On Tue, Jun 14, 2011 at 1:12 AM, Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote:
>> transport_lookup_cmd_lun() may be called from interrupt context (eg
>> tcm_loop_allocate_core_cmd() calls it, and it has a comment that says,
>> "Can be called from interrupt context"), so it needs to use
>> spin_lock_irqsave() instead of spin_lock_irq() to avoid enabling
>> interrupts at the wrong time.
> It currently is, but I think we'd better be off stopping to call it from
> IRQ context. Soon after we offload the work to thread context anyway.
> By moving the point of offloading a little earlier we can simply the
> calling conventions a lot, and keep the amount of code that needs
> IRQ-safe locking minimal.
Fair enough... however that seems like a much more major project,
as eg the qla2xxx code does a fair bit from interrupt context.
Also it seems even if we are running from thread context it would
be legitimate for a target driver to do
spin_lock_irq(&internal_target_lock);
...
transport_lookup_cmd_lun();
...
spin_unlock_irq
and so transport_lookup_cmd_lun() shouldn't be reenabling IRQs
unconditionally.
Thanks,
Roland
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