From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail177-1.suw61.mandrillapp.com ([198.2.177.1]:31645 "EHLO mail177-1.suw61.mandrillapp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752984AbcCASg6 (ORCPT ); Tue, 1 Mar 2016 13:36:58 -0500 Received: from pmta06.mandrill.prod.suw01.rsglab.com (127.0.0.1) by mail177-1.suw61.mandrillapp.com id hqngkk22rtku for ; Tue, 1 Mar 2016 18:36:56 +0000 (envelope-from ) From: Subject: Patch "uml: flush stdout before forking" has been added to the 4.4-stable tree To: , , Cc: , Message-Id: <14568574101426@kroah.com> Date: Tue, 01 Mar 2016 18:36:57 +0000 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled uml: flush stdout before forking to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: uml-flush-stdout-before-forking.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From 0754fb298f2f2719f0393491d010d46cfb25d043 Mon Sep 17 00:00:00 2001 From: Vegard Nossum Date: Fri, 18 Dec 2015 21:28:53 +0100 Subject: uml: flush stdout before forking From: Vegard Nossum 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 Signed-off-by: Richard Weinberger Signed-off-by: Greg Kroah-Hartman --- arch/um/os-Linux/start_up.c | 2 ++ 1 file changed, 2 insertions(+) --- a/arch/um/os-Linux/start_up.c +++ b/arch/um/os-Linux/start_up.c @@ -94,6 +94,8 @@ static int start_ptraced_child(void) { int pid, n, status; + fflush(stdout); + pid = fork(); if (pid == 0) ptrace_child(); Patches currently in stable-queue which might be from vegard.nossum@oracle.com are queue-4.4/uml-flush-stdout-before-forking.patch queue-4.4/uml-fix-hostfs-mknod.patch