Re: [PATCH] hangcheck-timer is broken on x86

Andrew Morton
2010-03-26T21:24:37Z

On Tue, 23 Mar 2010 23:36:11 -0400
Yury Polyanskiy <ypolyans@princeton.edu> wrote:

> The drivers/char/hangcheck-timer.c is doubly broken. First, the
> following line overflows unsigned long:
> # define TIMER_FREQ (HZ*loops_per_jiffy)
>
> Second, and more importantly, loops_per_jiffy has little to do with the conversion from the
> the time scale of get_cycles() (aka rdtsc) to the time scale of jiffies.

It's a bit odd to have a driver be this broken on x86_32 for five years
without anyone noticing. What are the user-visible effects of these
shortcomings?

Also, please do send us a Signed-off-by: for this patch, as explained
in Documentation/SubmittingPatches, thanks.