eventfd.Notify() uses unix.Write which will eventually
call unix.Syscall which will yield the current go processor
resulting in the Go scheduler parking the current goroutine
till the syscall returns.
But in most cases where Notify() is called there is no reason
to yield as the caller probably wants to continue doing something
right afterwards. Like in the case of the sharedmem endpoint
which may still have more packets to write.
PiperOrigin-RevId: 405693801
The same create/write/read pattern is copied around several places. It's easier
to understand in a package with names and comments, and we can reuse the smart
blocking code in package rawfile.
PiperOrigin-RevId: 401647108
