src/core/iomgr/iomgr.c

/*
 *
 * Copyright 2015, Google Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
 *     * Neither the name of Google Inc. nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

#include "src/core/iomgr/iomgr.h"

#include <assert.h>
#include <stdlib.h>

#include "src/core/iomgr/iomgr_internal.h"
#include "src/core/iomgr/alarm_internal.h"
#include <grpc/support/alloc.h>
#include <grpc/support/log.h>
#include <grpc/support/thd.h>
#include <grpc/support/sync.h>

static gpr_mu g_mu;
static gpr_cv g_rcv;
static grpc_iomgr_closure *g_cbs_head = NULL;
static grpc_iomgr_closure *g_cbs_tail = NULL;
static int g_shutdown;
static int g_refs;
static gpr_event g_background_callback_executor_done;

/* Execute followup callbacks continuously.
   Other threads may check in and help during pollset_work() */
static void background_callback_executor(void *ignored) {
  gpr_mu_lock(&g_mu);
  while (!g_shutdown) {
    gpr_timespec deadline = gpr_inf_future;
    gpr_timespec short_deadline =
        gpr_time_add(gpr_now(), gpr_time_from_millis(100));
    if (g_cbs_head) {
      grpc_iomgr_closure *iocb = g_cbs_head;
      int is_cb_ext_managed;
      g_cbs_head = iocb->next;
      if (!g_cbs_head) g_cbs_tail = NULL;
      gpr_mu_unlock(&g_mu);
      /* capture the managed state, as the callback may deallocate itself */
      is_cb_ext_managed = iocb->is_ext_managed;
      assert(iocb->success >= 0);
      iocb->cb(iocb->cb_arg, iocb->success);
      if (!is_cb_ext_managed) {
        gpr_free(iocb);
      }
      gpr_mu_lock(&g_mu);
    } else if (grpc_alarm_check(&g_mu, gpr_now(), &deadline)) {
    } else {
      gpr_mu_unlock(&g_mu);
      gpr_sleep_until(gpr_time_min(short_deadline, deadline));
      gpr_mu_lock(&g_mu);
    }
  }
  gpr_mu_unlock(&g_mu);
  gpr_event_set(&g_background_callback_executor_done, (void *)1);
}

void grpc_kick_poller(void) {
  /* Empty. The background callback executor polls periodically. The activity
   * the kicker is trying to draw the executor's attention to will be picked up
   * either by one of the periodic wakeups or by one of the polling application
   * threads. */
}

void grpc_iomgr_init(void) {
  gpr_thd_id id;
  gpr_mu_init(&g_mu);
  gpr_cv_init(&g_rcv);
  grpc_alarm_list_init(gpr_now());
  g_refs = 0;
  grpc_iomgr_platform_init();
  gpr_event_init(&g_background_callback_executor_done);
  gpr_thd_new(&id, background_callback_executor, NULL, NULL);
}

void grpc_iomgr_shutdown(void) {
  grpc_iomgr_closure *iocb;
  gpr_timespec shutdown_deadline =
      gpr_time_add(gpr_now(), gpr_time_from_seconds(10));


  gpr_mu_lock(&g_mu);
  g_shutdown = 1;
  while (g_cbs_head || g_refs) {
    gpr_log(GPR_DEBUG, "Waiting for %d iomgr objects to be destroyed%s", g_refs,
            g_cbs_head ? " and executing final callbacks" : "");
    while (g_cbs_head) {
      int is_cb_ext_managed;
      iocb = g_cbs_head;
      g_cbs_head = iocb->next;
      if (!g_cbs_head) g_cbs_tail = NULL;
      gpr_mu_unlock(&g_mu);

      /* capture the managed state, as the callback may deallocate itself */
      is_cb_ext_managed = iocb->is_ext_managed;
      iocb->cb(iocb->cb_arg, 0);
      if (!is_cb_ext_managed) {
        gpr_free(iocb);
      }
      gpr_mu_lock(&g_mu);
    }
    if (g_refs) {
      int timeout = 0;
      gpr_timespec short_deadline = gpr_time_add(gpr_now(),
                                                 gpr_time_from_millis(100));
      while (gpr_cv_wait(&g_rcv, &g_mu, short_deadline) && g_cbs_head == NULL) {
        if (gpr_time_cmp(gpr_now(), shutdown_deadline) > 0) {
          timeout = 1;
          break;
        }
      }
      if (timeout) {
        gpr_log(GPR_DEBUG,
                "Failed to free %d iomgr objects before shutdown deadline: "
                "memory leaks are likely",
                g_refs);
        break;
      }
    }
  }
  gpr_mu_unlock(&g_mu);

  grpc_kick_poller();
  gpr_event_wait(&g_background_callback_executor_done, gpr_inf_future);

  grpc_iomgr_platform_shutdown();
  grpc_alarm_list_shutdown();
  gpr_mu_destroy(&g_mu);
  gpr_cv_destroy(&g_rcv);
}

void grpc_iomgr_ref(void) {
  gpr_mu_lock(&g_mu);
  ++g_refs;
  gpr_mu_unlock(&g_mu);
}

void grpc_iomgr_unref(void) {
  gpr_mu_lock(&g_mu);
  if (0 == --g_refs) {
    gpr_cv_signal(&g_rcv);
  }
  gpr_mu_unlock(&g_mu);
}

grpc_iomgr_closure *grpc_iomgr_cb_create(grpc_iomgr_cb_func cb, void *cb_arg,
                                    int is_ext_managed) {
  grpc_iomgr_closure *iocb = gpr_malloc(sizeof(grpc_iomgr_closure));
  iocb->cb = cb;
  iocb->cb_arg = cb_arg;
  iocb->is_ext_managed = is_ext_managed;
  iocb->success = -1;  /* uninitialized */
  iocb->next = NULL;
  return iocb;
}

void grpc_iomgr_add_delayed_callback(grpc_iomgr_closure *iocb, int success) {
  iocb->success = success;
  gpr_mu_lock(&g_mu);
  iocb->next = NULL;
  if (!g_cbs_tail) {
    g_cbs_head = g_cbs_tail = iocb;
  } else {
    g_cbs_tail->next = iocb;
    g_cbs_tail = iocb;
  }
  gpr_mu_unlock(&g_mu);
}


void grpc_iomgr_add_callback(grpc_iomgr_closure *iocb) {
  grpc_iomgr_add_delayed_callback(iocb, 1);
}


int grpc_maybe_call_delayed_callbacks(gpr_mu *drop_mu, int success) {
  int n = 0;
  gpr_mu *retake_mu = NULL;
  grpc_iomgr_closure *iocb;
  for (;;) {
    int is_cb_ext_managed;
    /* check for new work */
    if (!gpr_mu_trylock(&g_mu)) {
      break;
    }
    iocb = g_cbs_head;
    if (!iocb) {
      gpr_mu_unlock(&g_mu);
      break;
    }
    g_cbs_head = iocb->next;
    if (!g_cbs_head) g_cbs_tail = NULL;
    gpr_mu_unlock(&g_mu);
    /* if we have a mutex to drop, do so before executing work */
    if (drop_mu) {
      gpr_mu_unlock(drop_mu);
      retake_mu = drop_mu;
      drop_mu = NULL;
    }
    /* capture the managed state, as the callback may deallocate itself */
    is_cb_ext_managed = iocb->is_ext_managed;
    assert(iocb->success >= 0);
    iocb->cb(iocb->cb_arg, success && iocb->success);
    if (!is_cb_ext_managed) {
      gpr_free(iocb);
    }
    n++;
  }
  if (retake_mu) {
    gpr_mu_lock(retake_mu);
  }
  return n;
}