​​Hi Peng,

Well, an atomic counter would suffice, and if you need to secure the counter, you could wrap it around with a server. You either need a hardware upcounter, or else a periodic event-timer that you can use to emulate a hardware upcounter; from there, you just use your upcounter for your jiffies. Libplatsupport has userspace timer drivers for most platforms we support: https://github.com/seL4/util_libs/tree/master/libplatsupport​