percpu: add __percpu sparse annotations to net

Add __percpu sparse annotations to net.

These annotations are to make sparse consider percpu variables to be
in a different address space and warn if accessed without going
through percpu accessors.  This patch doesn't affect normal builds.

The macro and type tricks around snmp stats make things a bit
interesting.  DEFINE/DECLARE_SNMP_STAT() macros mark the target field
as __percpu and SNMP_UPD_PO_STATS() macro is updated accordingly.  All
snmp_mib_*() users which used to cast the argument to (void **) are
updated to cast it to (void __percpu **).

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: David S. Miller <davem@davemloft.net>
Cc: Patrick McHardy <kaber@trash.net>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Vlad Yasevich <vladislav.yasevich@hp.com>
Cc: netdev@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 8 insertions, 4 deletions

diff --git a/include/net/snmp.h b/include/net/snmp.h
index da02ee027d69..692ee0061dc4 100644
--- a/include/net/snmp.h
+++ b/include/net/snmp.h
@@ -129,9 +129,9 @@ struct linux_xfrm_mib {
  * nonlocked_atomic_inc() primitives -AK
  */ 
 #define DEFINE_SNMP_STAT(type, name)    \
-        __typeof__(type) *name[2]
+        __typeof__(type) __percpu *name[2]
 #define DECLARE_SNMP_STAT(type, name)   \
-        extern __typeof__(type) *name[2]
+        extern __typeof__(type) __percpu *name[2]
 
 #define SNMP_STAT_BHPTR(name)   (name[0])
 #define SNMP_STAT_USRPTR(name)  (name[1])
@@ -148,9 +148,13 @@ struct linux_xfrm_mib {
                         __this_cpu_add(mib[0]->mibs[field], addend)
 #define SNMP_ADD_STATS_USER(mib, field, addend) \
                         this_cpu_add(mib[1]->mibs[field], addend)
+/*
+ * Use "__typeof__(*mib[0]) *ptr" instead of "__typeof__(mib[0]) ptr"
+ * to make @ptr a non-percpu pointer.
+ */
 #define SNMP_UPD_PO_STATS(mib, basefield, addend)       \
         do { \
-                __typeof__(mib[0]) ptr; \
+                __typeof__(*mib[0]) *ptr; \
                 preempt_disable(); \
                 ptr = this_cpu_ptr((mib)[!in_softirq()]); \
                 ptr->mibs[basefield##PKTS]++; \
@@ -159,7 +163,7 @@ struct linux_xfrm_mib {
         } while (0)
 #define SNMP_UPD_PO_STATS_BH(mib, basefield, addend)    \
         do { \
-                __typeof__(mib[0]) ptr = \
+                __typeof__(*mib[0]) *ptr = \
                         __this_cpu_ptr((mib)[!in_softirq()]); \
                 ptr->mibs[basefield##PKTS]++; \
                 ptr->mibs[basefield##OCTETS] += addend;\