Re: Is it possible to implement interrupt time printk's reliably?

[Jon Smirl]

--- Andrew Morton <akpm@xxxxxxxx> wrote:
> Jon Smirl <jonsmirl@xxxxxxxxx> wrote:
> >
> > Problem:
> >  1) Some operations on graphics cards cannot be stopped once they are
> started.
> >  It's not reasonable to turn interrupts off around these operations.
> >  2) Kernel developers want console printk's to work from interrupt routines.
> > 
> >  How do you fix this situation?
> 
> Really you should use spin_lock_irqsave() on some driver-private lock
> around the operation.  Why is it not reasonable to disable irq's? 
> Duration, presumably?

The operations take a while and would ruin latency. You might be copying 8MB of
data.

> If you're in process context you can use acquire_console_sem(), which will
> serialise against printk.
> 

Won't I deadlock if I have acquire_console_sem(), take an interrupt, and then a
printk is issued from the interrupt handelr?


=====
Jon Smirl
jonsmirl@xxxxxxxxx


	
		
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