From 00ca7552317bb69ce8eb84582d658d5e52997394 Mon Sep 17 00:00:00 2001
From: John Hawkinson <jhawk@mit.edu>
Date: Fri, 21 Oct 2016 20:44:49 -0400
Subject: [PATCH 1/3] [get_exe_version] Do version probes with <&-

When doing version probes for ffmpeg, do the
equivalent of calling it as:

    ffmpeg -version <&-

Where <&- is shell syntax for closing stdin before calling the
program. This is roughly equivalent to </dev/null without actually
opening /dev/null.

This prevents ffmpeg -version from hanging when run in the background.
Fixes #955.

The reason is that ffmpeg tries to manipulate stdin to set up terminal
characteristic, and that causes the kernel to suspend the parent
process (youtube-dl).

Note that closing stdin is achieved by calling subprocess.Popen() with
stdin set to subprocess.PIPE and without passing any input to
Popen.communicate(). This is somewhat subtle.
---
 youtube_dl/utils.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/youtube_dl/utils.py b/youtube_dl/utils.py
index 28941673fa..a89ff6908b 100644
--- a/youtube_dl/utils.py
+++ b/youtube_dl/utils.py
@@ -1820,6 +1820,7 @@ def get_exe_version(exe, args=['--version'],
     try:
         out, _ = subprocess.Popen(
             [encodeArgument(exe)] + args,
+            stdin=subprocess.PIPE,
             stdout=subprocess.PIPE, stderr=subprocess.STDOUT).communicate()
     except OSError:
         return False

From b64d04c119cd835683b95c13667dbae5db8b939f Mon Sep 17 00:00:00 2001
From: Yen Chi Hsuan <yan12125@gmail.com>
Date: Sat, 22 Oct 2016 13:04:05 +0800
Subject: [PATCH 2/3] [utils] Clarify for redirecting STDIN  in
 get_exe_version()

---
 youtube_dl/utils.py | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/youtube_dl/utils.py b/youtube_dl/utils.py
index a89ff6908b..2770c5f1c5 100644
--- a/youtube_dl/utils.py
+++ b/youtube_dl/utils.py
@@ -1818,6 +1818,9 @@ def get_exe_version(exe, args=['--version'],
     """ Returns the version of the specified executable,
     or False if the executable is not present """
     try:
+        # STDIN should be redirected too. On UNIX-like systems, ffmpeg triggers
+        # SIGTTOU if youtube-dl is run in the background.
+        # See https://github.com/rg3/youtube-dl/issues/955#issuecomment-209789656
         out, _ = subprocess.Popen(
             [encodeArgument(exe)] + args,
             stdin=subprocess.PIPE,

From 5378f8ce0d59d0a948d2597b175b2b1cff3e8bb2 Mon Sep 17 00:00:00 2001
From: Yen Chi Hsuan <yan12125@gmail.com>
Date: Sat, 22 Oct 2016 13:08:56 +0800
Subject: [PATCH 3/3] [ChangeLog] Update for #10996

---
 ChangeLog | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/ChangeLog b/ChangeLog
index 4987fb7ca6..825e357a4a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+version <unreleased>
+
+Core
+* Running youtube-dl in the background is fixed (#10996, #10706, #955)
+
+
 version 2016.10.21.1
 
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