68 lines · cpp
1// RUN: %clang_tsan -O1 %s -o %t && %run %t 2>&1 | FileCheck %s2#include "test.h"3 4// Test case https://github.com/google/sanitizers/issues/4945// 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 optimizing9// our accesses away, structured to not introduce other data races and10// not introduce other synchronization, and to arrange the vars in different11// frames to occupy the same address.12 13// The data race CHECK-NOT below actually must be CHECK, because the program14// does contain the data race on global.15 16// CHECK-NOT: WARNING: ThreadSanitizer: data race17// CHECK: DONE18 19long global;20long *syncp;21long *addr;22long sink;23 24void *Thread(void *x) {25 while (__atomic_load_n(&syncp, __ATOMIC_ACQUIRE) == 0)26 usleep(1000); // spin wait27 global = 42;28 __atomic_store_n(syncp, 1, __ATOMIC_RELEASE);29 __atomic_store_n(&syncp, 0, __ATOMIC_RELAXED);30 return NULL;31}32 33void __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 wait41}42 43void __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 56int 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