mingw-w64-libraries/winpthreads/tests/pthread_mutex/normal-static-lock-recursive.c

/*
   Copyright (c) 2026 mingw-w64 project

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*/

#include "test.h"

/**
 * Test Summary:
 *
 * Main thread M creates (statically initialized) mutex L with type
 * `PTHREAD_MUTEX_NORMAL`.
 *
 * Thread A locks L.
 *
 * Thread A attempts to lock L again; this must result in a dead lock.
 *
 * Thread M unlocks and destroys L.
 */

static LONG IsThreadABlocked = FALSE;

static void *ThreadA(void *arg)
{
  pthread_mutex_t *mutex = arg;

  assert(pthread_mutex_lock(mutex) == 0);
  /**
   * Signal thread M that thread A locked L.
   */
  InterlockedExchange(&IsThreadABlocked, TRUE);
  /**
   * Attempt to recursively lock NORMAL mutex must result in a dead lock.
   * Wait for main thread to unlock...
   */
  assert(pthread_mutex_lock(mutex) == 0);
  /**
   * Signal thread M that thread A was unblocked.
   */
  InterlockedExchange(&IsThreadABlocked, FALSE);
  assert(pthread_mutex_unlock(mutex) == 0);

  return arg;
}

int main(void)
{
  pthread_mutex_t mutex = PTHREAD_NORMAL_MUTEX_INITIALIZER;
  pthread_t thread;
  void *result;

  assert(pthread_create(&thread, NULL, ThreadA, &mutex) == 0);
  /**
   * Wait until thread A locks L.
   */
  while (!IsThreadABlocked) {
    YieldProcessor();
  }
  Sleep(10);
  /**
   * Thread A must be deadlocked.
   */
  assert(IsThreadABlocked);
  /**
   * POSIX states that calling `pthread_mutex_unlock` on NORMAL mutex that is
   * not owned by the calling thread is undefined behavior.
   *
   * Our implementation for NORMAL mutexes does not check ownership at all,
   * so call to `pthread_mutex_unlock` on a valid NORMAL mutex always succeeds.
   */
  do {
    assert(pthread_mutex_unlock(&mutex) == 0);
    YieldProcessor();
  } while (IsThreadABlocked);
  assert(pthread_join (thread, &result) == 0);
  assert(result == &mutex);
  assert(pthread_mutex_destroy(&mutex) == 0);

  return 0;
}