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From: Keith Owens <kaos@sgi.com>
To: Keshavamurthy Anil S <anil.s.keshavamurthy@intel.com>
cc: Anderw Morton <akpm@osdl.org>, LKML <linux-kernel@vger.kernel.org>,
       Dean Nelson <dcn@sgi.com>, Tony Luck <tony.luck@intel.com>,
       Anath Mavinakayanahalli <ananth@in.ibm.com>,
       Prasanna Panchamukhi <prasanna@in.ibm.com>,
       Dave M <davem@davemloft.net>, Andi Kleen <ak@suse.de>
Subject: Re: [(take 2)patch 6/7] Kprobes registers for notify page fault 
In-reply-to: Your message of "Thu, 20 Apr 2006 17:38:47 MST."
             <20060420173846.B12536@unix-os.sc.intel.com> 
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Date: Fri, 21 Apr 2006 10:53:29 +1000
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Keshavamurthy Anil S (on Thu, 20 Apr 2006 17:38:47 -0700) wrote:
>On Fri, Apr 21, 2006 at 10:14:04AM +1000, Keith Owens wrote:
>> Anil S Keshavamurthy (on Thu, 20 Apr 2006 16:25:02 -0700) wrote:
>> >---
>> >@@ -654,6 +659,9 @@ static int __init init_kprobes(void)
>> > 	if (!err)
>> > 		err = register_die_notifier(&kprobe_exceptions_nb);
>> > 
>> >+	if (!err)
>> >+		err = register_page_fault_notifier(&kprobe_page_fault_nb);
>> >+
>> > 	return err;
>> > }
>> > 
>> 
>> The rest of the patches look OK, but this one does not.  init_kprobes()
>> registers the main kprobe exception handler, not the page fault
>> handler.
>I am registering for register_page_fault_notifier() and as you can see
>I am not deleting the old register_die_notifier() which is also required
>for getting notified on int3/break and single-step traps. 
>So no issues here.

Patch 7 conditionally registers a page fault handler, plus an
unregister when there are no user space probes.  Why does patch 6
unconditionally register a page fault handler?