Messages in this thread | | | Date | Tue, 7 Sep 2004 12:22:12 -0500 | From | Matt Mackall <> | Subject | Re: netpoll trapped question |
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On Tue, Sep 07, 2004 at 01:10:00PM -0400, Jeff Moyer wrote: > ==> Regarding Re: netpoll trapped question; Matt Mackall <mpm@selenic.com> 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.
That or drop the lock where possible.
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