[Crash-utility] Re: crash 4.0-8.9 w/ 2.6.30-rc6

[Mike Snitzer]

On Wed, May 27 2009 at  8:37am -0400,
Dave Anderson <anderson at redhat.com> wrote:

> 
> ----- "Mike Snitzer" <snitzer at redhat.com> wrote:
> 
> > Hi Dave,
> > 
> > crash is failing with the following when I try to throw a 2.6.30-rc6
> > vmcore at it:
> > 
> > crash: invalid structure size: x8664_pda
> >        FILE: x86_64.c  LINE: 584  FUNCTION: x86_64_cpu_pda_init()
> > 
> > [/usr/bin/crash] error trace: 449c7f => 4ce815 => 4d00cf => 50936d
> > 
> >   50936d: SIZE_verify+168
> >   4d00cf: (undetermined)
> >   4ce815: x86_64_init+3205
> >   449c7f: main_loop+152
> > 
> > I can dig deeper but your help would be very much appreciated.
> > 
> > Mike
> 
> The venerable "been-there-since-the-beginning-of-x86_64" x8664_pda
> data structure no longer exists.  It was a per-cpu array of a fundamental
> data structure that things like "current", the per-cpu magic number, the
> cpu number, the current kernel stack pointer, the per-cpu IRQ stack pointer,
> etc. all came from:  
> 
> /* Per processor datastructure. %gs points to it while the kernel runs */
> struct x8664_pda {
>         struct task_struct *pcurrent;   /* Current process */
>         unsigned long data_offset;      /* Per cpu data offset from linker address */
>         unsigned long kernelstack;  /* top of kernel stack for current */
>         unsigned long oldrsp;       /* user rsp for system call */
> #if DEBUG_STKSZ > EXCEPTION_STKSZ
>         unsigned long debugstack;   /* #DB/#BP stack. */
> #endif
>         int irqcount;               /* Irq nesting counter. Starts with -1 */
>         int cpunumber;              /* Logical CPU number */
>         char *irqstackptr;      /* top of irqstack */
>         int nodenumber;             /* number of current node */
>         unsigned int __softirq_pending;
>         unsigned int __nmi_count;       /* number of NMI on this CPUs */
>         int mmu_state;
>         struct mm_struct *active_mm;
>         unsigned apic_timer_irqs;
> } ____cacheline_aligned_in_smp;
> 
> There have been upstream rumblings about replacing it with a more efficient
> per-cpu implementation for some time now, but I haven't studied how the new
> scheme works yet.  It will be a major re-work for the crash utility, so you're
> pretty much out of luck for now.  (Try "gdb vmlinux vmcore" for basic info)

Ah OK.  I was just looking to get a stack trace.  Unfortunately gdb
isn't playing nice either:

(gdb) bt
#0  kstat_irqs_cpu (irq=<value optimized out>, cpu=2) at kernel/irq/handle.c:555
Cannot access memory at address 0xffff88007e5e7d50

> In the meantime, can you give me a copy of your vmcore?  (offline -- note that
> I'm forwarding this to the crash-utility mailing list).  And I'll start working
> on it.

OK, will do.

Mike