FD is blocked in fifo

[mhomidi]

I was running gvisor testcase on quark and I faced an issue with fifo. The testcase is this:

TEST(FifoTest, Fifo) {
  const std::string fifo = NewTempAbsPath();
  ASSERT_THAT(mknod(fifo.c_str(), S_IFIFO | S_IRUSR | S_IWUSR, 0),
              SyscallSucceeds());

  struct stat st;
  ASSERT_THAT(stat(fifo.c_str(), &st), SyscallSucceeds());
  EXPECT_TRUE(S_ISFIFO(st.st_mode));

  std::string msg = "some std::string";
  std::vector<char> buf(512);

  // Read-end of the pipe.
  ScopedThread t([&fifo, &buf, &msg]() {
    FileDescriptor fd =
        ASSERT_NO_ERRNO_AND_VALUE(OpenRetryEINTR(fifo.c_str(), O_RDONLY));
    EXPECT_THAT(ReadFd(fd.get(), buf.data(), buf.size()),
                SyscallSucceedsWithValue(msg.length()));
    EXPECT_EQ(msg, std::string(buf.data()));
  });
}

The problem is tnat when the write does its job, it closes the file. Then reader comes and open it with same fd but it is blocked when it is reading. Actually it reads first 16 byte, but in the second iteration in ApplyFileIoSyscall, instead of getting zero, it is blocked when it call read syscall.

code of ReadFd and writeFd link to code:

inline ssize_t ReadFd(int fd, void* buf, size_t count) {
  return internal::ApplyFileIoSyscall(
      [&](size_t completed) {
        return read(fd, static_cast<char*>(buf) + completed, count - completed);
      },
      count);
}

inline ssize_t WriteFd(int fd, void const* buf, size_t count) {
  return internal::ApplyFileIoSyscall(
      [&](size_t completed) {
        return write(fd, static_cast<char const*>(buf) + completed,
                     count - completed);
      },
      count);
}

code of ApplyFileIoSyscall link :

ssize_t ApplyFileIoSyscall(F const& f, size_t const count) {
  size_t completed = 0;
  // `do ... while` because some callers actually want to make a syscall with a
  // count of 0.
  do {
    auto const cur = RetryEINTR(f)(completed);
    if (cur < 0) {
      return cur;
    } else if (cur == 0) {
      break;
    }
    completed += cur;
  } while (completed < count);
  return completed;
}