Re: [PATCH bpf] bpf: fix nested bpf tracepoints with per-cpu data

[Steven Rostedt]

On Thu, 6 Jun 2019 19:59:18 -0700
Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx> wrote:

> On Thu, Jun 6, 2019 at 1:17 PM Matt Mullins <mmullins@xxxxxx> wrote:
> >
> > BPF_PROG_TYPE_RAW_TRACEPOINTs can be executed nested on the same CPU, as
> > they do not increment bpf_prog_active while executing.
> >
> > This enables three levels of nesting, to support
> >   - a kprobe or raw tp or perf event,
> >   - another one of the above that irq context happens to call, and
> >   - another one in nmi context  
> 
> Can NMIs be nested?

No, otherwise several things in the kernel will break.

-- Steve