linux-kernel - Re: [PATCH 1/4] tracing/uprobes: Revert "Support mix of ftrace and perf"

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Date:	Mon, 30 Jun 2014 22:26:26 +0530
From:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Tom Zanussi <tom.zanussi@...ux.intel.com>,
	"zhangwei(Jovi)" <jovi.zhangwei@...wei.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] tracing/uprobes: Revert "Support mix of ftrace and
 perf"

* Oleg Nesterov <oleg@...hat.com> [2014-06-27 19:01:36]:

> This reverts commit 43fe98913c9f67e3b523615ee3316f9520a623e0.
> 
> This patch is very wrong. Firstly, this change leads to unbalanced
> uprobe_unregister(). Just for example,
> 
> 	# perf probe -x /lib/libc.so.6 syscall
> 	# echo 1 >> /sys/kernel/debug/tracing/events/probe_libc/enable
> 	# perf record -e probe_libc:syscall whatever
> 
> after that uprobe is dead (unregistered) but the user of ftrace/perf
> can't know this, and it looks as if nobody hits this probe.
> 
> This would be easy to fix, but there are other reasons why it is not
> simple to mix ftrace and perf. If nothing else, they can't share the
> same ->consumer.filter. This is fixable too, but probably we need to
> fix the poorly designed uprobe_register() interface first. At least
> "register" and "apply" should be clearly separated.
> 
> Cc: stable@...r.kernel.org # v3.14
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>

Acked-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>

-- 
Thanks and Regards
Srikar Dronamraju

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