compiler-rt/test/tsan/stack_sync_reuse.cpp

   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