1 // RUN: %clang_tsan -O1 %s -o %t && %run %t 2>&1 | FileCheck %s 2 #include "test.h" 3 4 // Test case https://github.com/google/sanitizers/issues/494 5 // Tsan sees false HB edge on address pointed to by syncp variable. 6 // It is false because when acquire is done syncp points to a var in one frame, 7 // and during release it points to a var in a different frame. 8 // The code is somewhat tricky because it prevents compiler from optimizing 9 // our accesses away, structured to not introduce other data races and 10 // not introduce other synchronization, and to arrange the vars in different 11 // frames to occupy the same address. 12 13 // The data race CHECK-NOT below actually must be CHECK, because the program 14 // does contain the data race on global. 15 16 // CHECK-NOT: WARNING: ThreadSanitizer: data race 17 // CHECK: DONE 18 19 long global; 20 long *syncp; 21 long *addr; 22 long sink; 23 24 void *Thread(void *x) { 25 while (__atomic_load_n(&syncp, __ATOMIC_ACQUIRE) == 0) 26 usleep(1000); // spin wait 27 global = 42; 28 __atomic_store_n(syncp, 1, __ATOMIC_RELEASE); 29 __atomic_store_n(&syncp, 0, __ATOMIC_RELAXED); 30 return NULL; 31 } 32 33 void __attribute__((noinline)) foobar() { 34 __attribute__((aligned(64))) long s; 35 36 addr = &s; 37 __atomic_store_n(&s, 0, __ATOMIC_RELAXED); 38 __atomic_store_n(&syncp, &s, __ATOMIC_RELEASE); 39 while (__atomic_load_n(&syncp, __ATOMIC_RELAXED) != 0) 40 usleep(1000); // spin wait 41 } 42 43 void __attribute__((noinline)) barfoo() { 44 __attribute__((aligned(64))) long s; 45 46 if (addr != &s) { 47 printf("address mismatch addr=%p &s=%p\n", addr, &s); 48 exit(1); 49 } 50 __atomic_store_n(&addr, &s, __ATOMIC_RELAXED); 51 __atomic_store_n(&s, 0, __ATOMIC_RELAXED); 52 sink = __atomic_load_n(&s, __ATOMIC_ACQUIRE); 53 global = 43; 54 } 55 56 int main() { 57 pthread_t t; 58 pthread_create(&t, 0, Thread, 0); 59 foobar(); 60 barfoo(); 61 pthread_join(t, 0); 62 if (sink != 0) 63 exit(1); 64 fprintf(stderr, "DONE\n"); 65 return 0; 66 } 67 68
