Re: [PATCH 0/2] [RFC] RT: Optionally allow IRQF_NODELAY on serial console

On Fri, 5 Oct 2007, Gregory Haskins wrote:
This series may help debugging certain circumstances where the serial
console is unreponsive (e.g. RT51+ spinner, or scheduler problem). It changes
the serial8250 driver to use IRQF_NODELAY so that interrupts execute in irq
context instead of a kthread.

It works pretty well on this end, though it is admitted not fully baked. For
instance, a few paths in sysrq can still call into non-raw spinlocks
(sched_debug_show, for instance) which will cause subsequent errors. Also,
if you use KDB, be sure to convert the kdb_printf_lock to raw as well. I may
send a KDB related patch seperately.

I am sending this out now in case it is helpful to someone.

The simple non-patch solution is to up the priority of the serial
console irq to maximum. That's usually sufficient to catch runnaway tasks
etc. It does not interfere with the system in normal operation as long as
you do not hit keys in your minicom.

I doubt that your patch has a chance to survive lockdep and anything which
is not a sysrq.

tglx
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