diff --git a/compiler-rt/lib/tsan/rtl/tsan_fd.cpp b/compiler-rt/lib/tsan/rtl/tsan_fd.cpp --- a/compiler-rt/lib/tsan/rtl/tsan_fd.cpp +++ b/compiler-rt/lib/tsan/rtl/tsan_fd.cpp @@ -113,12 +113,17 @@ } d->creation_tid = thr->tid; d->creation_stack = CurrentStackId(thr, pc); + // This prevents false positives on fd_close_norace3.cpp test. + // The mechanics of the false positive are not completely clear, + // but it happens only if global reset is enabled (flush_memory_ms=1) + // and may be related to lost writes during asynchronous MADV_DONTNEED. + SlotLocker locker(thr); if (write) { // To catch races between fd usage and open. MemoryRangeImitateWrite(thr, pc, (uptr)d, 8); } else { // See the dup-related comment in FdClose. - MemoryAccess(thr, pc, (uptr)d, 8, kAccessRead); + MemoryAccess(thr, pc, (uptr)d, 8, kAccessRead | kAccessSlotLocked); } } diff --git a/compiler-rt/test/tsan/fd_close_norace3.cpp b/compiler-rt/test/tsan/fd_close_norace3.cpp new file mode 100644 --- /dev/null +++ b/compiler-rt/test/tsan/fd_close_norace3.cpp @@ -0,0 +1,28 @@ +// RUN: %clangxx_tsan -O1 %s -o %t && %env_tsan_opts=flush_memory_ms=1 %run %t 2>&1 | FileCheck %s +#include "test.h" +#include +#include +#include +#include + +void *Thread(void *stop) { + while (!__atomic_load_n((int *)stop, __ATOMIC_RELAXED)) + close(open("/dev/null", O_RDONLY)); + return 0; +} + +int main() { + int stop = 0; + const int kThreads = 10; + pthread_t th[kThreads]; + for (int i = 0; i < kThreads; i++) + pthread_create(&th[i], 0, Thread, &stop); + sleep(5); + __atomic_store_n(&stop, 1, __ATOMIC_RELAXED); + for (int i = 0; i < kThreads; i++) + pthread_join(th[i], 0); + fprintf(stderr, "DONE\n"); +} + +// CHECK-NOT: WARNING: ThreadSanitizer: data race +// CHECK: DONE