Re: [PATCH 2/2] mm/linux-next: Fix rcu locking in vm_is_stack

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On Wed, Mar 7, 2012 at 9:08 PM, Oleg Nesterov <oleg@xxxxxxxxxx> wrote:
> Once again. You have the task_struct *task. It exits,
> but task->thread_group->next still points to another thread T. Now suppose
> that T exits too. But task->thread_group->next was not changed, it still
> points to T. RCU grace period passes, T is freed.
> After that you take rcu_read_lock(), but it is too late! >next points to
> the already freed/reused memory. How can list_first_entry_rcu() help?

Ahh, I completely misunderstood your point. Thanks for the detailed explanation.

> And. Imho it is not good to have the (afaics exactly?) same code in
> mm/nommu.c, even with the same names. Why it is not possible to make
> a single definition?

Yes it is the same code. I put the code in both memory.c and nommu.c
because I thought they fit in there logically. I can find a common
place for it.

Siddhesh Poyarekar
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