On Thu, 10 Oct 2013 11:49:15 -0700
Linus Torvalds <torva...@linux-foundation.org> wrote:
> Oh, and I'm sure there are several users that currently depend on
> being able to sleep over get_online_cpu's. But I'm pretty sure it's
> "several", not "hundreds", and I think we could fix them up.
I'm wondering if we can have a for_each_cpu() that only disables
preemption in the loop. That is, each iteration will enable preemption,
but the loop itself will guarantee that the current cpu to process
still exists.
rcu_read_lock();
for_each_cpu(cpu, mask) {
rcu_read_unlock();
rcu_read_lock();
if (!cpu_online(cpu))
continue;
[...]
}
rcu_read_unlock();
That way expensive loops wont stop the current CPU to process all
online CPUs.
Of course, it will miss a CPU that comes online. But it would still
need to handle the case of a CPU coming online after the final
put_online_cpus(), so I'm not sure that's a problem.
-- Steve
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