linux-kernel - Re: [RFC PATCH 06/10] ftrace: Release the function hlist if we don't need it anymore

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Message-ID: <4B5D3D37.4090107@cn.fujitsu.com>
Date:	Mon, 25 Jan 2010 14:41:59 +0800
From:	Lai Jiangshan <laijs@...fujitsu.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
CC:	Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Li Zefan <lizf@...fujitsu.com>
Subject: Re: [RFC PATCH 06/10] ftrace: Release the function hlist if we don't
 need it anymore

Frederic Weisbecker wrote:
> After we disable the function profiler, the function hashlist
> stays in memory. This is wasteful as nobody needs it anymore,
> until the next use if any.
> 
> Release it when we disable the function profiler instead of
> resetting it in the next use.
> 
> Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Li Zefan <lizf@...fujitsu.com>
> Cc: Lai Jiangshan <laijs@...fujitsu.com>
> ---
>  kernel/trace/ftrace.c          |    1 +
>  kernel/trace/functions_hlist.c |   61 +++++++++++++++++-----------------------
>  kernel/trace/functions_hlist.h |    1 +
>  3 files changed, 28 insertions(+), 35 deletions(-)
> 
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index dfd8f7c..0ded01c 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -509,6 +509,7 @@ ftrace_profile_write(struct file *filp, const char __user *ubuf,

>			/*
>			 * unregister_ftrace_profiler calls stop_machine
>			 * so this acts like an synchronize_sched.
>			 */
>  			unregister_ftrace_profiler();

unluckily, when !CONFIG_DYNAMIC_FTRACE, it does not call stop_machine()
nor synchronize_sched(), bug here?

> +			function_hlist_release();


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