[PROBLEM] Soft lockup on Linux 2.6.27, 2 patches, Cell/PPC64

[Geert Uytterhoeven]

On Wed, 15 Oct 2008, Benjamin Herrenschmidt wrote:
> On Tue, 2008-10-14 at 11:32 +0200, Geert Uytterhoeven wrote:
> > which points again to smp_call_function_single...
> 
> Yup, it doesn't bring more information. At this stage, your 'other' CPU
> is stuck with interrupts disabled. Hard to tell what's happening without
> some HW assist. Do you have ways to trigger a non-maskable interrupt
> such as a 0x100 ? That would allow to catch the other guy in xmon and
> see what it was doing...

Interrupts are not disabled on the other CPU thread, at least not according to
the irqs_disabled() check I added to the printing of the `spinlock lockup'
message in __spin_lock_debug().

As the log also said

| hardirqs last  enabled at (5018779): [<c000000000007c1c>] restore+0x1c/0xe4
| hardirqs last disabled at (5018780): [<c000000000003600>] decrementer_common+0x100/0x180

I started blinking the LEDs on decrementer interupts, which do arrive on both
CPU threads.

However, I'm a bit puzzled by these `hardirqs last enabled/disabled' messages,
as they do indicate interrupts are off...

> It could be something in the ps3vram driver causing the kernel to
> lockup.... Now the question is whether the kernel is stuffed with
> something like a deadlock with interrupts off, or is it a HW problem
> causing a CPU to lockup on an access to the vram ?

It's not related to the ps3vram driver, as it happens without, too.

With kind regards,

Geert Uytterhoeven
Software Architect

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