Re: [LTP] [PATCH] fix endless loop hit messages for kdump test case.

[Subrata M. <su...@li...>]

This has been Applied to. Thanks.
--Subrata

On Tue, 2007-10-30 at 15:09 +0800, Cai Qian wrote:
> Hi,
> 
> In regards to the ltp-kdump issue where we see endless "loop hit"
> messages, 
> 
> NMI Watchdog detected LOCKUP on CPU 1
> lkdtm : Crash point INT_HARDWARE_ENTRY of type LOOP hit
> lkdtm : Crash point INT_HARDWARE_ENTRY of type LOOP hit
> lkdtm : Crash point INT_HARDWARE_ENTRY of type LOOP hit
> lkdtm : Crash point INT_HARDWARE_ENTRY of type LOOP hit
> lkdtm : Crash point INT_HARDWARE_ENTRY of type LOOP hit
> lkdtm : Crash point INT_HARDWARE_ENTRY of type LOOP hit
> lkdtm : Crash point INT_HARDWARE_ENTRY of type LOOP hit
> lkdtm : Crash point INT_HARDWARE_ENTRY of type LOOP hit
> ...
> 
> The following patch from Don Zickus will fix the issue.  Not sure if it
> is correct with regards to intention of the design, but nonetheless it
> gets the test by.
> 
> The reason for the problem seems to stem from the fact there are lots of
> irqs going on so when the test performs the correct NMI call, executing
> crash_kexec takes forever because interrupts are still happening on
> other cpus.  The patch just squashes the printks once count falls below
> zero.
> 
> This allows the code path to continue at an somewhat sane pace. I'm not
> entirely sure why after 5 hours the kdump code couldn't execute (despite
> the numerous printks for every interrupt).
> 
> Regards,
> CQ
> 
> diff -u testcases/kdump/rhtools/lkdtm_mod/lkdtm.c.orig
> testcases/kdump/rhtools/lkdtm_mod/lkdtm.c
> --- testcases/kdump/rhtools/lkdtm_mod/lkdtm.c.orig      2007-10-30 15:04:15.000000000 +0800
> +++ testcases/kdump/rhtools/lkdtm_mod/lkdtm.c   2007-10-30 15:06:44.000000000 +0800
> @@ -235,6 +235,9 @@
> 
>  void lkdtm_handler(void)
>  {
> +       if (count < 0)
> +               return;
> +
>         printk(KERN_INFO "lkdtm : Crash point %s of type %s hit\n",
>                                          cpoint_name, cpoint_type);
>         --count;
> 
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