From 312ac3a23a2c9dc06bf182c99ddf16d273519afd Mon Sep 17 00:00:00 2001
From: Ryan Stone <rstone@FreeBSD.org>
Date: Sat, 4 Feb 2012 16:49:29 +0000
Subject: [PATCH] Whenever a new kernel thread is spawned, explicitly clear any
 CPU affinity set on the new thread.  This prevents the thread from
 inadvertently inheriting affinity from a random sibling.

Submitted by:	attilio
Tested by:	pho
MFC after:	1 week
---
 sys/kern/kern_kthread.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/sys/kern/kern_kthread.c b/sys/kern/kern_kthread.c
index bb1246980d5b..dc3fdab8b4f9 100644
--- a/sys/kern/kern_kthread.c
+++ b/sys/kern/kern_kthread.c
@@ -29,6 +29,7 @@ __FBSDID("$FreeBSD$");
 
 #include <sys/param.h>
 #include <sys/systm.h>
+#include <sys/cpuset.h>
 #include <sys/kthread.h>
 #include <sys/lock.h>
 #include <sys/mutex.h>
@@ -117,6 +118,9 @@ kproc_create(void (*func)(void *), void *arg,
 
 	/* call the processes' main()... */
 	cpu_set_fork_handler(td, func, arg);
+
+	/* Avoid inheriting affinity from a random parent. */
+	cpuset_setthread(td->td_tid, cpuset_root);
 	thread_lock(td);
 	TD_SET_CAN_RUN(td);
 	sched_prio(td, PVM);
@@ -299,6 +303,9 @@ kthread_add(void (*func)(void *), void *arg, struct proc *p,
 
 	tidhash_add(newtd);
 
+	/* Avoid inheriting affinity from a random parent. */
+	cpuset_setthread(newtd->td_tid, cpuset_root);
+
 	/* Delay putting it on the run queue until now. */
 	if (!(flags & RFSTOPPED)) {
 		thread_lock(newtd);