On Thu, Sep 03, 2020 at 04:22:42PM +0200, Oleg Nesterov wrote:
On 09/02, Christian Brauner wrote:
It also makes the API more consistent and uniform. In essence, waitid() is treated like a read on a non-blocking pidfd or a recvmsg() on a non-blocking socket. With the addition of support for non-blocking pidfds we support the same functionality that sockets do. For sockets() recvmsg() supports MSG_DONTWAIT for pidfds waitid() supports WNOHANG.
What I personally do not like is that waitid(WNOHANG) returns zero or EAGAIN depending on f_flags & O_NONBLOCK... This doesn't match recvmsg(MSG_DONTWAIT) and doesn't look consistent to me.
It's not my favorite thing either but async event loops are usually modeled around EAGAIN so I think this has benefits. Josh can speak more to that.
Christian