linux-kernel - Re: [PATCH 03/11] ftrace: Cleanup regex_lock and ftrace

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Date:	Thu, 09 May 2013 13:12:15 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc:	linux-kernel@...r.kernel.org,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	yrl.pp-manager.tt@...achi.com, Oleg Nesterov <oleg@...hat.com>,
	Ingo Molnar <mingo@...hat.com>,
	Tom Zanussi <tom.zanussi@...el.com>
Subject: Re: [PATCH 03/11] ftrace: Cleanup regex_lock and ftrace_lock around
 hash updating

On Thu, 2013-05-09 at 14:44 +0900, Masami Hiramatsu wrote:
> Cleanup regex_lock and ftrace_lock locking points around
> ftrace_ops hash update code.
> 
> The new rule is that regex_lock protects ops->*_hash
> read-update-write code for each ftrace_ops. Usually,
> hash update is done by following sequence.
> 
> 1. allocate a new local hash and copy the original hash.
> 2. update the local hash.
> 3. move(actually, copy) back the local hash to ftrace_ops.
> 4. update ftrace entries if needed.
> 5. release the local hash.
> 
> This makes regex_lock to protect #1-#4, and ftrace_lock
> to protect #3 and #4.

Patch looks good, but I don't see how ftrace_lock protects #3. The two
things that I see ftrace_lock protecting is the update to the ftrace
entries, and the adding and removing ftrace_ops to the ftrace_ops_list.

-- Steve

> 
> Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Frederic Weisbecker <fweisbec@...il.com>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Tom Zanussi <tom.zanussi@...el.com>
> ---


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