Re: x86_64 2.6.35.* kernels and Intel Xeon X5550

[Marc Aurele La France <tsi@ualberta.ca>]

On Thu, 7 Oct 2010, Marc Aurele La France wrote:

> I administer a cluster composed of a mixture of various Opteron models and 
> Intel Xeon X5550's.  The 2.6.34.*, and prior, kernels run fine on all of 
> them.  The 2.6.35 series also runs fine on the Opterons, but not on the 
> Xeon's.  All of these are CONFIG_GENERIC_CPU kernels.

> On the Xeon's, 2.6.35 hangs early on, upon the first test of trace events 
> (in kernel/trace/trace_events.c:event_trace_self_tests()).  When disabling 
> all tracing, debugging, etc., it still hangs but slightly later.  The 
> megaraid_sas module is loaded, detects the adapter, but never gets around to 
> registering it with the SCSI layer.

> Core2-specific kernels also hang the same way, as do UP kernels.  I've tried 
> backing out certain commits that seemed likely candidates, but have yet to 
> stumble upon the one (or more) that is causing this.

> Does anyone have any ideas?

This is due to "CONFIG_INTEL_IDLE=y".  "m" or "n", the hang doesn't occur.

Of the kernels I've tested, INTEL_IDLE first appears in 2.6.34-git15.  So, 
technically, this is not a regression against 2.6.34.

This does, however, amount to a vote of non-confidence against intel_idle.c.

Marc.

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