linux-kernel - Re: [PATCH -tip 1/3] Pass mm->flags to binfmt core

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Message-Id: <20091113231602.2DD2C100E@magilla.sf.frob.com>
Date:	Fri, 13 Nov 2009 15:16:02 -0800 (PST)
From:	Roland McGrath <roland@...hat.com>
To:	Masami Hiramatsu <mhiramat@...hat.com>
Cc:	Ingo Molnar <mingo@...e.hu>, lkml <linux-kernel@...r.kernel.org>,
	systemtap <systemtap@...rces.redhat.com>,
	DLE <dle-develop@...ts.sourceforge.net>,
	Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>
Subject: Re: [PATCH -tip 1/3] Pass mm->flags to binfmt core_dump for bitflag
	consistency

To clarify, proc_coredump_filter_write() is the one place that can change
mm->flags during a core dump.  I don't think any other is possible while
all the other tasks sharing that mm are prevented from running.  Is there
any other way that mm->flags might change during do_coredump()?

I don't see anything wrong with this change.  But (assuming that is the
only case), there is another approach we could take instead.  That is,
have proc_coredump_filter_write() do:

	down_read(&mm->mmap_sem);
	ret = mm->core_state ? -EBUSY : 0;
	up_read(&mm->mmap_sem);

Thanks,
Roland
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