Re: netpoll trapped question

[Jeff Moyer]

==> Regarding Re: netpoll trapped question; Matt Mackall <mpm@xxxxxxxxxxx> adds:

mpm> On Tue, Sep 07, 2004 at 12:53:17PM -0400, Jeff Moyer wrote: A random
mpm> lock private to a given driver, for instance one taken on entry to the
mpm> IRQ handler. If said driver tries to do a printk inside that lock and
mpm> we recursively call the handler in netconsole, we're in trouble.
mpm> These are the issues that will have to be cleaned up in individual
mpm> drivers. So far, I haven't seen any reports, but I'm pretty sure such
mpm> cases exist. I suppose it's also possible for us to disable recursion
mpm> in netconsole instead of at the netpoll level.
>> Recursion in netconsole is protected by the console semaphore.

mpm> Yes, true. But we're still in trouble if we have nic irq handler ->
mpm> take private lock -> printk -> netconsole -> nic irq handler -> take
mpm> private lock. See?

Okay, so that one has to be addressed on a per-driver basis.  There's no
way for us to detect that situation.  And how do drivers address this?
Simply don't printk inside the lock?  I think that's reasonable.

-Jeff
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