From 15dabec9d87dd441d6f0ce49fbbef7fcc5f1ec39 Mon Sep 17 00:00:00 2001
From: Vegard Nossum <vegard.nossum@oracle.com>
Date: Fri, 18 Dec 2015 21:28:53 +0100
Subject: [PATCH] uml: flush stdout before forking

commit 0754fb298f2f2719f0393491d010d46cfb25d043 upstream.

I was seeing some really weird behaviour where piping UML's output
somewhere would cause output to get duplicated:

  $ ./vmlinux | head -n 40
  Checking that ptrace can change system call numbers...Core dump limits :
          soft - 0
          hard - NONE
  OK
  Checking syscall emulation patch for ptrace...Core dump limits :
          soft - 0
          hard - NONE
  OK
  Checking advanced syscall emulation patch for ptrace...Core dump limits :
          soft - 0
          hard - NONE
  OK
  Core dump limits :
          soft - 0
          hard - NONE

This is because these tests do a fork() which duplicates the non-empty
stdout buffer, then glibc flushes the duplicated buffer as each child
exits.

A simple workaround is to flush before forking.

Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
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