[PATCH 3.12 002/146] oom_kill: change oom_kill.c to use for_each_thread()

Jiri Slaby
2014-06-09T09:42:08Z

From: Oleg Nesterov <oleg@redhat.com>

3.12-stable review patch. If anyone has any objections, please let me know.

===============

commit 1da4db0cd5c8a31d4468ec906b413e75e604b465 upstream.

Change oom_kill.c to use for_each_thread() rather than the racy
while_each_thread() which can loop forever if we race with exit.

Note also that most users were buggy even if while_each_thread() was
fine, the task can exit even _before_ rcu_read_lock().

Fortunately the new for_each_thread() only requires the stable
task_struct, so this change fixes both problems.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Sergey Dyasly <dserrg@gmail.com>
Tested-by: Sergey Dyasly <dserrg@gmail.com>
Reviewed-by: Sameer Nanda <snanda@chromium.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mandeep Singh Baines <msb@chromium.org>
Cc: "Ma, Xindong" <xindong.ma@intel.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Cc: "Tu, Xiaobing" <xiaobing.tu@intel.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
mm/oom_kill.c | 20 ++++++++++----------
1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index e73f01c56d10..cae791c15c51 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -59,7 +59,7 @@ static bool has_intersects_mems_allowed(struct task_struct *tsk,
{
struct task_struct *start = tsk;

- do {
+ for_each_thread(start, tsk) {
if (mask) {
/*
* If this is a mempolicy constrained oom, tsk's
@@ -77,7 +77,7 @@ static bool has_intersects_mems_allowed(struct task_struct *tsk,
if (cpuset_mems_allowed_intersects(current, tsk))
return true;
}
- } while_each_thread(start, tsk);
+ }

return false;
}
@@ -97,14 +97,14 @@ static bool has_intersects_mems_allowed(struct task_struct *tsk,
*/
struct task_struct *find_lock_task_mm(struct task_struct *p)
{
- struct task_struct *t = p;
+ struct task_struct *t;

- do {
+ for_each_thread(p, t) {
task_lock(t);
if (likely(t->mm))
return t;
task_unlock(t);
- } while_each_thread(p, t);
+ }

return NULL;
}
@@ -301,7 +301,7 @@ static struct task_struct *select_bad_process(unsigned int *ppoints,
unsigned long chosen_points = 0;

rcu_read_lock();
- do_each_thread(g, p) {
+ for_each_process_thread(g, p) {
unsigned int points;

switch (oom_scan_process_thread(p, totalpages, nodemask,
@@ -323,7 +323,7 @@ static struct task_struct *select_bad_process(unsigned int *ppoints,
chosen = p;
chosen_points = points;
}
- } while_each_thread(g, p);
+ }
if (chosen)
get_task_struct(chosen);
rcu_read_unlock();
@@ -406,7 +406,7 @@ void oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
{
struct task_struct *victim = p;
struct task_struct *child;
- struct task_struct *t = p;
+ struct task_struct *t;
struct mm_struct *mm;
unsigned int victim_points = 0;
static DEFINE_RATELIMIT_STATE(oom_rs, DEFAULT_RATELIMIT_INTERVAL,
@@ -437,7 +437,7 @@ void oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
* still freeing memory.
*/
read_lock(&tasklist_lock);
- do {
+ for_each_thread(p, t) {
list_for_each_entry(child, &t->children, sibling) {
unsigned int child_points;

@@ -455,7 +455,7 @@ void oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
get_task_struct(victim);
}
}
- } while_each_thread(p, t);
+ }
read_unlock(&tasklist_lock);

rcu_read_lock();
--
1.9.3