Re: [PATCH 4/6] kvm tools: Add rwlock wrapper

[Ingo Molnar <mingo@elte.hu>]

* Mathieu Desnoyers <mathieu.desnoyers@efficios.com> wrote:

> > instead of bringing in yet another library which is a IIRC a 
> > distant copy of the kernel code to begin with.
> 
> This is either a lie, or immensely misinformed. You should go and 
> look at the source before doing nonsensical assumptions like this. 
> What you are saying cannot be further from the truth.

I was merely immensely misinformed, which (distinct!) possibility i 
tried to signal via the 'IIRC' qualifier as well ;-)

While right now i cannot clone the repository itself:

  $ git clone git://git.lttng.org/urcu
  Cloning into urcu...
  fatal: The remote end hung up unexpectedly

(tried it several times today, same failure)

I found a tarball of the package so could have a look again.

Despite my initial impression of it being kernel RCU code related (it 
has system.h, smp_mb, list_head, etc.), a closer look indeed suggests 
that the RCU implementation itself does not use the kernel RCU 
concepts so it sadly cannot be a distant copy of the kernel RCU code!

Which is too bad IMO: i don't think user-space RCU should necessarily 
be so different from kernel-space RCU. I think the two codebases 
could be shared, or at least they could become closer relatives! :-)

That could be done using the migration event notification trick i 
suggested in the previous mail.

Thanks,

	Ingo