panic on shutdown

[Nate Lawson]

John Baldwin wrote:
> On Thursday 02 September 2004 11:51 pm, Maxim Maximov wrote:
> 
>>Hello.
>>
>>	I just got this panic on shutdown using Power button, hand transcribed:
>>
>>Syncing disks: <numbers>
>>No buffers busy after final sync
>>Uptime: 21m53s
>>Powering system off using ACPI
>>
>>panic: lock (sleep mutex) Giant not locked @
>>/usr/src/sys/kern/kern_timeout.c:279
>>
>>cpuid = 0
>>KDB: enter: panic
>>ACPI power-off failed - timeout
>>
>>Rebooting...
>>cpu_reset: called on cpu#1
>>cpu_reset: Stopping other CPUs
>>
>>Here it hung until I pressed Power button again. Then it shut down.
> 
> Looks like the timeout/callout routine dropped Giant more than it acquired it.

I don't see how this could be triggered by ACPI.  If you reboot the 
system with ACPI disabled (or enabled), do you also get this message? 
We don't acquire or release Giant explicitly and the device and 
interrupt are both marked MPSAFE.  Well, we use Giant for busdma to set 
up the 1 MB trampoline in low memory for resume but that shouldn't 
affect this unless there's a bug in busdma.

BTW, why doesn't "panic" from the debugger prompt actually reset the 
system any more?

-Nate