Messages in this thread | | | Date | Tue, 2 Dec 2014 10:35:30 +0100 | From | Michal Hocko <> | Subject | Re: [PATCH 2/2] oom: kill the insufficient and no longer needed PT_TRACE_EXIT check |
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On Fri 28-11-14 00:04:08, Oleg Nesterov wrote: > After the previous patch we can remove the PT_TRACE_EXIT check in > oom_scan_process_thread(), it was added to handle the case when the > coredumping was "frozen" by ptrace, but it doesn't really work. If > nothing else, we would need to check all threads which could share > the same ->mm to make it more or less correct. > > Signed-off-by: Oleg Nesterov <oleg@redhat.com>
I still do not see why we do not need task->ptrace & PT_TRACE_EXIT check here. I do understand that the check on group_leader doesn't make much sense. ptrace_event would block until the tracer let the task run again which may be never AFAICS.
It is really sad how subtle and racy are all these checks :/
> --- > mm/oom_kill.c | 11 +++-------- > 1 files changed, 3 insertions(+), 8 deletions(-) > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > index 7af33b5..a2a4036 100644 > --- a/mm/oom_kill.c > +++ b/mm/oom_kill.c > @@ -287,14 +287,9 @@ enum oom_scan_t oom_scan_process_thread(struct task_struct *task, > if (oom_task_origin(task)) > return OOM_SCAN_SELECT; > > - if (task_will_free_mem(task) && !force_kill) { > - /* > - * If this task is not being ptraced on exit, then wait for it > - * to finish before killing some other task unnecessarily. > - */ > - if (!(task->group_leader->ptrace & PT_TRACE_EXIT)) > - return OOM_SCAN_ABORT; > - } > + if (task_will_free_mem(task) && !force_kill) > + return OOM_SCAN_ABORT; > + > return OOM_SCAN_OK; > } > > -- > 1.5.5.1 >
-- Michal Hocko SUSE Labs
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