[PATCH 1/2] taskstats: add_del_listener() shouldn't use the wrong node

Oleg Nesterov
2011-07-20T19:02:56Z

1. 26c4caea "don't allow duplicate entries in listener mode"
changed add_del_listener(REGISTER) so that "next_cpu:" can
reuse the listener allocated for the previous cpu, this
doesn't look exactly right even if minor.

Change the code to kfree() in the already-registered case,
this case is unlikely anyway so the extra kmalloc_node()
shouldn't hurt but looke more correct and clean.

2. use the plain list_for_each_entry() instead of _safe() to
scan listeners->list.

3. Remove the unneeded INIT_LIST_HEAD(&s->list), we are going
to list_add(&s->list).

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---

kernel/taskstats.c | 16 +++++++---------
1 file changed, 7 insertions(+), 9 deletions(-)

--- ts/kernel/taskstats.c~1_cleanup 2011-07-03 16:27:57.000000000 +0200
+++ ts/kernel/taskstats.c 2011-07-20 19:35:38.000000000 +0200
@@ -291,30 +291,28 @@ static int add_del_listener(pid_t pid, c
if (!cpumask_subset(mask, cpu_possible_mask))
return -EINVAL;

- s = NULL;
if (isadd == REGISTER) {
for_each_cpu(cpu, mask) {
- if (!s)
- s = kmalloc_node(sizeof(struct listener),
- GFP_KERNEL, cpu_to_node(cpu));
+ s = kmalloc_node(sizeof(struct listener),
+ GFP_KERNEL, cpu_to_node(cpu));
if (!s)
goto cleanup;
+
s->pid = pid;
- INIT_LIST_HEAD(&s->list);
s->valid = 1;

listeners = &per_cpu(listener_array, cpu);
down_write(&listeners->sem);
- list_for_each_entry_safe(s2, tmp, &listeners->list, list) {
+ list_for_each_entry(s2, &listeners->list, list) {
if (s2->pid == pid)
- goto next_cpu;
+ goto exists;
}
list_add(&s->list, &listeners->list);
s = NULL;
-next_cpu:
+exists:
up_write(&listeners->sem);
+ kfree(s); /* nop if NULL */
}
- kfree(s);
return 0;
}