On Wed, 9 Jun 2010, Oleg Nesterov wrote:
> > I hope that my sentence didn't imply that it was, the point is that
> > sending a SIGKILL to a PF_EXITING task isn't necessary to make it exit,
> > it's already along the right path.
>
> Well, probably this is right...
>
> David, currently I do not know how the code looks with all patches
> applied, could you please confirm there is no problem here? I am
> looking at Linus's tree,
>
> mem_cgroup_out_of_memory:
>
> p = select_bad_process();
> oom_kill_process(p);
>
mem_cgroup_out_of_memory() does this under tasklist_lock:
retry:
p = select_bad_process(&points, mem, CONSTRAINT_MEMCG, NULL);
if (!p || PTR_ERR(p) == -1UL)
goto out;
if (oom_kill_process(p, gfp_mask, 0, points, mem,
"Memory cgroup out of memory"))
goto retry;
out:
...
> Now, again, select_bad_process() can return the dead group-leader
> of the memory-hog-thread-group.
>
select_bad_process() already has:
if ((p->flags & PF_EXITING) && p->mm) {
if (p != current)
return ERR_PTR(-1UL);
chosen = p;
*ppoints = ULONG_MAX;
}
so we can disregard the check for p == current in this case since it would
not be allocating memory without p->mm.
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