eventfd.c

#include <stdio.h>
#include <stdlib.h>
#include <sys/eventfd.h>
#include <unistd.h>

typedef struct state {
  int tx, rx;  // relative to parent
} state;

state *new_state() { return calloc(sizeof(state), 1); }

void free_state(state *state) { free(state); }

int pre_fork_setup(state *state) {
  if ((state->tx = eventfd(0 /* initval */, 0 /* flags */)) == -1) {
    // uh-oh
  }
  if ((state->rx = eventfd(0 /* initval */, 0 /* flags */)) == -1) {
    // uh-oh
  }
  return 0;
}

int cleanup(state *state __attribute__((unused))) { return 0; }

int child_post_fork_setup(state *state __attribute__((unused))) { return 0; }

int child_warmup(int warmup_iters __attribute__((unused)),
                 state *state __attribute__((unused))) {
  return 0;
}

int child_loop(int warmup_iters __attribute__((unused)), state *state) {
  for (;;) {
    char msg[8];
    read(state->tx, msg, 8);
    write(state->rx, "\0\0\0\0\0\0\0\1", 8);
  }
  return 0;
}

int child_cleanup(state *state __attribute__((unused))) { return 0; }

int parent_post_fork_setup(state *state __attribute__((unused))) { return 0; }

int parent_warmup(int warmup_iters, state *state) {
  int i;

  for (i = 0; i < warmup_iters; ++i) {
    char resp[8];
    if (write(state->tx, "\0\0\0\0\0\0\0\1", 8) == -1) {
      perror("could not write");
      break;
    };

    if (read(state->rx, &resp, 8) == -1) {
      perror("could not read");
      break;
    }
  }
  return 0;
}

int parent_loop(int iters, state *state) {
  int i;

  for (i = 0; i < iters; ++i) {
    char resp[8];
    if (write(state->tx, "\0\0\0\0\0\0\0\1", 8) == -1) {
      perror("could not write");
      break;
    };

    if (read(state->rx, &resp, 8) == -1) {
      perror("could not read");
      break;
    }
  }
  return 0;
}

int parent_cleanup(state *state __attribute__((unused))) { return 0; }