Re: [PATCH] fix vmstat per cpu usage

From: Paul Mackerras
Date: Tue Aug 01 2006 - 18:42:35 EST

Andrew Morton writes:

> On Tue, 1 Aug 2006 19:36:21 +0200
> Jan Blunck <jblunck@xxxxxxx> wrote:
> > The per cpu variables are used incorrectly in vmstat.h.
> > - __get_cpu_var(vm_event_states.event[item])++;
> > + __get_cpu_var(vm_event_states).event[item]++;
> > }
> How odd. Are there any negative consequences to the existing code?

That sort of thing - i.e. using __get_cpu_var on something which isn't
just a simple variable name - works with the current per-cpu macro
definitions, because they are pretty simple, but one can imagine other
reasonable implementations of __get_cpu_var which need the argument to
be a simple variable name. I struck this when I was experimenting
with using __thread variables for per-cpu data.

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