On Tue, Aug 4, 2009 at 12:14 PM, Benjamin Blum<[email protected]> wrote:
>
> Hmm, the tasklist_lock section in fork() is entirely inside the
> read-lock. Presumably then iterating the threadgroup list to take all
> rwsems is safe from a race in which one thread escapes?
>
I think so - the write-side locking would be something like:
again:
read_lock(&tasklist_lock);
find first not-yet-locked task t
while (t != group_leader) {
if (!down_write_trylock(&t->threadgroup_stability_mutex)) {
get_task_struct(t);
read_unlock(&tasklist_lock);
down_write(&t->threadgroup_stability_mutex);
put_task_struct(t);
goto again;
}
t = t->next_thread;
}
read_unlock(&tasklist_lock);
Paul
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