linux-kernel - Re: [for-next-3.11][PATCH 0/8] ftrace/tracing: Event file fixes and ftrace function hash fixes

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Message-ID: <20130731114722.GA4416@redhat.com>
Date:	Wed, 31 Jul 2013 13:47:22 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Subject: Re: [for-next-3.11][PATCH 0/8] ftrace/tracing: Event file fixes
	and ftrace function hash fixes

On 07/30, Steven Rostedt wrote:
>
> Using the i_private and event_mutex
> to verify that the event still exists to solve the race.

To remind, we also need the "debugfs: debugfs_remove_recursive() must
not rely on list_empty(d_subdirs)" patch, otherwise we still have the
problems with the opened files.

Just in case, we need this fix even if .open() does trace_array_get()
or tracing_open_generic_file() (removed by recent changes), rmdir can
be called before we increment the counter and the deleted dentry breaks
debugfs_remove_recursive().

But after the recent changes this fix becomes more important. An opened
file confuses debugfs_remove_recursive() and after that you can't create
another probe.

Oleg.

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