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Subject: Re: [PATCHv11 2.6.36-rc2-tip 3/15]  3: uprobes: Slot allocation
 for Execution out of line(XOL)
From: Peter Zijlstra <peterz@infradead.org>
To: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
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Date: Mon, 06 Sep 2010 20:20:24 +0200
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On Mon, 2010-09-06 at 23:29 +0530, Srikar Dronamraju wrote:
> 
> Lets say the thread while singlestepping the process gets
> pre-empted. Eventually the cpu might run some other thread of the same
> process before picking the first run thread. Or the first run
> thread could after migration due to load balancing or whatever end up
> running on  a different thread?  How do we handle these cases? 

So assuming we're preempted while the IP is inside the slot:

On the preempt-out we store the slot relative ip (ip - start_of_slot),
on preempt-in we write the replacement instructions in our cpu slot
(could be the same cpu, could be another) and re-position the ip to
point to the same relative position inside that slot, then go!

It really doesn't matter what happens in between.