[Crash-utility] HZ undefined in libc headers

[Dave Anderson]

Olaf Hering wrote:

> Upcoming glibc header files have no visible definition of HZ anymore. A
> glibc macro exist to query the current tick rate. This macro will likely
> work for all other apps, Unfortunately crash wants to know the HZ value
> of the crashed kernel.
> My patch makes the assumption that the dump file is analyzed on a system
> similar to the crashed one. I dont know how accurate that is.
> If I read the source right, HZ is currently forced to be 1000 which is
> not true either. Newer kernels can be configured for 100, 250 and 1000.
>
> Ideally, the core file exports HZ in some way. I see cfq_slice_async is
> used to get the HZ value in task_init().

Hi Olaf,

Ok, what I'm doing is using Troy's IKCONFIG-read functionality to
get CONFIG_HZ if it's available -- and that gets done before any
of the machdep_init() calls.  If that fails (i.e., machdep->hz is still 0),
then all of the processor types will initialize machdep->hz in
the same way that they do now.  However, if HZ is not defined,
I've added this to defs.h:

#ifndef HZ
#define HZ sysconf(_SC_CLK_TCK)
#endif

So I believe this addresses all of our concerns for now.

Dave