From 9e089a7d1299db498f121e17b5f68f0cc3c40953 Mon Sep 17 00:00:00 2001
From: Markus Reiter <me@reitermark.us>
Date: Fri, 21 Apr 2017 07:11:40 +0200
Subject: [PATCH] Fix `IO#select` blocking.

---
 .../Homebrew/cask/lib/hbc/system_command.rb    | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/Library/Homebrew/cask/lib/hbc/system_command.rb b/Library/Homebrew/cask/lib/hbc/system_command.rb
index c14079bc8b..65e54b4479 100644
--- a/Library/Homebrew/cask/lib/hbc/system_command.rb
+++ b/Library/Homebrew/cask/lib/hbc/system_command.rb
@@ -91,18 +91,32 @@ module Hbc
     end
 
     def each_line_from(sources)
+      tries = 3
+
       loop do
-        readable_sources = IO.select(sources)[0]
-        readable_sources.delete_if(&:eof?).first(1).each do |source|
+        selected_sources = IO.select(sources, [], [], 1)
+
+        if selected_sources.nil?
+          next unless (tries -= 1).zero?
+          odebug "IO#select failed, skipping line."
+          break
+        end
+
+        readable_sources = selected_sources[0].delete_if(&:eof?)
+
+        readable_sources.each do |source|
           type = (source == sources[0] ? :stdout : :stderr)
+
           begin
             yield(type, source.readline_nonblock || "")
           rescue IO::WaitReadable, EOFError
             next
           end
         end
+
         break if readable_sources.empty?
       end
+
       sources.each(&:close_read)
     end