Hi Ondřej,
I have two questions:
1. I've tried to help TSAN by replacing the custom atomics with __atomic gcc
primitives - that seems to work pretty well. Note that using C11 stdatomics
is frankly not possible here because it would require wrapping everything
into
_Atomic().
I'm using the attached patch which does much the same.
Ciao, Duncan.
diff --git a/External/UserspaceRCU/userspace-rcu/include/urcu/system.h b/External/UserspaceRCU/userspace-rcu/include/urcu/system.h
index faae390554..82898d1dbe 100644
--- a/External/UserspaceRCU/userspace-rcu/include/urcu/system.h
+++ b/External/UserspaceRCU/userspace-rcu/include/urcu/system.h
@@ -26,34 +26,45 @@
* Identify a shared load. A cmm_smp_rmc() or cmm_smp_mc() should come
* before the load.
*/
-#define _CMM_LOAD_SHARED(p) CMM_ACCESS_ONCE(p)
+#define _CMM_LOAD_SHARED(p) \
+ __extension__ \
+ ({ \
+ __typeof__(p) v; \
+ __atomic_load(&p, &v, __ATOMIC_RELAXED); \
+ v; \
+ })
/*
* Load a data from shared memory, doing a cache flush if required.
*/
-#define CMM_LOAD_SHARED(p) \
- __extension__ \
- ({ \
- cmm_smp_rmc(); \
- _CMM_LOAD_SHARED(p); \
+#define CMM_LOAD_SHARED(p) \
+ __extension__ \
+ ({ \
+ __typeof__(p) v; \
+ __atomic_load(&p, &v, __ATOMIC_ACQUIRE); \
+ v; \
})
/*
* Identify a shared store. A cmm_smp_wmc() or cmm_smp_mc() should
* follow the store.
*/
-#define _CMM_STORE_SHARED(x, v) __extension__ ({ CMM_ACCESS_ONCE(x) = (v); })
+#define _CMM_STORE_SHARED(x, v) \
+ __extension__ \
+ ({ \
+ __typeof__(x) w = v; \
+ __atomic_store(&x, &w, __ATOMIC_RELAXED); \
+ })
/*
* Store v into x, where x is located in shared memory. Performs the
* required cache flush after writing. Returns v.
*/
-#define CMM_STORE_SHARED(x, v) \
- __extension__ \
- ({ \
- __typeof__(x) _v = _CMM_STORE_SHARED(x, v); \
- cmm_smp_wmc(); \
- _v = _v; /* Work around clang "unused result" */ \
+#define CMM_STORE_SHARED(x, v) \
+ __extension__ \
+ ({ \
+ __typeof__(x) w = v; \
+ __atomic_store(&x, &w, __ATOMIC_RELEASE); \
})
#endif /* _URCU_SYSTEM_H */
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