System freezes with SMP support enabled

[Terry Lambert]

John Baldwin wrote:
> > Second, it seems to me that there's a possibility for a deadlock
> > if an interrupt comes in on one CPU, and an ithread to handle it
> > is scheduled to run on a different CPU.  You may want to try using
> > SCHED_4BSD to see if that changes anything.
> 
> Huh?  Where in the code do you see this happening exactly?  All the
> bits you should need to look at for this are in ithread_schedule()
> and ithread_loop() in sys/kern/kern_intr.c.

Off-list, I have been helping someone debug an ithread_exit() bug,
after which they can submit the patches if they want.  I saw that
there might be an issue if affinity is applied to ithread scheduling,
if the interrupt is not routed to the CPU with the affinity.  THis
was a side issue, having nothing to do with the problem I was trying
to help debug at the time, but it tickled my suspic-o-meter.


> Not only that, but 4.8 doesn't have ithreads so I doubt seriously
> that this is causing the lockups on 4.x.

Yeah, my bad.  I was only considering the case of his complaint on
5.0, since he complained about both 5.0 and 4.8, and 5.0 last, so
that's what was in my recall buffer.  8-) 8-).

-- Terry