HEADS UP: caution required with updates using custom kernels

[Brooks Davis]

Kernel config minimalists and those running aarch64 and riscv systems will
want to head this UPDATING message.

In practice, if you're fairly up to date, doing installworld before
installkernel will also work (I've tested that case from ALPHA4), but is
always somewhat risky.

-- Brooks

----- Forwarded message from Brooks Davis <brooks at FreeBSD.org> -----

Date: Thu, 23 Jun 2016 21:02:05 +0000 (UTC)
From: Brooks Davis <brooks at FreeBSD.org>
To: src-committers at freebsd.org, svn-src-all at freebsd.org,
	svn-src-head at freebsd.org
Subject: svn commit: r302152 - head

Author: brooks
Date: Thu Jun 23 21:02:05 2016
New Revision: 302152
URL: https://svnweb.freebsd.org/changeset/base/302152

Log:
  Add an UPDATING entry for the pipe() -> pipe2() transition.
  
  Approved by:	re (gjb)
  Sponsored by:	DARPA, AFRL

Modified:
  head/UPDATING

Modified: head/UPDATING
==============================================================================
--- head/UPDATING	Thu Jun 23 20:59:13 2016	(r302151)
+++ head/UPDATING	Thu Jun 23 21:02:05 2016	(r302152)
@@ -31,6 +31,14 @@ NOTE TO PEOPLE WHO THINK THAT FreeBSD 11
 	disable the most expensive debugging functionality run
 	"ln -s 'abort:false,junk:false' /etc/malloc.conf".)
 
+20160622:
+	The the libc stub for the pipe(2) system call has been replaced with
+	a wrapper which calls the pipe2(2) system call and the pipe(2) is now
+	only implemented by the kernels which include "options
+	FREEBSD10_COMPAT" in their config file (this is the default).
+	Users should ensure that this option is enabled in their kernel
+	or upgrade userspace to r302092 before upgrading their kernel.
+
 20160527:
 	CAM will now strip leading spaces from SCSI disks' serial numbers.
 	This will effect users who create UFS filesystems on SCSI disks using


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