Messages in this thread Patch in this message | | | Date | Wed, 30 Sep 2015 20:24:11 +0200 | From | Oleg Nesterov <> | Subject | [PATCH -mm v2 3/3] mm/oom_kill: fix the wrong task->mm == mm checks in oom_kill_process() |
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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.
Signed-off-by: Oleg Nesterov <oleg@redhat.com> --- mm/oom_kill.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-)
diff --git a/mm/oom_kill.c b/mm/oom_kill.c index c189ee5..034d219 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -483,6 +483,18 @@ void oom_killer_enable(void) oom_killer_disabled = false; } +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 @@ -530,7 +542,7 @@ 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 @@ -584,7 +596,7 @@ 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; -- 2.4.3
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