On 12/21, Linus Torvalds wrote:
>
> We have coredump serialization in exit_mm() that I think *should* make
> this all ok - if we still see p->mm matching our mm,
Yes. And the comment says:
lock_task_sighand(p)
must be used. Since p->mm != NULL and we hold ->mmap_sem
it can't fail.
IOW, this task can't pass exit_mm() and thus lock_task_sighand() can't
fail.
> > do {
> > if (p->mm) {
> > if (unlikely(p->mm == mm)) {
> > - lock_task_sighand(p, &flags);
> > - nr += zap_process(p, exit_code);
> > - unlock_task_sighand(p, &flags);
> > + if (lock_task_sighand(p, &flags) {
> > + nr += zap_process(p,
> > exit_code);
> > + unlock_task_sighand(p,
> > &flags);
> > + }
I too do not think this is needed. But perhaps BUG_ON() make sense.
Note: just in case, this has another problem: while_each_thread() is racy.
We already have the initial fixes in -mm, this code (as other users)
should be converted to use for_each_thread(), I'll send the patch(es).
Oleg.
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