cvs commit: src/sys/i386/i386 vm_machdep.c

[Scott Long]

Nate Lawson wrote:
> John Baldwin wrote:
> 
>> On Tuesday 14 December 2004 03:11 pm, Nate Lawson wrote:
>>
>>> John Baldwin wrote:
>>>
>>>> On Tuesday 30 November 2004 01:18 am, Nate Lawson wrote:
>>>>
>>>>> njl         2004-11-30 06:18:46 UTC
>>>>>
>>>>> FreeBSD src repository
>>>>>
>>>>> Modified files:
>>>>>   sys/i386/i386        vm_machdep.c
>>>>> Log:
>>>>> MFamd64:  Remove the cpu_reset_proxy cruft now that we run boot() on
>>>>> cpu 0.  Also, restructure cpu_reset to be cleaner (no functional
>>>>> change.)
>>>>
>>>>
>>>> FYI, this breaks the 'reset' command from ddb if you panic on a cpu 
>>>> other
>>>> than the BSP.  boot() isn't the only function that calls 
>>>> cpu_reset(), so
>>>> perhaps this should be reverted (same for amd64)
>>>
>>>
>>> No, I think we should move forward instead of backward.  Entering the
>>> debugger should happen on the BSP and possibly other cpus need to be
>>> stopped by panic().
>>
>>
>> Erm, well, that's not always easy since sometimes when you panic you 
>> can't talk to the other CPUs for whatever reason.  Putting back the 
>> proxy reset doesn't hurt for now but does restore functionality in at 
>> least some cases.  I'd rather have that then certain hard panics not 
>> get into ddb because we couldn't get onto the BSP to run ddb.
> 
> 
> Perhaps you could give me some pointers on what is counted on to be 
> working when panic() is called?  I can't come up with a situation where 
> the proxy code couldn't be used upon entry to ddb.  If there were any 
> cases like this, the proxy code wouldn't work for cpu_reset() either. 
> Also, in such a case, it's hard to see how ddb could be usable since it 
> tries to stop other processors, which requires similar code to the proxy.
> 
> Or in other words, if you have enough capability to call panic() or 
> break to ddb, then you have enough resources to do an IPI and get onto 
> the BSP.
> 

Doing an IPI is useless if interrupts are disabled on the BSP for
whatever reason.  Now, if you want to send an NMI, that might be
interesting.

Scott