Re: hit a KASan bug related to Perf during stress test

Peter Zijlstra
2016-10-24T12:12:10Z

On Mon, Oct 24, 2016 at 02:04:11PM +0200, Jiri Olsa wrote:
> On Mon, Oct 24, 2016 at 01:29:45PM +0200, Peter Zijlstra wrote:

> > Hurm, then again, I imagine that after unhash_process the PID/TID could
> > be instantly re-used and then we're still confused.
>
> sounds bad.. I haven't checked the related pid_alive code,
> but shouldn't we already get the EXIT event in this case?

It has, perf_event_exit_task() happens before we unhash.

But a per-cpu event that has PID/TID reporting on will run into this.

We'll observe 'funny' values between the unhash and the next context
switch.