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authorOleg Nesterov <oleg@redhat.com>2015-11-06 05:48:26 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2015-11-06 06:34:48 +0300
commit4d7b3394f76ed72cfdec23ca5571dbab6ec41793 (patch)
treec32212a9df243b5e96b694f8cb9abd51138e9b5c /mm/oom_kill.c
parentc319025a6c79e532d862e3a0b9506ba316a4d13a (diff)
downloadlinux-4d7b3394f76ed72cfdec23ca5571dbab6ec41793.tar.xz
mm/oom_kill: fix the wrong task->mm == mm checks in oom_kill_process()
Both "child->mm == mm" and "p->mm != mm" checks in oom_kill_process() are wrong. task->mm can be NULL if the task is the exited group leader. This means in particular that "kill sharing same memory" loop can miss a process with a zombie leader which uses the same ->mm. Note: the process_has_mm(child, p->mm) check is still not 100% correct, p->mm can be NULL too. This is minor, but probably deserves a fix or a comment anyway. [akpm@linux-foundation.org: document process_shares_mm() a bit] Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: David Rientjes <rientjes@google.com> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Cc: Kyle Walker <kwalker@redhat.com> Cc: Stanislav Kozina <skozina@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/oom_kill.c')
-rw-r--r--mm/oom_kill.c22
1 files changed, 20 insertions, 2 deletions
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 2b6e8809d7a8..e4778285d8d1 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -474,6 +474,24 @@ void oom_killer_enable(void)
oom_killer_disabled = false;
}
+/*
+ * task->mm can be NULL if the task is the exited group leader. So to
+ * determine whether the task is using a particular mm, we examine all the
+ * task's threads: if one of those is using this mm then this task was also
+ * using it.
+ */
+static bool process_shares_mm(struct task_struct *p, struct mm_struct *mm)
+{
+ struct task_struct *t;
+
+ for_each_thread(p, t) {
+ struct mm_struct *t_mm = READ_ONCE(t->mm);
+ if (t_mm)
+ return t_mm == mm;
+ }
+ return false;
+}
+
#define K(x) ((x) << (PAGE_SHIFT-10))
/*
* Must be called while holding a reference to p, which will be released upon
@@ -521,7 +539,7 @@ void oom_kill_process(struct oom_control *oc, struct task_struct *p,
list_for_each_entry(child, &t->children, sibling) {
unsigned int child_points;
- if (child->mm == p->mm)
+ if (process_shares_mm(child, p->mm))
continue;
/*
* oom_badness() returns 0 if the thread is unkillable
@@ -575,7 +593,7 @@ void oom_kill_process(struct oom_control *oc, struct task_struct *p,
*/
rcu_read_lock();
for_each_process(p) {
- if (p->mm != mm)
+ if (!process_shares_mm(p, mm))
continue;
if (same_thread_group(p, victim))
continue;