[PATCH] D21733: [tsan] Treat non-barrier OSAtomic* functions as barriers to avoid false positives

[Kuba Brecka via llvm-commits]

kubabrecka created this revision.
kubabrecka added reviewers: dvyukov, kcc, glider.
kubabrecka added subscribers: llvm-commits, zaks.anna, dcoughlin.
kubabrecka added a project: Sanitizers.
Herald added a subscriber: kubabrecka.

The non-barrier versions of OSAtomic* functions are semantically mo_relaxed, but the two variants (e.g. OSAtomicAdd32 and OSAtomicAdd32Barrier) are actually aliases of each other, and we cannot have different interceptors for them, because they're actually the same function.  Thus, we have to stay conservative and treat the non-barrier versions as mo_acq_rel.


http://reviews.llvm.org/D21733

Files:
  lib/tsan/rtl/tsan_interceptors_mac.cc

Index: lib/tsan/rtl/tsan_interceptors_mac.cc
===================================================================
--- lib/tsan/rtl/tsan_interceptors_mac.cc
+++ lib/tsan/rtl/tsan_interceptors_mac.cc
@@ -27,6 +27,14 @@
 
 namespace __tsan {
 
+// The non-barrier versions of OSAtomic* functions are semantically mo_relaxed,
+// but the two variants (e.g. OSAtomicAdd32 and OSAtomicAdd32Barrier) are
+// actually aliases of each other, and we cannot have different interceptors for
+// them, because they're actually the same function.  Thus, we have to stay
+// conservative and treat the non-barrier versions as mo_acq_rel.
+#define ORDER_BARRIER mo_acq_rel
+#define ORDER_NONBARRIER mo_acq_rel
+
 #define OSATOMIC_INTERCEPTOR(return_t, t, tsan_t, f, tsan_atomic_f, mo) \
   TSAN_INTERCEPTOR(return_t, f, t x, volatile t *ptr) {                 \
     SCOPED_TSAN_INTERCEPTOR(f, x, ptr);                                 \
@@ -53,23 +61,24 @@
   }
 
 #define OSATOMIC_INTERCEPTORS_ARITHMETIC(f, tsan_atomic_f, m)                  \
-  m(int32_t, int32_t, a32, f##32, __tsan_atomic32_##tsan_atomic_f, mo_relaxed) \
+  m(int32_t, int32_t, a32, f##32, __tsan_atomic32_##tsan_atomic_f,             \
+    ORDER_NONBARRIER)                                                          \
   m(int32_t, int32_t, a32, f##32##Barrier, __tsan_atomic32_##tsan_atomic_f,    \
-    mo_acq_rel)                                                                \
+    ORDER_BARRIER)                                                             \
   m(int64_t, int64_t, a64, f##64, __tsan_atomic64_##tsan_atomic_f,             \
-    mo_relaxed)                                                                \
+    ORDER_NONBARRIER)                                                          \
   m(int64_t, int64_t, a64, f##64##Barrier, __tsan_atomic64_##tsan_atomic_f,    \
-    mo_acq_rel)
+    ORDER_BARRIER)
 
 #define OSATOMIC_INTERCEPTORS_BITWISE(f, tsan_atomic_f, m, m_orig)             \
   m(int32_t, uint32_t, a32, f##32, __tsan_atomic32_##tsan_atomic_f,            \
-    mo_relaxed)                                                                \
+    ORDER_NONBARRIER)                                                          \
   m(int32_t, uint32_t, a32, f##32##Barrier, __tsan_atomic32_##tsan_atomic_f,   \
-    mo_acq_rel)                                                                \
+    ORDER_BARRIER)                                                             \
   m_orig(int32_t, uint32_t, a32, f##32##Orig, __tsan_atomic32_##tsan_atomic_f, \
-    mo_relaxed)                                                                \
+    ORDER_NONBARRIER)                                                          \
   m_orig(int32_t, uint32_t, a32, f##32##OrigBarrier,                           \
-    __tsan_atomic32_##tsan_atomic_f, mo_acq_rel)
+    __tsan_atomic32_##tsan_atomic_f, ORDER_BARRIER)
 
 OSATOMIC_INTERCEPTORS_ARITHMETIC(OSAtomicAdd, fetch_add,
                                  OSATOMIC_INTERCEPTOR_PLUS_X)
@@ -88,16 +97,16 @@
   TSAN_INTERCEPTOR(bool, f, t old_value, t new_value, t volatile *ptr) {    \
     SCOPED_TSAN_INTERCEPTOR(f, old_value, new_value, ptr);                  \
     return tsan_atomic_f##_compare_exchange_strong(                         \
-        (tsan_t *)ptr, (tsan_t *)&old_value, (tsan_t)new_value, mo_relaxed, \
-        mo_relaxed);                                                        \
+        (tsan_t *)ptr, (tsan_t *)&old_value, (tsan_t)new_value,             \
+        ORDER_NONBARRIER, ORDER_NONBARRIER);                                \
   }                                                                         \
                                                                             \
   TSAN_INTERCEPTOR(bool, f##Barrier, t old_value, t new_value,              \
                    t volatile *ptr) {                                       \
     SCOPED_TSAN_INTERCEPTOR(f##Barrier, old_value, new_value, ptr);         \
     return tsan_atomic_f##_compare_exchange_strong(                         \
-        (tsan_t *)ptr, (tsan_t *)&old_value, (tsan_t)new_value, mo_acq_rel, \
-        mo_relaxed);                                                        \
+        (tsan_t *)ptr, (tsan_t *)&old_value, (tsan_t)new_value,             \
+        ORDER_BARRIER, ORDER_NONBARRIER);                                   \
   }
 
 OSATOMIC_INTERCEPTORS_CAS(OSAtomicCompareAndSwapInt, __tsan_atomic32, a32, int)
@@ -120,9 +129,9 @@
     return orig_byte & mask;                                  \
   }
 
-#define OSATOMIC_INTERCEPTORS_BITOP(f, op, m)      \
-  OSATOMIC_INTERCEPTOR_BITOP(f, op, m, mo_relaxed) \
-  OSATOMIC_INTERCEPTOR_BITOP(f##Barrier, op, m, mo_acq_rel)
+#define OSATOMIC_INTERCEPTORS_BITOP(f, op, m)                  \
+  OSATOMIC_INTERCEPTOR_BITOP(f, op, m, ORDER_NONBARRIER)       \
+  OSATOMIC_INTERCEPTOR_BITOP(f##Barrier, op, m, ORDER_BARRIER)
 
 OSATOMIC_INTERCEPTORS_BITOP(OSAtomicTestAndSet, __tsan_atomic8_fetch_or,
                             0x80u >> bit_index)


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