On 08/12, Rik van Riel wrote:
>
> Any other ideas?
To simplify, lets suppose that we only need sum_exec_runtime.
Perhaps we can do something like this
u64 thread_group_sched_runtime(void)
{
struct task_struct *tsk = current;
spinlock_t *siglock = &tsk->sighand->siglock; /* stable */
struct task_struct *t;
u64 x1, x2;
retry:
x1 = tsk->signal->sum_sched_runtime;
rmb();
spin_unlock_wait(siglock);
rmb();
x2 = 0;
rcu_read_lock();
for_each_thread(tsk, t)
x2 += task_sched_runtime(t);
rcu_read_unlock();
rmb();
spin_unlock_wait(siglock);
rmb();
if (x1 != tsk->signal->sum_sched_runtime)
goto retry;
return x1 + x2;
}
?
We do not care if for_each_thread() misses the new thread, we can pretend
thread_group_sched_runtime() was called before clone.
We do not care if a thread with sum_sched_runtime == 0 exits, obviously.
Otherwise "x1 != tsk->signal->sum_sched_runtime" should tell us that we
raced with __exit_signal().
Oleg.
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