consistent hard lockup with recent kernels

[Daniel Eriksson]

Jon Noack wrote:

> Yeah, it is most likely bugs uncovered by native preemption.  For now 
> you can remask then by commenting out the "#define PREEMPTION" in 
> src/sys/<ARCH>/include/param.h and rebuilding your kernel.  Robert 
> Watson's comments on this:
> "This results in a quite usable kernel, although quite probably more 
> poor interrupt handling latency, etc."

I just tried a new kernel (2004.07.16.01.00.00) with preemption turned on,
and my problems with interrupt storms and SATA still remains. With
preemption turned off the machine seems stable, but somewhat sluggish.

With preemption enabled I get interrupt storms and DMA problems with the
SATA devices like below when trying to access all discs at once (running
fsck on all 11 file systems simultaneously). ad20 is one of two SATA devices
in the system.

Interrupt storm detected on "irq20: atapci4"; throttling interrupt source
ad20: FAILURE - already active DMA on this device
ad20: setting up DMA failed

Attached is the dmesg.boot from the old kernel (2004.07.12.22.00.00) with
preemption turned off that seems to be stable.

I'm using HZ=2000, DEVICE_POLLING and ZERO_COPY_SOCKETS, plus device apic. I
also have net.isr enabled.

'vmstat -i' gives the following output:
interrupt                          total       rate
irq1: atkbd0                         248          0
irq0: clk                        8176853       1993
irq4: sio0                            12          0
irq6: fdc0                             6          0
irq8: rtc                         524902        127
irq13: npx0                            1          0
irq14: ata0                        33148          8
irq15: ata1                        24641          6
irq16: atapci0+                   867398        211
irq17: atapci2+                   296877         72
irq18: re0                             2          0
irq19: ahc0                        94035         22
irq20: atapci4                    184381         44
irq23: vr0                             2          0
Total                           10202506       2487

/Daniel Eriksson
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