Messages in this thread | | | Date | Tue, 9 Jan 2007 13:01:10 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH] local_t : Documentation |
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On Mon, 8 Jan 2007 22:14:46 -0500 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> wrote:
> +* How to use local atomic operations > + > +#include <linux/percpu.h> > +#include <asm/local.h> > + > +static DEFINE_PER_CPU(local_t, counters) = LOCAL_INIT(0); > + > + > +* Counting > + > +In preemptible context, use get_cpu_var() and put_cpu_var() around local atomic > +operations : it makes sure that preemption is disabled around write access to > +the per cpu variable. For instance : > + > + local_inc(&get_cpu_var(counters)); > + put_cpu_var(counters);
Confused. The whole point behind local_t is that we can do atomic-wrt-interrupts inc and dec on them.
Consequently, as atomic-wrt-interrupts means atomic-wrt-preemption, there is no need to do a preempt_disable() around local_inc() and local_dec().
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