From: Oleg Nesterov <oleg@xxxxxxxxxx>
This patch has been added to the 3.12 stable tree. If you have any
objections, please let us know.
===============
commit 4d4048be8a93769350efa31d2482a038b7de73d0 upstream.
find_lock_task_mm() expects it is called under rcu or tasklist lock, but
it seems that at least oom_unkillable_task()->task_in_mem_cgroup() and
mem_cgroup_out_of_memory()->oom_badness() can call it lockless.
Perhaps we could fix the callers, but this patch simply adds rcu lock
into find_lock_task_mm(). This also allows to simplify a bit one of its
callers, oom_kill_process().
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Sergey Dyasly <dserrg@xxxxxxxxx>
Cc: Sameer Nanda <snanda@xxxxxxxxxxxx>
Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Mandeep Singh Baines <msb@xxxxxxxxxxxx>
Cc: "Ma, Xindong" <xindong.ma@xxxxxxxxx>
Reviewed-by: Michal Hocko <mhocko@xxxxxxx>
Cc: "Tu, Xiaobing" <xiaobing.tu@xxxxxxxxx>
Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
mm/oom_kill.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 7cdd05e685dc..f5bed7f17463 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -102,14 +102,19 @@ struct task_struct *find_lock_task_mm(struct task_struct *p)
{
struct task_struct *t;
+ rcu_read_lock();
+
for_each_thread(p, t) {
task_lock(t);
if (likely(t->mm))
- return t;
+ goto found;
task_unlock(t);
}
+ t = NULL;
+found:
+ rcu_read_unlock();
- return NULL;
+ return t;
}
/* return true if the task is not adequate as candidate victim task. */
@@ -461,10 +466,8 @@ void oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
}
read_unlock(&tasklist_lock);
- rcu_read_lock();
p = find_lock_task_mm(victim);
if (!p) {
- rcu_read_unlock();
put_task_struct(victim);
return;
} else if (victim != p) {
@@ -490,6 +493,7 @@ void oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
* That thread will now get access to memory reserves since it has a
* pending fatal signal.
*/
+ rcu_read_lock();
for_each_process(p)
if (p->mm == mm && !same_thread_group(p, victim) &&
!(p->flags & PF_KTHREAD)) {
--
1.9.3
--
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