Re: [patch V6 02/37] tracing/hwlat: Split ftrace_nmi_enter/exit()

[Steven Rostedt]

On Sat, 16 May 2020 01:45:49 +0200
Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:

> The hardware latency tracer calls into timekeeping and ends up in
> various instrumentable functions which is problematic vs. the kprobe
> handling especially the text poke machinery. It's invoked from
> nmi_enter/exit(), i.e. non-instrumentable code.
> 
> Split it into two parts:
> 
>  1) NMI counter, only invoked on nmi_enter() and noinstr safe
> 
>  2) NMI timestamping, to be invoked from instrumentable code
> 
> Move it into the rcu is watching regions of nmi_enter/exit() even
> if there is no actual RCU dependency right now but there is also
> no point in having it early.
> 
> The actual split of nmi_enter/exit() is done in a separate step.
> 
> Requested-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>

Reviewed-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>

-- Steve