aboutsummaryrefslogtreecommitdiffstats
path: root/include/linux/rcupdate.h
diff options
context:
space:
mode:
authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2010-04-30 06:42:01 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2010-06-14 16:37:26 -0700
commitf5155b33277c9678041a27869165619bb34f722f (patch)
tree16cef227f7e05e3b8d97a68d7b7a60e86255cb98 /include/linux/rcupdate.h
parent551d55a944b143ef26fbd482d1c463199d6f65cf (diff)
downloadmrst-s0i3-test-f5155b33277c9678041a27869165619bb34f722f.tar.gz
mrst-s0i3-test-f5155b33277c9678041a27869165619bb34f722f.tar.xz
mrst-s0i3-test-f5155b33277c9678041a27869165619bb34f722f.zip
rcu: add an rcu_dereference_index_check()
The sparse RCU-pointer checking relies on type magic that dereferences the pointer in question. This does not work if the pointer is in fact an array index. This commit therefore supplies a new RCU API that omits the sparse checking to continue to support rcu_dereference() on integers. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'include/linux/rcupdate.h')
-rw-r--r--include/linux/rcupdate.h33
1 files changed, 33 insertions, 0 deletions
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 2b7fc506e47..9fbc54a2585 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -566,4 +566,37 @@ static inline void debug_rcu_head_unqueue(struct rcu_head *head)
}
#endif /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
+#ifndef CONFIG_PROVE_RCU
+#define __do_rcu_dereference_check(c) do { } while (0)
+#endif /* #ifdef CONFIG_PROVE_RCU */
+
+#define __rcu_dereference_index_check(p, c) \
+ ({ \
+ typeof(p) _________p1 = ACCESS_ONCE(p); \
+ __do_rcu_dereference_check(c); \
+ smp_read_barrier_depends(); \
+ (_________p1); \
+ })
+
+/**
+ * rcu_dereference_index_check() - rcu_dereference for indices with debug checking
+ * @p: The pointer to read, prior to dereferencing
+ * @c: The conditions under which the dereference will take place
+ *
+ * Similar to rcu_dereference_check(), but omits the sparse checking.
+ * This allows rcu_dereference_index_check() to be used on integers,
+ * which can then be used as array indices. Attempting to use
+ * rcu_dereference_check() on an integer will give compiler warnings
+ * because the sparse address-space mechanism relies on dereferencing
+ * the RCU-protected pointer. Dereferencing integers is not something
+ * that even gcc will put up with.
+ *
+ * Note that this function does not implicitly check for RCU read-side
+ * critical sections. If this function gains lots of uses, it might
+ * make sense to provide versions for each flavor of RCU, but it does
+ * not make sense as of early 2010.
+ */
+#define rcu_dereference_index_check(p, c) \
+ __rcu_dereference_index_check((p), (c))
+
#endif /* __LINUX_RCUPDATE_H */