Re: [PATCH 0/2] initial while_each_thread() fixes

[Oleg Nesterov]

On 12/02, Oleg Nesterov wrote:
>
> The lockless while_each_thread() is racy and broken, almost
> every user can loop forever.
> ...
> Another problem with while_each_thread() is that it is very easy
> to use it wrongly, and oom_kill.c is the good example.

Forgot to mention, it is not necessarily safe even under task
list lock if it is used wrongly. Again, oom_kill.c is the good
example, oom_kill_process() does read_lock(&tasklist_lock) but
it doesn't verify that p is still alive.

The new for_each_thread() is much simpler in this respect, it
only needs the stable task_struct.

Oleg.

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