student for gsoc2008

[Chris Johns]

Joel Sherrill wrote:
> I think entry/exit makes sense on potentially blocking
> synchronization primitives.
> Consider this sequence:
> 
> + sem obtain blocks
>   - context switch
>   time passes         - context switch back
> + sem obtain returns
> 
> At the first context switch, without logging entry we do not know why
> it blocked.  At the return point, without logging the exit we do not know
> the reason why it unblocked.
> 
> It is just something that needs to be worked through.  Do we log entry
> and exit to read()?  If you don't you won't know if that blocked you 
> forever
> or how many bytes were read.
> 
> Hard issues..

Yes this nice example where the tool is being used in real-time to debug means 
we need 2 calls. If the bug is the call never returns you never know it 
happened which is not a useful tool.

Regards
Chris