fusl/src/aio/aio_suspend.c

#include <aio.h>
#include <errno.h>
#include <time.h>
#include "atomic.h"
#include "libc.h"
#include "pthread_impl.h"

extern volatile int __aio_fut;

int aio_suspend(const struct aiocb* const cbs[],
                int cnt,
                const struct timespec* ts) {
  int i, tid = 0, ret, expect = 0;
  struct timespec at;
  volatile int dummy_fut, *pfut;
  int nzcnt = 0;
  const struct aiocb* cb = 0;

  pthread_testcancel();

  if (cnt < 0) {
    errno = EINVAL;
    return -1;
  }

  for (i = 0; i < cnt; i++)
    if (cbs[i]) {
      if (aio_error(cbs[i]) != EINPROGRESS)
        return 0;
      nzcnt++;
      cb = cbs[i];
    }

  if (ts) {
    clock_gettime(CLOCK_MONOTONIC, &at);
    at.tv_sec += ts->tv_sec;
    if ((at.tv_nsec += ts->tv_nsec) >= 1000000000) {
      at.tv_nsec -= 1000000000;
      at.tv_sec++;
    }
  }

  for (;;) {
    for (i = 0; i < cnt; i++)
      if (cbs[i] && aio_error(cbs[i]) != EINPROGRESS)
        return 0;

    switch (nzcnt) {
      case 0:
        pfut = &dummy_fut;
        break;
      case 1:
        pfut = (void*)&cb->__err;
        expect = EINPROGRESS | 0x80000000;
        a_cas(pfut, EINPROGRESS, expect);
        break;
      default:
        pfut = &__aio_fut;
        if (!tid)
          tid = __pthread_self()->tid;
        expect = a_cas(pfut, 0, tid);
        if (!expect)
          expect = tid;
        /* Need to recheck the predicate before waiting. */
        for (i = 0; i < cnt; i++)
          if (cbs[i] && aio_error(cbs[i]) != EINPROGRESS)
            return 0;
        break;
    }

    ret = __timedwait_cp(pfut, expect, CLOCK_MONOTONIC, ts ? &at : 0, 1);

    switch (ret) {
      case ETIMEDOUT:
        ret = EAGAIN;
      case ECANCELED:
      case EINTR:
        errno = ret;
        return -1;
    }
  }
}