[compiler-rt] r273890 - [tsan] Treat non-barrier OSAtomic* functions as barriers to avoid false positives

[Kuba Brecka via llvm-commits]

Author: kuba.brecka
Date: Mon Jun 27 11:10:14 2016
New Revision: 273890

URL: http://llvm.org/viewvc/llvm-project?rev=273890&view=rev
Log:
[tsan] Treat non-barrier OSAtomic* functions as barriers to avoid false positives

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.

Differential Revision: http://reviews.llvm.org/D21733


Modified:
    compiler-rt/trunk/lib/tsan/rtl/tsan_interceptors_mac.cc

Modified: compiler-rt/trunk/lib/tsan/rtl/tsan_interceptors_mac.cc
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/tsan/rtl/tsan_interceptors_mac.cc?rev=273890&r1=273889&r2=273890&view=diff
==============================================================================
--- compiler-rt/trunk/lib/tsan/rtl/tsan_interceptors_mac.cc (original)
+++ compiler-rt/trunk/lib/tsan/rtl/tsan_interceptors_mac.cc Mon Jun 27 11:10:14 2016
@@ -27,6 +27,14 @@ typedef long long_t;  // NOLINT
 
 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.
+static const morder kMacOrderBarrier = mo_acq_rel;
+static const morder kMacOrderNonBarrier = 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 @@ namespace __tsan {
   }
 
 #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,             \
+    kMacOrderNonBarrier)                                                       \
   m(int32_t, int32_t, a32, f##32##Barrier, __tsan_atomic32_##tsan_atomic_f,    \
-    mo_acq_rel)                                                                \
+    kMacOrderBarrier)                                                          \
   m(int64_t, int64_t, a64, f##64, __tsan_atomic64_##tsan_atomic_f,             \
-    mo_relaxed)                                                                \
+    kMacOrderNonBarrier)                                                       \
   m(int64_t, int64_t, a64, f##64##Barrier, __tsan_atomic64_##tsan_atomic_f,    \
-    mo_acq_rel)
+    kMacOrderBarrier)
 
 #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)                                                                \
+    kMacOrderNonBarrier)                                                       \
   m(int32_t, uint32_t, a32, f##32##Barrier, __tsan_atomic32_##tsan_atomic_f,   \
-    mo_acq_rel)                                                                \
+    kMacOrderBarrier)                                                          \
   m_orig(int32_t, uint32_t, a32, f##32##Orig, __tsan_atomic32_##tsan_atomic_f, \
-    mo_relaxed)                                                                \
+    kMacOrderNonBarrier)                                                       \
   m_orig(int32_t, uint32_t, a32, f##32##OrigBarrier,                           \
-    __tsan_atomic32_##tsan_atomic_f, mo_acq_rel)
+    __tsan_atomic32_##tsan_atomic_f, kMacOrderBarrier)
 
 OSATOMIC_INTERCEPTORS_ARITHMETIC(OSAtomicAdd, fetch_add,
                                  OSATOMIC_INTERCEPTOR_PLUS_X)
@@ -88,16 +97,16 @@ OSATOMIC_INTERCEPTORS_BITWISE(OSAtomicXo
   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,             \
+        kMacOrderNonBarrier, kMacOrderNonBarrier);                          \
   }                                                                         \
                                                                             \
   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,             \
+        kMacOrderBarrier, kMacOrderNonBarrier);                             \
   }
 
 OSATOMIC_INTERCEPTORS_CAS(OSAtomicCompareAndSwapInt, __tsan_atomic32, a32, int)
@@ -120,9 +129,9 @@ OSATOMIC_INTERCEPTORS_CAS(OSAtomicCompar
     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, kMacOrderNonBarrier)       \
+  OSATOMIC_INTERCEPTOR_BITOP(f##Barrier, op, m, kMacOrderBarrier)
 
 OSATOMIC_INTERCEPTORS_BITOP(OSAtomicTestAndSet, __tsan_atomic8_fetch_or,
                             0x80u >> bit_index)