71 lines
2.6 KiB
C++
71 lines
2.6 KiB
C++
//===-- tsan_libdispatch_mac.cc -------------------------------------------===//
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file is a part of ThreadSanitizer (TSan), a race detector.
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//
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// Mac-specific libdispatch (GCD) support.
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//===----------------------------------------------------------------------===//
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#include "sanitizer_common/sanitizer_platform.h"
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#if SANITIZER_MAC
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#include "sanitizer_common/sanitizer_common.h"
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#include "interception/interception.h"
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#include "tsan_interceptors.h"
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#include "tsan_platform.h"
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#include "tsan_rtl.h"
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#include <dispatch/dispatch.h>
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#include <pthread.h>
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namespace __tsan {
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// GCD's dispatch_once implementation has a fast path that contains a racy read
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// and it's inlined into user's code. Furthermore, this fast path doesn't
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// establish a proper happens-before relations between the initialization and
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// code following the call to dispatch_once. We could deal with this in
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// instrumented code, but there's not much we can do about it in system
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// libraries. Let's disable the fast path (by never storing the value ~0 to
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// predicate), so the interceptor is always called, and let's add proper release
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// and acquire semantics. Since TSan does not see its own atomic stores, the
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// race on predicate won't be reported - the only accesses to it that TSan sees
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// are the loads on the fast path. Loads don't race. Secondly, dispatch_once is
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// both a macro and a real function, we want to intercept the function, so we
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// need to undefine the macro.
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#undef dispatch_once
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TSAN_INTERCEPTOR(void, dispatch_once, dispatch_once_t *predicate,
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dispatch_block_t block) {
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SCOPED_TSAN_INTERCEPTOR(dispatch_once, predicate, block);
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atomic_uint32_t *a = reinterpret_cast<atomic_uint32_t *>(predicate);
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u32 v = atomic_load(a, memory_order_acquire);
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if (v == 0 &&
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atomic_compare_exchange_strong(a, &v, 1, memory_order_relaxed)) {
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block();
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Release(thr, pc, (uptr)a);
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atomic_store(a, 2, memory_order_release);
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} else {
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while (v != 2) {
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internal_sched_yield();
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v = atomic_load(a, memory_order_acquire);
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}
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Acquire(thr, pc, (uptr)a);
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}
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}
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#undef dispatch_once_f
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TSAN_INTERCEPTOR(void, dispatch_once_f, dispatch_once_t *predicate,
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void *context, dispatch_function_t function) {
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SCOPED_TSAN_INTERCEPTOR(dispatch_once_f, predicate, context, function);
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WRAP(dispatch_once)(predicate, ^(void) {
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function(context);
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});
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}
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} // namespace __tsan
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#endif // SANITIZER_MAC
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