Messages in this thread | | | Date | Sat, 15 Dec 2007 19:43:28 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH 3/3] [UDP6]: Counter increment on BH mode |
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* Herbert Xu <herbert@gondor.apana.org.au> wrote:
> Ob Tue, Dec 04, 2007 at 12:17:23AM +1100, Herbert Xu wrote: > > > > Never mind, we already have that in local_t and as Alexey correctly > > points out, USER is still going to be the expensive variant with the > > preempt_disable (well until BH gets threaded). So how about this patch? > > I didn't hear any objections so here is the patch again. > > [SNMP]: Fix SNMP counters with PREEMPT > > The SNMP macros use raw_smp_processor_id() in process context which is > illegal because the process may be preempted and then migrated to > another CPU.
nit: please use 'invalid' instead of 'illegal'.
> This patch makes it use get_cpu/put_cpu to disable preemption. > > Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
> - (per_cpu_ptr(mib[1], raw_smp_processor_id())->mibs[field]++) > + do { \ > + per_cpu_ptr(mib[1], get_cpu())->mibs[field]++; \ > + put_cpu(); \ > + } while (0)
> - (per_cpu_ptr(mib[1], raw_smp_processor_id())->mibs[field] += addend) > + do { \ > + per_cpu_ptr(mib[1], get_cpu())->mibs[field] += addend; \ > + put_cpu(); \ > + } while (0)
we could perhaps introduce stat_smp_processor_id(), which signals that the CPU id is used for statistical purposes and does not have to be exact? In any case, your patch looks good too.
Ingo
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