On Wed, Jan 20, 2021 at 12:24 PM Jason Wang <jasowang@xxxxxxxxxx> wrote: > > > On 2021/1/19 下午12:59, Xie Yongji wrote: > > Now we have a global percpu counter to limit the recursion depth > > of eventfd_signal(). This can avoid deadlock or stack overflow. > > But in stack overflow case, it should be OK to increase the > > recursion depth if needed. So we add a percpu counter in eventfd_ctx > > to limit the recursion depth for deadlock case. Then it could be > > fine to increase the global percpu counter later. > > > I wonder whether or not it's worth to introduce percpu for each eventfd. > > How about simply check if eventfd_signal_count() is greater than 2? > It can't avoid deadlock in this way. So we need a percpu counter for each eventfd to limit the recursion depth for deadlock cases. And using a global percpu counter to avoid stack overflow. Thanks, Yongji
