Re: [PATCH] kprobes: Do not increment probe miss count in the fault handler

From: Peter Zijlstra
Date: Tue Jun 01 2021 - 09:20:49 EST


On Tue, Jun 01, 2021 at 05:31:50PM +0530, Naveen N. Rao wrote:
> Kprobes has a counter 'nmissed', that is used to count the number of
> times a probe handler was not called. This generally happens when we hit
> a kprobe while handling another kprobe.
>
> However, if one of the probe handlers causes a fault, we are currently
> incrementing 'nmissed'. The comment in fault handler indicates that this
> can be used to account faults taken by the probe handlers. But, this has
> never been the intention as is evident from the comment above 'nmissed'
> in 'struct kprobe':
>
> /*count the number of times this probe was temporarily disarmed */
> unsigned long nmissed;
>
> Signed-off-by: Naveen N. Rao <naveen.n.rao@xxxxxxxxxxxxxxxxxx>
> ---
> I'm posting this here so that these can go together, if the patch is ok
> otherwise.

I had the other two queued in perf/core and was about to push then to
tip, Masami are you good with adding this on top?