Subject: Re: [PATCH v4 3.0-rc2-tip 4/22]  4: Uprobes: register/unregister
 probes.
From: Peter Zijlstra <peterz@infradead.org>
To: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>, Steven Rostedt <rostedt@goodmis.org>,
        Linux-mm <linux-mm@kvack.org>,
        Arnaldo Carvalho de Melo <acme@infradead.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
        Hugh Dickins <hughd@google.com>, Christoph Hellwig <hch@infradead.org>,
        Jonathan Corbet <corbet@lwn.net>, Thomas Gleixner <tglx@linutronix.de>,
        Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
        Oleg Nesterov <oleg@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Jim Keniston <jkenisto@linux.vnet.ibm.com>,
        Roland McGrath <roland@hack.frob.com>,
        Andi Kleen <andi@firstfloor.org>, LKML <linux-kernel@vger.kernel.org>
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References: <20110607125804.28590.92092.sendpatchset@localhost6.localdomain6>
	 <20110607125900.28590.16071.sendpatchset@localhost6.localdomain6>
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Date: Wed, 15 Jun 2011 19:41:59 +0200
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On Tue, 2011-06-07 at 18:29 +0530, Srikar Dronamraju wrote:
> 1. Use mm->owner and walk thro the thread_group of mm->owner, siblings
> of mm->owner, siblings of parent of mm->owner.  This should be
> good list to traverse. Not sure if this is an exhaustive
> enough list that all tasks that have a mm set to this mm_struct are
> walked through. 

As per copy_process():

	/*
	 * Thread groups must share signals as well, and detached threads
	 * can only be started up within the thread group.
	 */
	if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
		return ERR_PTR(-EINVAL);

	/*
	 * Shared signal handlers imply shared VM. By way of the above,
	 * thread groups also imply shared VM. Blocking this case allows
	 * for various simplifications in other code.
	 */
	if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
		return ERR_PTR(-EINVAL);

CLONE_THREAD implies CLONE_VM, but not the other way around, we
therefore would be able to CLONE_VM and not be part of the primary
owner's thread group.

This is of course all terribly sad..


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