From: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
To: Namhyung Kim <namhyung@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Ingo Molnar <mingo@kernel.org>,
Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
"yrl.pp-manager.tt@hitachi.com" <yrl.pp-manager.tt@hitachi.com>
Subject: Re: Re: [PATCH ftrace/core 2/2] ftrace, kprobes: Support IPMODIFY flag to find IP modify conflict
Date: Thu, 12 Jun 2014 15:57:43 +0900 [thread overview]
Message-ID: <53994F67.9030106@hitachi.com> (raw)
In-Reply-To: <871tuuad02.fsf@sejong.aot.lge.com>
(2014/06/12 14:54), Namhyung Kim wrote:
> On Thu, 12 Jun 2014 12:29:09 +0900, Masami Hiramatsu wrote:
>> NO, ftrace_lookup_ip() returns NULL if the hash is empty, so adding
>> !ftrace_hash_empty() is meaningless :)
>>
>> Actually, here I intended to have 3 meanings for the new/old_hash arguments,
>> - If it is NULL, it hits all
>> - If it is EMPTY_HASH, it hits nothing
>> - If it has some entries, it hits those entries.
>>
>> And in ftrace.c(__ftrace_hash_rec_update), AFAICS, ops->filter_hash has only
>> 2 meanings,
>> - If it is EMPTY_HASH or NULL, it hits all
>> - If it has some entries, it hits those entries.
>
> Then I found an unrelated issue during review.
>
> It seems that checking NULL other_hash for the 'all' case in
> __ftrace_hash_rec_update() is not sufficient. It should check
> EMPTY_HASH case too, but then it ends up removing the check at all since
> it can be covered in ftrace_lookup_ip().
I guessed that was just for speeding up by skipping ftrace_lookup_ip().
(but I'm not sure how much it improves...)
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
However, I'd like to ask Steven his Ack.
Thank you,
>
> Thanks,
> Namhyung
>
>
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index 13885590a184..8bd7aa69a479 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -1545,7 +1545,7 @@ static void __ftrace_hash_rec_update(struct ftrace_ops *ops,
> * Only the filter_hash affects all records.
> * Update if the record is not in the notrace hash.
> */
> - if (!other_hash || !ftrace_lookup_ip(other_hash, rec->ip))
> + if (!ftrace_lookup_ip(other_hash, rec->ip))
> match = 1;
> } else {
> in_hash = !!ftrace_lookup_ip(hash, rec->ip);
> --
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> Please read the FAQ at http://www.tux.org/lkml/
>
--
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com
next prev parent reply other threads:[~2014-06-12 6:57 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-10 10:50 [PATCH ftrace/core 0/2] ftrace, kprobes: Introduce IPMODIFY flag for ftrace_ops to detect conflicts Masami Hiramatsu
2014-06-10 10:50 ` [PATCH ftrace/core 1/2] ftrace: Simplify ftrace_hash_disable/enable path in ftrace_hash_move Masami Hiramatsu
2014-06-10 10:50 ` [PATCH ftrace/core 2/2] ftrace, kprobes: Support IPMODIFY flag to find IP modify conflict Masami Hiramatsu
2014-06-10 13:53 ` Namhyung Kim
2014-06-11 1:28 ` Masami Hiramatsu
2014-06-11 7:41 ` Namhyung Kim
2014-06-12 3:29 ` Masami Hiramatsu
2014-06-12 5:38 ` Namhyung Kim
2014-06-12 6:06 ` Masami Hiramatsu
2014-06-12 5:54 ` Namhyung Kim
2014-06-12 6:57 ` Masami Hiramatsu [this message]
2014-06-11 16:58 ` [PATCH ftrace/core 0/2] ftrace, kprobes: Introduce IPMODIFY flag for ftrace_ops to detect conflicts Josh Poimboeuf
2014-06-12 3:28 ` Namhyung Kim
2014-06-12 12:50 ` Josh Poimboeuf
2014-06-12 5:44 ` Masami Hiramatsu
2014-06-12 12:43 ` Josh Poimboeuf
2014-06-13 10:09 ` Masami Hiramatsu
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