Re: funny kernel death with ksoftirqd_CPUX taking up almost 100% of cpu?

I just experienced an alarming form of kernel death running a self compiled
SMP kernel with HIGHMEM enabled on my dual G4 -1gig machine.

The kernel tree used is Ben's 2.4.19-pre10 one rebuilt for SMP support, aec
IDE driver and otherwise basically stock.

I was debugging in gdb a large program and noticed typing got slower and
slower.  I quick check of top showed that ksoftirqd_CPU was taking up
almost 100% of the cpu.  I exited out of gdb and killed every process I
could think of but the usage of that kernel demaon stayed at near 100%.

It became so bad I could barely perform a straight shutdown (I had to hit
return numerous times to allow the other cpu to get some time to handle
the shutdown.

There were lots of messages like the following as I tried to shutdown:

../..

Jul 10 11:57:36 localhost kernel: wait_on_irq, CPU 0:
Jul 10 11:57:36 localhost kernel: irq:  -1 [0 0]
Jul 10 11:57:36 localhost kernel: bh:   0 [0 0]
Jul 10 11:57:37 localhost kernel:

Hrm... looks bad. global_irq_count got negative !

So either somebody is doing a mismatched hardirq_enter/leave
pair, which I seriously doubt, or our atomics are broken on
those machines (ugh !!!)

Paul, any good idea at hand ?

Ben.


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