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

1 files changed, 7 insertions, 0 deletions

diff --git a/sys/kern/kern_kthread.c b/sys/kern/kern_kthread.c
index bb12469..dc3fdab 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);