[LITMUS^RT] RFC: record interrupt interference with Feather-Trace

[Christopher Kenna]

Hi Björn,

This is a good idea. I just had a few simple questions for my own understanding.

The first is the use of the __raw_get_cpu_var function versus the
__get_cpu_var function. I was wondering in what situation to use one
versus the other? It looks like (from what I could make out in the
code) that the two functions differ only when CONFIG_DEBUG_PREEMPT is
enabled (the kernel configuration help says something about printing
warnings if kernel code uses it in a preemption-unsafe way).

The second question is why did you use a barrier in
__save_timestamp_cpu and not in save_task_latency? Can the call to
litmus_clock in save_task_latency be reordered? (It seems obvious not
to use the barrier in __add_timestamp_user, as the time to record is
passed in from user space.)

Finally, since you suggested it, I pushed our kernel to a private
repository on Github. I can add unlimited collaborators to this
repository. If you have a Github account and would like to be added,
please let me know (Björn, I already added you). I think that using
Github for private collaboration is a great idea. The interface they
have (even just for diff) is very pretty :) The reason I have this
account is because you can request a free Micro account if you are a
student, with no limit on the number of collaborators you have
<https://github.com/edu>.

 -- Chris

2012/1/27 Björn Brandenburg <bbb at mpi-sws.org>:
>
> On Jan 26, 2012, at 6:27 PM, Christopher Kenna wrote:
>> The public repository <http://www.litmus-rt.org/src/litmus-rt.git>
>> currently has a master and staging branch. I assume that development
>> stuff like this would go elsewhere.
>> If you need to reply to me
>> directly (off of the list) to talk about where to go to find them
>> and/or get a public key from me, that is okay. Alternatively, if you
>> still have your UNC account, you could push it to the CVS/git machine
>> here.
>
> I already did that when I first posted the patches. It should be in the branch wip-ft-irq-flag on the UNC servers (both cvs.cs... and  jupiter-cs.cs...).
>
> It may make sense to have public development branches at some point (bitbucket.org? github.org?), but for now I think it's easier for me to just push it to the UNC systems.
>
> - Björn
>
>
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