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SubjectRe: [PATCH -mm] swsusp: freeze user space processes first
On Ne 05-02-06 11:50:37, Ingo Molnar wrote:
>
> * Rafael J. Wysocki <rjw@sisk.pl> wrote:
>
> > > The logic in that loop makes my brain burst.
> > >
> > > What happens if a process does vfork();sleep(100000000)?
> >
> > The freezing of processes will fail due to the timeout.
> >
> > Without the if (!p->vfork_done) it would fail too, because the child
> > would be frozen and the parent would wait for the vfork completion in
> > the TASK_UNINTERRUPTIBLE state (ie. unfreezeable). But in that case
> > we have a race between the "freezer" and the child process (ie. if the
> > child gets frozen before it completes the vfork completion, the paret
> > will be unfreezeable) which sometimes leads to a failure when it
> > should not. [We have a test case showing this.]
>
> then i'd suggest to change the vfork implementation to make this code
> freezable. Nothing that userspace does should cause freezing to fail.
> If it does, we've designed things incorrectly on the kernel side.

Does that also mean we have bugs with signal delivery? If vfork();
sleep(100000); causes process to be uninterruptible for few days, it
will not be killable and increase load average...
Pavel
--
Thanks, Sharp!
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