Re: [PATCH 01/12] libiscsi: Convert to host_lock less w/ interrupts disabled internally

Matthew Wilcox
2010-12-20T02:08:04Z

On Sun, Dec 19, 2010 at 05:22:06PM -0800, Nicholas A. Bellinger wrote:
> Actually sorry, Mike Christie did already make a clarification on this
> subject here:
>
> http://marc.info/?l=linux-scsi&m=129010439421506&w=2
>
> I had originally thought the same that session->lock should be using
> some flavour of spin_lock_irq*() as well, but apparently this is not the
> case for libiscsi.

Right, so it seems. "the session lock is just locked in softirqs/timers"
means that it does need to be the _bh() version of spin_lock though.

I'm actually not sure ... is it safe to use the _bh versions in BH
context? I think it is because the preempt count is nested, unlike the
_irq variants of spinlocks.

--
Matthew Wilcox Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours. We can't possibly take such
a retrograde step."