[SNMP]: Fix SNMP counters with PREEMPT

[Herbert Xu <herbert@gondor.apana.org.au>]

On Sat, Dec 15, 2007 at 06:03:19PM +0100, Eric Dumazet wrote:
>
> How come you change SNMP_INC_STATS_USER() but not SNMP_INC_STATS() ?

Heh, my brain must have blocked me from seeing it because it's
too hard :)

Let's fix it the stupid way first and I'll do a local_t conversion
later.

[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.

This patch makes it use get_cpu/put_cpu to disable preemption.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Thanks,
-- 
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Email: Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
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--
diff --git a/include/net/snmp.h b/include/net/snmp.h
index 9c5793d..fbb6666 100644
--- a/include/net/snmp.h
+++ b/include/net/snmp.h
@@ -23,6 +23,7 @@
 
 #include <linux/cache.h>
 #include <linux/snmp.h>
+#include <linux/smp.h>
 
 /*
  * Mibs are stored in array of unsigned long.
@@ -135,14 +136,26 @@ struct linux_mib {
 #define SNMP_INC_STATS_BH(mib, field) 	\
 	(per_cpu_ptr(mib[0], raw_smp_processor_id())->mibs[field]++)
 #define SNMP_INC_STATS_USER(mib, field) \
-	(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)
 #define SNMP_INC_STATS(mib, field) 	\
-	(per_cpu_ptr(mib[!in_softirq()], raw_smp_processor_id())->mibs[field]++)
+	do { \
+		per_cpu_ptr(mib[!in_softirq()], get_cpu())->mibs[field]++; \
+		put_cpu(); \
+	} while (0)
 #define SNMP_DEC_STATS(mib, field) 	\
-	(per_cpu_ptr(mib[!in_softirq()], raw_smp_processor_id())->mibs[field]--)
+	do { \
+		per_cpu_ptr(mib[!in_softirq()], get_cpu())->mibs[field]--; \
+		put_cpu(); \
+	} while (0)
 #define SNMP_ADD_STATS_BH(mib, field, addend) 	\
 	(per_cpu_ptr(mib[0], raw_smp_processor_id())->mibs[field] += addend)
 #define SNMP_ADD_STATS_USER(mib, field, addend) 	\
-	(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)
 
 #endif
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