text: // INFO: task can't die in msleep
  // https://syzkaller.appspot.com/bug?id=3a9c5d436cf1afce2cd6
  // status:0
  // autogenerated by syzkaller (https://github.com/google/syzkaller)
  
  #define _GNU_SOURCE
  
  #include <dirent.h>
  #include <endian.h>
  #include <errno.h>
  #include <fcntl.h>
  #include <pthread.h>
  #include <signal.h>
  #include <stdarg.h>
  #include <stdbool.h>
  #include <stdint.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  #include <sys/ioctl.h>
  #include <sys/mount.h>
  #include <sys/prctl.h>
  #include <sys/stat.h>
  #include <sys/syscall.h>
  #include <sys/types.h>
  #include <sys/wait.h>
  #include <time.h>
  #include <unistd.h>
  
  #include <linux/futex.h>
  
  static unsigned long long procid;
  
  static void sleep_ms(uint64_t ms)
  {
    usleep(ms * 1000);
  }
  
  static uint64_t current_time_ms(void)
  {
    struct timespec ts;
    if (clock_gettime(CLOCK_MONOTONIC, &ts))
      exit(1);
    return (uint64_t)ts.tv_sec * 1000 + (uint64_t)ts.tv_nsec / 1000000;
  }
  
  static void use_temporary_dir(void)
  {
    char tmpdir_template[] = "./syzkaller.XXXXXX";
    char* tmpdir = mkdtemp(tmpdir_template);
    if (!tmpdir)
      exit(1);
    if (chmod(tmpdir, 0777))
      exit(1);
    if (chdir(tmpdir))
      exit(1);
  }
  
  static void thread_start(void* (*fn)(void*), void* arg)
  {
    pthread_t th;
    pthread_attr_t attr;
    pthread_attr_init(&attr);
    pthread_attr_setstacksize(&attr, 128 << 10);
    int i = 0;
    for (; i < 100; i++) {
      if (pthread_create(&th, &attr, fn, arg) == 0) {
        pthread_attr_destroy(&attr);
        return;
      }
      if (errno == EAGAIN) {
        usleep(50);
        continue;
      }
      break;
    }
    exit(1);
  }
  
  typedef struct {
    int state;
  } event_t;
  
  static void event_init(event_t* ev)
  {
    ev->state = 0;
  }
  
  static void event_reset(event_t* ev)
  {
    ev->state = 0;
  }
  
  static void event_set(event_t* ev)
  {
    if (ev->state)
      exit(1);
    __atomic_store_n(&ev->state, 1, __ATOMIC_RELEASE);
    syscall(SYS_futex, &ev->state, FUTEX_WAKE | FUTEX_PRIVATE_FLAG, 1000000);
  }
  
  static void event_wait(event_t* ev)
  {
    while (!__atomic_load_n(&ev->state, __ATOMIC_ACQUIRE))
      syscall(SYS_futex, &ev->state, FUTEX_WAIT | FUTEX_PRIVATE_FLAG, 0, 0);
  }
  
  static int event_isset(event_t* ev)
  {
    return __atomic_load_n(&ev->state, __ATOMIC_ACQUIRE);
  }
  
  static int event_timedwait(event_t* ev, uint64_t timeout)
  {
    uint64_t start = current_time_ms();
    uint64_t now = start;
    for (;;) {
      uint64_t remain = timeout - (now - start);
      struct timespec ts;
      ts.tv_sec = remain / 1000;
      ts.tv_nsec = (remain % 1000) * 1000 * 1000;
      syscall(SYS_futex, &ev->state, FUTEX_WAIT | FUTEX_PRIVATE_FLAG, 0, &ts);
      if (__atomic_load_n(&ev->state, __ATOMIC_ACQUIRE))
        return 1;
      now = current_time_ms();
      if (now - start > timeout)
        return 0;
    }
  }
  
  static bool write_file(const char* file, const char* what, ...)
  {
    char buf[1024];
    va_list args;
    va_start(args, what);
    vsnprintf(buf, sizeof(buf), what, args);
    va_end(args);
    buf[sizeof(buf) - 1] = 0;
    int len = strlen(buf);
    int fd = open(file, O_WRONLY | O_CLOEXEC);
    if (fd == -1)
      return false;
    if (write(fd, buf, len) != len) {
      int err = errno;
      close(fd);
      errno = err;
      return false;
    }
    close(fd);
    return true;
  }
  
  #define FS_IOC_SETFLAGS _IOW('f', 2, long)
  static void remove_dir(const char* dir)
  {
    int iter = 0;
    DIR* dp = 0;
  retry:
    while (umount2(dir, MNT_DETACH) == 0) {
    }
    dp = opendir(dir);
    if (dp == NULL) {
      if (errno == EMFILE) {
        exit(1);
      }
      exit(1);
    }
    struct dirent* ep = 0;
    while ((ep = readdir(dp))) {
      if (strcmp(ep->d_name, ".") == 0 || strcmp(ep->d_name, "..") == 0)
        continue;
      char filename[FILENAME_MAX];
      snprintf(filename, sizeof(filename), "%s/%s", dir, ep->d_name);
      while (umount2(filename, MNT_DETACH) == 0) {
      }
      struct stat st;
      if (lstat(filename, &st))
        exit(1);
      if (S_ISDIR(st.st_mode)) {
        remove_dir(filename);
        continue;
      }
      int i;
      for (i = 0;; i++) {
        if (unlink(filename) == 0)
          break;
        if (errno == EPERM) {
          int fd = open(filename, O_RDONLY);
          if (fd != -1) {
            long flags = 0;
            if (ioctl(fd, FS_IOC_SETFLAGS, &flags) == 0) {
            }
            close(fd);
            continue;
          }
        }
        if (errno == EROFS) {
          break;
        }
        if (errno != EBUSY || i > 100)
          exit(1);
        if (umount2(filename, MNT_DETACH))
          exit(1);
      }
    }
    closedir(dp);
    for (int i = 0;; i++) {
      if (rmdir(dir) == 0)
        break;
      if (i < 100) {
        if (errno == EPERM) {
          int fd = open(dir, O_RDONLY);
          if (fd != -1) {
            long flags = 0;
            if (ioctl(fd, FS_IOC_SETFLAGS, &flags) == 0) {
            }
            close(fd);
            continue;
          }
        }
        if (errno == EROFS) {
          break;
        }
        if (errno == EBUSY) {
          if (umount2(dir, MNT_DETACH))
            exit(1);
          continue;
        }
        if (errno == ENOTEMPTY) {
          if (iter < 100) {
            iter++;
            goto retry;
          }
        }
      }
      exit(1);
    }
  }
  
  static void kill_and_wait(int pid, int* status)
  {
    kill(-pid, SIGKILL);
    kill(pid, SIGKILL);
    for (int i = 0; i < 100; i++) {
      if (waitpid(-1, status, WNOHANG | __WALL) == pid)
        return;
      usleep(1000);
    }
    DIR* dir = opendir("/sys/fs/fuse/connections");
    if (dir) {
      for (;;) {
        struct dirent* ent = readdir(dir);
        if (!ent)
          break;
        if (strcmp(ent->d_name, ".") == 0 || strcmp(ent->d_name, "..") == 0)
          continue;
        char abort[300];
        snprintf(abort, sizeof(abort), "/sys/fs/fuse/connections/%s/abort",
                 ent->d_name);
        int fd = open(abort, O_WRONLY);
        if (fd == -1) {
          continue;
        }
        if (write(fd, abort, 1) < 0) {
        }
        close(fd);
      }
      closedir(dir);
    } else {
    }
    while (waitpid(-1, status, __WALL) != pid) {
    }
  }
  
  static void setup_test()
  {
    prctl(PR_SET_PDEATHSIG, SIGKILL, 0, 0, 0);
    setpgrp();
    write_file("/proc/self/oom_score_adj", "1000");
  }
  
  static void setup_sysctl()
  {
    static struct {
      const char* name;
      const char* data;
    } files[] = {
        {"/sys/kernel/debug/x86/nmi_longest_ns", "10000000000"},
        {"/proc/sys/kernel/hung_task_check_interval_secs", "20"},
        {"/proc/sys/net/core/bpf_jit_kallsyms", "1"},
        {"/proc/sys/net/core/bpf_jit_harden", "0"},
        {"/proc/sys/kernel/kptr_restrict", "0"},
        {"/proc/sys/kernel/softlockup_all_cpu_backtrace", "1"},
        {"/proc/sys/fs/mount-max", "100"},
        {"/proc/sys/vm/oom_dump_tasks", "0"},
        {"/proc/sys/debug/exception-trace", "0"},
        {"/proc/sys/kernel/printk", "7 4 1 3"},
        {"/proc/sys/net/ipv4/ping_group_range", "0 65535"},
        {"/proc/sys/kernel/keys/gc_delay", "1"},
        {"/proc/sys/vm/nr_overcommit_hugepages", "4"},
        {"/proc/sys/vm/oom_kill_allocating_task", "1"},
    };
    for (size_t i = 0; i < sizeof(files) / sizeof(files[0]); i++) {
      if (!write_file(files[i].name, files[i].data))
        printf("write to %s failed: %s\n", files[i].name, strerror(errno));
    }
  }
  
  struct thread_t {
    int created, call;
    event_t ready, done;
  };
  
  static struct thread_t threads[16];
  static void execute_call(int call);
  static int running;
  
  static void* thr(void* arg)
  {
    struct thread_t* th = (struct thread_t*)arg;
    for (;;) {
      event_wait(&th->ready);
      event_reset(&th->ready);
      execute_call(th->call);
      __atomic_fetch_sub(&running, 1, __ATOMIC_RELAXED);
      event_set(&th->done);
    }
    return 0;
  }
  
  static void execute_one(void)
  {
    int i, call, thread;
    for (call = 0; call < 3; call++) {
      for (thread = 0; thread < (int)(sizeof(threads) / sizeof(threads[0]));
           thread++) {
        struct thread_t* th = &threads[thread];
        if (!th->created) {
          th->created = 1;
          event_init(&th->ready);
          event_init(&th->done);
          event_set(&th->done);
          thread_start(thr, th);
        }
        if (!event_isset(&th->done))
          continue;
        event_reset(&th->done);
        th->call = call;
        __atomic_fetch_add(&running, 1, __ATOMIC_RELAXED);
        event_set(&th->ready);
        event_timedwait(&th->done, 50);
        break;
      }
    }
    for (i = 0; i < 100 && __atomic_load_n(&running, __ATOMIC_RELAXED); i++)
      sleep_ms(1);
  }
  
  static void execute_one(void);
  
  #define WAIT_FLAGS __WALL
  
  static void loop(void)
  {
    int iter = 0;
    for (;; iter++) {
      char cwdbuf[32];
      sprintf(cwdbuf, "./%d", iter);
      if (mkdir(cwdbuf, 0777))
        exit(1);
      int pid = fork();
      if (pid < 0)
        exit(1);
      if (pid == 0) {
        if (chdir(cwdbuf))
          exit(1);
        setup_test();
        execute_one();
        exit(0);
      }
      int status = 0;
      uint64_t start = current_time_ms();
      for (;;) {
        if (waitpid(-1, &status, WNOHANG | WAIT_FLAGS) == pid)
          break;
        sleep_ms(1);
        if (current_time_ms() - start < 5000) {
          continue;
        }
        kill_and_wait(pid, &status);
        break;
      }
      remove_dir(cwdbuf);
    }
  }
  
  uint64_t r[1] = {0x0};
  
  void execute_call(int call)
  {
    intptr_t res = 0;
    switch (call) {
    case 0:
      syscall(__NR_clone, 0x40000200ul, 0ul, 0ul, 0ul, 0ul);
      break;
    case 1:
      res = syscall(__NR_gettid);
      if (res != -1)
        r[0] = res;
      break;
    case 2:
      syscall(__NR_tkill, r[0], 0x39);
      break;
    }
  }
  int main(void)
  {
    syscall(__NR_mmap, 0x1ffff000ul, 0x1000ul, 0ul, 0x32ul, -1, 0ul);
    syscall(__NR_mmap, 0x20000000ul, 0x1000000ul, 7ul, 0x32ul, -1, 0ul);
    syscall(__NR_mmap, 0x21000000ul, 0x1000ul, 0ul, 0x32ul, -1, 0ul);
    setup_sysctl();
    for (procid = 0; procid < 6; procid++) {
      if (fork() == 0) {
        use_temporary_dir();
        loop();
      }
    }
    sleep(1000000);
    return 0;
  }
  