diff options
author | Oleg Nesterov <oleg@redhat.com> | 2015-11-05 18:48:26 -0800 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2015-11-05 19:34:48 -0800 |
commit | 4d7b3394f76ed72cfdec23ca5571dbab6ec41793 (patch) | |
tree | c32212a9df243b5e96b694f8cb9abd51138e9b5c | |
parent | c319025a6c79e532d862e3a0b9506ba316a4d13a (diff) | |
download | linux-4d7b3394f76ed72cfdec23ca5571dbab6ec41793.tar.bz2 |
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>
-rw-r--r-- | mm/oom_kill.c | 22 |
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; |