sched/numa: Call task_numa_free() from do_execve()

It is possible for a task in a numa group to call exec, and
have the new (unrelated) executable inherit the numa group
association from its former self.

This has the potential to break numa grouping, and is trivial
to fix.

Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1381141781-10992-51-git-send-email-mgorman@suse.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

kernel/sched/fair.c

@@ -1418,6 +1418,7 @@ void task_numa_free(struct task_struct *p)
 {
 	struct numa_group *grp = p->numa_group;
 	int i;
+	void *numa_faults = p->numa_faults;
 
 	if (grp) {
 		for (i = 0; i < 2*nr_node_ids; i++)
@@ -1433,7 +1434,9 @@ void task_numa_free(struct task_struct *p)
 		put_numa_group(grp);
 	}
 
-	kfree(p->numa_faults);
+	p->numa_faults = NULL;
+	p->numa_faults_buffer = NULL;
+	kfree(numa_faults);
 }
 
 /*
@@ -1452,6 +1455,10 @@ void task_numa_fault(int last_cpupid, int node, int pages, int flags)
 	if (!p->mm)
 		return;
 
+	/* Do not worry about placement if exiting */
+	if (p->state == TASK_DEAD)
+		return;
+
 	/* Allocate buffer to track faults on a per-node basis */
 	if (unlikely(!p->numa_faults)) {
 		int size = sizeof(*p->numa_faults) * 2 * nr_node_ids;

kernel/sched/sched.h

@@ -559,11 +559,6 @@ static inline u64 rq_clock_task(struct rq *rq)
 #ifdef CONFIG_NUMA_BALANCING
 extern int migrate_task_to(struct task_struct *p, int cpu);
 extern int migrate_swap(struct task_struct *, struct task_struct *);
-extern void task_numa_free(struct task_struct *p);
-#else /* CONFIG_NUMA_BALANCING */
-static inline void task_numa_free(struct task_struct *p)
-{
-}
 #endif /* CONFIG_NUMA_BALANCING */
 
 #ifdef CONFIG_SMP