The current PF_EXITING check in select_bad_process() is very limited,
it only works if the task is single-threaded.
Add the new helper which tries to handle the mt case. It is not exactly
clear what should we actually check in this case. This patch checks
PF_EXITING, but perhaps we can take signal_group_exit() into account.
In this case select_bad_process() could detect the exiting process even
before every thread calls exit().
Note:
- "if (p != current)" check is obviously wrong in mt case too.
- with or without this change, we should probably check
mm->core_state == NULL. We shouldn't assume that is is going
to exit "soon" otherwise. But this needs other changes anyway,
and in the common case when we do not share ->mm with another
process the false positive is not possible.
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
---
mm/oom_kill.c | 17 ++++++++++++++++-
1 file changed, 16 insertions(+), 1 deletion(-)
--- 38/mm/oom_kill.c~detect_exiting 2011-03-10 16:08:51.000000000 +0100
+++ 38/mm/oom_kill.c 2011-03-10 18:12:35.000000000 +0100
@@ -282,6 +282,21 @@ static enum oom_constraint constrained_a
}
#endif
+static bool mm_is_exiting(struct task_struct *p)
+{
+ struct task_struct *t;
+ bool has_mm = false;
+
+ do {
+ if (!(t->flags & PF_EXITING))
+ return false;
+ if (t->mm)
+ has_mm = true;
+ } while_each_thread(p, t);
+
+ return has_mm;
+}
+
/*
* Simple selection loop. We chose the process with the highest
* number of 'points'. We expect the caller will lock the tasklist.
@@ -324,7 +339,7 @@ static struct task_struct *select_bad_pr
* the process of exiting and releasing its resources.
* Otherwise we could get an easy OOM deadlock.
*/
- if (thread_group_empty(p) && (p->flags & PF_EXITING) && p->mm) {
+ if (mm_is_exiting(p)) {
if (p != current)
return ERR_PTR(-1UL);
--
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