[lkml]   [2012]   [Mar]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
Patch in this message
Subject[34-longterm 188/196] taskstats: don't allow duplicate entries in listener mode
From: Vasiliy Kulikov <>

This is a commit scheduled for the next v2.6.34 longterm release.
If you see a problem with using this for longterm, please comment.

commit 26c4caea9d697043cc5a458b96411b86d7f6babd upstream.

Currently a single process may register exit handlers unlimited times.
It may lead to a bloated listeners chain and very slow process

kernel memory is stolen for the handlers chain and "time id" shows 2-7
seconds instead of normal 0.003. It makes it possible to exhaust all
kernel memory and to eat much of CPU time by triggerring numerous exits
on a single CPU.

The patch limits the number of times a single process may register
itself on a single CPU to one.

One little issue is kept unfixed - as taskstats_exit() is called before
exit_files() in do_exit(), the orphaned listener entry (if it was not
explicitly deregistered) is kept until the next someone's exit() and
implicit deregistration in send_cpu_listeners(). So, if a process
registered itself as a listener exits and the next spawned process gets
the same pid, it would inherit taskstats attributes.

Signed-off-by: Vasiliy Kulikov <>
Cc: Balbir Singh <>
Signed-off-by: Andrew Morton <>
Signed-off-by: Linus Torvalds <>
Signed-off-by: Paul Gortmaker <>
kernel/taskstats.c | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/kernel/taskstats.c b/kernel/taskstats.c
index 11281d5..5e21645 100644
--- a/kernel/taskstats.c
+++ b/kernel/taskstats.c
@@ -292,16 +292,18 @@ ret:
static int add_del_listener(pid_t pid, const struct cpumask *mask, int isadd)
struct listener_list *listeners;
- struct listener *s, *tmp;
+ struct listener *s, *tmp, *s2;
unsigned int cpu;

if (!cpumask_subset(mask, cpu_possible_mask))
return -EINVAL;

+ s = NULL;
if (isadd == REGISTER) {
for_each_cpu(cpu, mask) {
- s = kmalloc_node(sizeof(struct listener), GFP_KERNEL,
- cpu_to_node(cpu));
+ if (!s)
+ s = kmalloc_node(sizeof(struct listener),
+ GFP_KERNEL, cpu_to_node(cpu));
if (!s)
goto cleanup;
s->pid = pid;
@@ -310,9 +312,16 @@ static int add_del_listener(pid_t pid, const struct cpumask *mask, int isadd)

listeners = &per_cpu(listener_array, cpu);
+ list_for_each_entry_safe(s2, tmp, &listeners->list, list) {
+ if (s2->pid == pid)
+ goto next_cpu;
+ }
list_add(&s->list, &listeners->list);
+ s = NULL;
+ kfree(s);
return 0;


 \ /
  Last update: 2012-03-13 01:29    [W:0.687 / U:0.248 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site