Re: [patch 3/14] x86, ptrace, bts: stop bts tracing early in do_exit

[Oleg Nesterov <oleg@redhat.com>]

On 03/27, Markus Metzger wrote:
>
> +static void ptrace_bts_exit(void)
> +{
> +	if (unlikely(!list_empty(&current->ptraced)))
> +		ptrace_bts_exit_tracer();
> +
> +	if (unlikely(current->bts))
> +		ptrace_bts_exit_tracee();
> +}

Could you explain why do we need ptrace_bts_exit_tracee() ?

If current is traced, the tracer should do ptrace_bts_release()
eventually, no?

And if we really need to do ptrace_bts_exit_tracee(), then
"if (unlikely(current->bts))" check is racy. The tracer
can do PTRACE_BTS_CONFIG right after the check.

Oleg.