#define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x))
/*
- * Load a data from remote memory, doing a cache flush if required.
+ * Identify a shared load. A smp_rmc() or smp_mc() should come before the load.
*/
-#define LOAD_REMOTE(p) ({ \
- smp_rmc(); \
- typeof(p) _________p1 = ACCESS_ONCE(p); \
- (_________p1); \
- })
+#define _LOAD_SHARED(p) ACCESS_ONCE(p)
/*
- * Store v into x, where x is located in remote memory. Performs the required
- * cache flush after writing.
+ * Load a data from shared memory, doing a cache flush if required.
+ */
+#define LOAD_SHARED(p) \
+ ({ \
+ smp_rmc(); \
+ _LOAD_SHARED(p); \
+ })
+
+
+/*
+ * Identify a shared store. A smp_wmc() or smp_mc() should follow the store.
*/
-#define STORE_REMOTE(x, v) \
+#define _STORE_SHARED(x, v) \
do { \
(x) = (v); \
- smp_wmc; \
+ } while (0)
+
+/*
+ * Store v into x, where x is located in shared memory. Performs the required
+ * cache flush after writing.
+ */
+#define STORE_SHARED(x, v) \
+ do { \
+ _STORE_SHARED(x, v); \
+ smp_wmc(); \
} while (0)
/**
*/
#define rcu_dereference(p) ({ \
- typeof(p) _________p1 = LOAD_REMOTE(p); \
+ typeof(p) _________p1 = LOAD_SHARED(p); \
smp_read_barrier_depends(); \
(_________p1); \
})
-
-
#define SIGURCU SIGUSR1
/*
* Make sure both tests below are done on the same version of *value
* to insure consistency.
*/
- v = LOAD_REMOTE(*value);
+ v = LOAD_SHARED(*value);
return (v & RCU_GP_CTR_NEST_MASK) &&
((v ^ urcu_gp_ctr) & RCU_GP_CTR_BIT);
}
/* urcu_gp_ctr = RCU_GP_COUNT | (~RCU_GP_CTR_BIT or RCU_GP_CTR_BIT) */
/*
* The data dependency "read urcu_gp_ctr, write urcu_active_readers",
- * serializes those two memory operations. We are not using STORE_REMOTE
- * and LOAD_REMOTE here (although we should) because the writer will
- * wake us up with a signal which does a flush in its handler to perform
- * urcu_gp_ctr re-read and urcu_active_readers commit to main memory.
+ * serializes those two memory operations. The memory barrier in the
+ * signal handler ensures we receive the proper memory commit barriers
+ * required by _STORE_SHARED and _LOAD_SHARED whenever communication
+ * with the writer is needed.
*/
if (likely(!(tmp & RCU_GP_CTR_NEST_MASK)))
- urcu_active_readers = ACCESS_ONCE(urcu_gp_ctr);
+ _STORE_SHARED(urcu_active_readers, _LOAD_SHARED(urcu_gp_ctr));
else
- urcu_active_readers = tmp + RCU_GP_COUNT;
+ _STORE_SHARED(urcu_active_readers, tmp + RCU_GP_COUNT);
/*
* Increment active readers count before accessing the pointer.
* See force_mb_all_threads().
* Finish using rcu before decrementing the pointer.
* See force_mb_all_threads().
*/
- urcu_active_readers -= RCU_GP_COUNT;
+ _STORE_SHARED(urcu_active_readers, urcu_active_readers - RCU_GP_COUNT);
}
/**
if (!__builtin_constant_p(v) || \
((v) != NULL)) \
wmb(); \
- (p) = (v); \
- smp_wmc(); \
+ STORE_SHARED(p, v); \
})
#define rcu_xchg_pointer(p, v) \