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Avoid triggering assert when program calls OSAtomicCompareAndSwapLong 

A previous change brought the new, relaxed implementation of "on failure
memory ordering" for synchronization primitives in LLVM over to TSan
land [1].  It included the following assert:
```
// 31.7.2.18: "The failure argument shall not be memory_order_release
// nor memory_order_acq_rel". LLVM (2021-05) fallbacks to Monotonic
// (mo_relaxed) when those are used.
CHECK(IsLoadOrder(fmo));

static bool IsLoadOrder(morder mo) {
  return mo == mo_relaxed || mo == mo_consume
      || mo == mo_acquire || mo == mo_seq_cst;
}
```

A previous workaround for a false positive when using an old Darwin
synchronization API assumed this failure mode to be unused and passed a
dummy value [2].  We update this value to `mo_relaxed` which is also the
value used by the actual implementation to avoid triggering the assert.

[1] https://reviews.llvm.org/D99434
[2] https://reviews.llvm.org/D21733

rdar://78122243

Differential Revision: https://reviews.llvm.org/D105844
This commit is contained in:
Julian Lettner 2021-07-12 14:00:45 -07:00
parent 68ae8bacfc
commit 1893b630fe
1 changed files with 5 additions and 4 deletions
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9
compiler-rt/lib/tsan/rtl/tsan_interceptors_mac.cpp
View File

@ -44,8 +44,9 @@ namespace __tsan {
// 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;
static constexpr morder kMacOrderBarrier = mo_acq_rel;
static constexpr morder kMacOrderNonBarrier = mo_acq_rel;
static constexpr morder kMacFailureOrder = mo_relaxed;
#define OSATOMIC_INTERCEPTOR(return_t, t, tsan_t, f, tsan_atomic_f, mo) \
TSAN_INTERCEPTOR(return_t, f, t x, volatile t *ptr) { \
@ -110,7 +111,7 @@ OSATOMIC_INTERCEPTORS_BITWISE(OSAtomicXor, fetch_xor,
SCOPED_TSAN_INTERCEPTOR(f, old_value, new_value, ptr); \
return tsan_atomic_f##_compare_exchange_strong( \
(volatile tsan_t *)ptr, (tsan_t *)&old_value, (tsan_t)new_value, \
kMacOrderNonBarrier, kMacOrderNonBarrier); \
kMacOrderNonBarrier, kMacFailureOrder); \
} \
\
TSAN_INTERCEPTOR(bool, f##Barrier, t old_value, t new_value, \
@ -118,7 +119,7 @@ OSATOMIC_INTERCEPTORS_BITWISE(OSAtomicXor, fetch_xor,
SCOPED_TSAN_INTERCEPTOR(f##Barrier, old_value, new_value, ptr); \
return tsan_atomic_f##_compare_exchange_strong( \
(volatile tsan_t *)ptr, (tsan_t *)&old_value, (tsan_t)new_value, \
kMacOrderBarrier, kMacOrderNonBarrier); \
kMacOrderBarrier, kMacFailureOrder); \
}
OSATOMIC_INTERCEPTORS_CAS(OSAtomicCompareAndSwapInt, __tsan_atomic32, a32, int)