linux-kernel - Re: [PATCH 1/2 v5 typo updated] tracing/uprobes: Support ftrace_event

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Message-ID: <20130704175712.GC2046@redhat.com>
Date:	Thu, 4 Jul 2013 19:57:12 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	"zhangwei(Jovi)" <jovi.zhangwei@...wei.com>
Cc:	Namhyung Kim <namhyung@...nel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2 v5 typo updated] tracing/uprobes: Support
	ftrace_event_file base multibuffer

On 07/04, zhangwei(Jovi) wrote:
>
> On 2013/7/4 15:41, Namhyung Kim wrote:
> >>
> >> Even though we allow multi-uprobes instances now,
> >> but TP_FLAG_PROFILE/TP_FLAG_TRACE are still mutually exclusive
> >> in probe_event_enable currently, this means we cannot allow
> >> one user is using uprobe-tracer, and another user is using
> >> perf-probe on same uprobe concurrently.
> >> (Perhaps this will be fix in future, kprobe dont't have this
> >> limitation now)
> >
> > So why does this limitation exist?  Didn't we support this kind of thing
> > in the original code?

For no reason.

> Yes, it existed(maybe not exist before uprobe pre-filter work),

No, it was always here and I never understood it.

> because uprobe filter
> is associated with trace_uprobe tightly at present, so we cannot assign
> TP_FLAG_PROFILE/TP_FLAG_TRACE for same trace_uprobe with different filter.

More precisely, TRACE_REG_REGISTER should participate (inc/dec nr_systemwide)
if CONFIG_PERF_EVENTS.

> Perhaps we need to remove the limitation in future.

Yes, I'll remove it.

Oleg.

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