016 10:29:49 -0700
Subject: [PATCH] Wait for the reader fifo opening to block

In a rare case exec process may return before open
gets called and the io will lock indefinitely.

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>
---
 libcontainerd/process_linux.go | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/libcontainerd/process_linux.go b/libcontainerd/process_linux.go
index 136a6e250c..3c48576fe2 100644
--- a/libcontainerd/process_linux.go
+++ b/libcontainerd/process_linux.go
@@ -79,7 +79,9 @@ func (r emptyReader) Read(b []byte) (int, error) {
 
 func openReaderFromFifo(fn string) io.Reader {
 	r, w := io.Pipe()
+	c := make(chan struct{})
 	go func() {
+		close(c)
 		stdoutf, err := os.OpenFile(fn, syscall.O_RDONLY, 0)
 		if err != nil {
 			r.CloseWithError(err)
@@ -90,6 +92,7 @@ func openReaderFromFifo(fn string) io.Reader {
 		w.Close()
 		stdoutf.Close()
 	}()
+	<-c // wait for the goroutine to get scheduled and syscall to block
 	return r
 }