llvm-project/compiler-rt/test/tsan/signal_recursive.cpp

// RUN: %clang_tsan -O1 %s -o %t && %run %t 2>&1 | FileCheck %s

// Test case for recursive signal handlers, adopted from:
// https://github.com/google/sanitizers/issues/478

// UNSUPPORTED: darwin

#include "test.h"
#include <semaphore.h>
#include <signal.h>
#include <errno.h>

static const int kSigSuspend = SIGUSR1;
static const int kSigRestart = SIGUSR2;

static sem_t g_thread_suspend_ack_sem;

static volatile bool g_busy_thread_garbage_collected;

static void SaveRegistersInStack() {
  // Mono walks thread stacks to detect unreferenced objects.
  // If last object reference is kept in register the object will be collected
  // This is why threads can't be suspended with something like pthread_suspend
}

static void fail(const char *what) {
  fprintf(stderr, "FAILED: %s (errno=%d)\n", what, errno);
  exit(1);
}

static void CheckSigBlocked(const sigset_t &oldset, const sigset_t &newset,
                            int sig) {
  const int is_old_member = sigismember(&oldset, sig);
  const int is_new_member = sigismember(&newset, sig);

  if (is_old_member == -1 || is_new_member == -1)
    fail("sigismember failed");

  if (is_old_member != is_new_member)
    fail("restoring signals failed");
}

sigset_t GetCurrentSigSet() {
  sigset_t set;
  if (sigemptyset(&set) != 0)
    fail("sigemptyset failed");

  if (pthread_sigmask(SIG_BLOCK, NULL, &set) != 0)
    fail("pthread_sigmask failed");

  return set;
}

static void SuspendHandler(int sig) {
  int old_errno = errno;
  SaveRegistersInStack();

  // Enable kSigRestart handling, tsan disables signals around signal handlers.
  const auto oldset = GetCurrentSigSet();

  // Acknowledge that thread is saved and suspended
  if (sem_post(&g_thread_suspend_ack_sem) != 0)
    fail("sem_post failed");

  // Wait for wakeup signal.
  sigset_t sigset;
  sigemptyset(&sigset);
  if (sigsuspend(&sigset) != 0 && errno != EINTR)
    fail("sigsuspend failed");

  const auto newset = GetCurrentSigSet();

  // Check that the same signals are blocked as before
  CheckSigBlocked(oldset, newset, kSigSuspend);
  CheckSigBlocked(oldset, newset, kSigRestart);

  // Acknowledge that thread restarted
  if (sem_post(&g_thread_suspend_ack_sem) != 0)
    fail("sem_post failed");

  g_busy_thread_garbage_collected = true;

  errno = old_errno;
}

static void RestartHandler(int sig) {}

static void WaitSem() {
  while (sem_wait(&g_thread_suspend_ack_sem) != 0) {
    if (errno != EINTR)
      fail("sem_wait failed");
  }
}

static void StopWorld(pthread_t thread) {
  if (pthread_kill(thread, kSigSuspend) != 0)
    fail("pthread_kill failed");

  WaitSem();
}

static void StartWorld(pthread_t thread) {
  if (pthread_kill(thread, kSigRestart) != 0)
    fail("pthread_kill failed");

  WaitSem();
}

static void CollectGarbage(pthread_t thread) {
  // Wait for the thread to start
  WaitSem();

  StopWorld(thread);
  // Walk stacks
  StartWorld(thread);
}

static void Init() {
  if (sem_init(&g_thread_suspend_ack_sem, 0, 0) != 0)
    fail("sem_init failed");

  struct sigaction act = {};
  act.sa_flags = SA_RESTART;
  act.sa_handler = &SuspendHandler;
  if (sigaction(kSigSuspend, &act, NULL) != 0)
    fail("sigaction failed");
  act.sa_handler = &RestartHandler;
  if (sigaction(kSigRestart, &act, NULL) != 0)
    fail("sigaction failed");
}

void* BusyThread(void *arg) {
  (void)arg;
  const auto oldset = GetCurrentSigSet();

  if (sem_post(&g_thread_suspend_ack_sem) != 0)
    fail("sem_post failed");

  while (!g_busy_thread_garbage_collected) {
    usleep(100); // Tsan deadlocks without these sleeps
  }

  const auto newset = GetCurrentSigSet();

  // Check that we have the same signals blocked as before
  CheckSigBlocked(oldset, newset, kSigSuspend);
  CheckSigBlocked(oldset, newset, kSigRestart);

  return NULL;
}

int main(int argc, const char *argv[]) {
  Init();

  pthread_t busy_thread;
  if (pthread_create(&busy_thread, NULL, &BusyThread, NULL) != 0)
    fail("pthread_create failed");

  CollectGarbage(busy_thread);
  if (pthread_join(busy_thread, 0) != 0)
    fail("pthread_join failed");

  fprintf(stderr, "DONE\n");

  return 0;
}

// CHECK-NOT: FAILED
// CHECK-NOT: ThreadSanitizer CHECK failed
// CHECK-NOT: WARNING: ThreadSanitizer:
// CHECK: DONE