On Fri, Jan 29, 2021 at 10:59:52AM -0500, Steven Rostedt wrote: > On Fri, 29 Jan 2021 22:40:11 +0900 > Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote: > > > > So what, they can all happen with random locks held. Marking them as NMI > > > enables a whole bunch of sanity checks that are entirely appropriate. > > > > How about introducing an idea of Asynchronous NMI (ANMI) and Synchronous > > NMI (SNMI)? kprobes and ftrace is synchronously called and can be controlled > > (we can expect the context) but ANMI may be caused by asynchronous > > hardware events on any context. > > > > If we can distinguish those 2 NMIs on preempt count, bpf people can easily > > avoid the inevitable situation. > > I don't like the name NMI IN SNMI, because they are not NMIs. They are > actually more like kernel exceptions. Even page faults in the kernel is > similar to a kprobe breakpoint or ftrace. It can happen anywhere, with any > lock held. Perhaps we need a kernel exception context? Which by definition > is synchronous. What problem are you trying to solve? AFAICT all these contexts have the same restrictions, why try and muck about with different names for the same thing?
