linux-kernel - Re: [PATCH v11 tip 6/9] samples: bpf: simple non-portable kprobe filter example

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Message-ID: <5518A00A.5090004@plumgrid.com>
Date:	Sun, 29 Mar 2015 17:59:54 -0700
From:	Alexei Starovoitov <ast@...mgrid.com>
To:	Jovi Zhangwei <jovi.zhangwei@...il.com>
CC:	Ingo Molnar <mingo@...nel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Jiri Olsa <jolsa@...hat.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	"David S. Miller" <davem@...emloft.net>,
	Daniel Borkmann <daniel@...earbox.net>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	linux-api@...r.kernel.org, netdev@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v11 tip 6/9] samples: bpf: simple non-portable kprobe
 filter example

On 3/29/15 5:34 PM, Jovi Zhangwei wrote:
>> +               snprintf(buf, sizeof(buf),
>> +                        "echo '%c:%s %s' >> /sys/kernel/debug/tracing/kprobe_events",
>> +                        is_kprobe ? 'p' : 'r', event, event);
>> +               err = system(buf);
>
> Maybe we need to remember cleanup the kprobe_events in debugfs?

the real tracing tool should be cleaning it up. This is sample code.
I didn't want to overcomplicate it with a chain of ctrl-c handlers.
Notice patch 7 is simply doing signal(SIGINT, int_exit) and prints
histogram when process is terminated. The kprobe cleaning logic would
have interfere with this and overall would have made these samples
unnecessary complex.

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