Messages in this thread | | | Date | Fri, 12 Nov 2010 10:34:53 -0600 | From | Jason Wessel <> | Subject | Re: [V2 PATCH 0/6] x86, NMI: give NMI handler a face-lift |
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On 11/12/2010 10:11 AM, Don Zickus wrote: > On Fri, Nov 12, 2010 at 09:55:53AM -0600, Jason Wessel wrote: > >>> To answer your question, I doubt this patch series will change that >>> outcome if it is still broken. >>> >>> >>> >> It was most definitely broken in 2.6.36->2.6.37-rc1. Randy Dunlap had >> pointed this out in a separate exchange that was not on LKML. >> > > Can you clarify by what you mean by broken above? Was 2.6.36 good or bad? > >
It was absolutely broken in 2.6.36 which I believe is where the new LOCKUP_DETECTOR changes were introduced.
I tested 2.6.35 and it does not hard hang, but suffered from a different problem with a perf API change. The kgdb tests appear to loop and loop emitting endless streams of output in 2.6.35 and I already have that problem patched.
At this point we have to get back to a working base line. At this point if you use 2.6.37-rc1 the last remaining problem is the perf + lockup detector callback eating the injected DIE_NMI event which is meant to enter the debugger.
>> The symptom you would see looks like: >> >> ...kernel boot... >> Serial: 8250/16550 driver, 4 ports, IRQ sharing disabled >> serial8250: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A >> 00:06: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A >> brd: module loaded >> kgdb: Registered I/O driver kgdbts. >> kgdbts:RUN plant and detach test >> [...HARD HANG STARTS HERE...] >> >> The kernel is looping at that point waiting for the master kgdb cpu to >> have all the slaves join the debugger but it never happens because the >> perf callback chain which is used by the lockup detector eats the NMI >> IPI event. After the perf callback is processed perf returns >> NOTIFY_STOP so the notifier which brings the slave CPU into the debugger >> never fires. >> > > Ok. We have code to handle extra spurious NMIs that is hard to accurately > determine if the NMI was for perf or someone else. This logic may still > need tweaking. What cpu are you running on? AMD/Intel? If Intel, then > core/core2/nehalem? > >
In this case I just built a 32 bit kernel and ran it under kvm on a 64 bit host. I can send you the .config separately.
kvm -nographic -k en-us -kernel arch/x86/boot/bzImage -net user -net nic,macaddr=52:54:00:12:34:56,model=i82557b -append "console=ttyS0,115200 ip=dhcp root=/dev/nfs nfsroot=10.0.2.2:/space/exp/x86 rw acpi=force UMA=1" -smp 2
Thanks, Jason.
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