Re: [PATCH] riscv: keep interrupts disabled for BREAKPOINT exception

[Maciej W. Rozycki]

On Fri, 9 Apr 2021, Masami Hiramatsu wrote:

> > >  Is this approach guaranteed to keep interrupt handling latency low enough
> > > for the system not to be negatively affected, e.g. for the purpose of NTP
> > > timekeeping?
> > 
> > IMHO, interrupt latency can't be ensured if kprobes is triggered.
> 
> Indeed. The latency depends on what the kprobe user handler does. Of course
> it must be as minimal as possible... On x86, it is less than a few microseconds.
> Thus it may be a jitter on hard realtime system, but not a big issue on
> usual system like NTP timekeeping.

 Ack.  Assuming that the breakpoint exception will only disable interrupts 
if kprobes are in use it seems reasonable to me.

 Thanks for double-checking.

  Maciej