src/core/iomgr/pollset_windows.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 <grpc/support/port_platform.h>

#ifdef GPR_WINSOCK_SOCKET

#include <grpc/support/thd.h>

#include "src/core/iomgr/alarm_internal.h"
#include "src/core/iomgr/iomgr_internal.h"
#include "src/core/iomgr/iocp_windows.h"
#include "src/core/iomgr/pollset.h"
#include "src/core/iomgr/pollset_windows.h"

gpr_mu grpc_polling_mu;
static grpc_pollset_worker *g_active_poller;
static grpc_pollset_worker g_global_root_worker;

void grpc_pollset_global_init() {
  gpr_mu_init(&grpc_polling_mu);
  g_active_poller = NULL;
  g_global_root_worker.links[GRPC_POLLSET_WORKER_LINK_GLOBAL].next =
    g_global_root_worker.links[GRPC_POLLSET_WORKER_LINK_GLOBAL].prev =
    &g_global_root_worker;
}

void grpc_pollset_global_shutdown() {
  gpr_mu_destroy(&grpc_polling_mu);
}

static void remove_worker(grpc_pollset_worker *worker, 
                          grpc_pollset_worker_link_type type) {
  worker->links[type].prev->links[type].next = worker->links[type].next;
  worker->links[type].next->links[type].prev = worker->links[type].prev;
  worker->links[type].next = worker->links[type].prev = worker;
}

static int has_workers(grpc_pollset_worker *root, grpc_pollset_worker_link_type type) {
  return root->links[type].next != root;
}

static grpc_pollset_worker *pop_front_worker(
    grpc_pollset_worker *root, grpc_pollset_worker_link_type type) {
  if (has_workers(root, type)) {
    grpc_pollset_worker *w = root->links[type].next;
    remove_worker(w, type);
    return w;
  } else {
    return NULL;
  }
}

static void push_back_worker(grpc_pollset_worker *root, 
                             grpc_pollset_worker_link_type type, 
                             grpc_pollset_worker *worker) {
  worker->links[type].next = root;
  worker->links[type].prev = worker->links[type].next->links[type].prev;
  worker->links[type].prev->links[type].next = 
    worker->links[type].next->links[type].prev = 
    worker;
}

static void push_front_worker(grpc_pollset_worker *root, 
                              grpc_pollset_worker_link_type type, 
                              grpc_pollset_worker *worker) {
  worker->links[type].prev = root;
  worker->links[type].next = worker->links[type].prev->links[type].next;
  worker->links[type].prev->links[type].next = 
    worker->links[type].next->links[type].prev = 
    worker;
}

/* There isn't really any such thing as a pollset under Windows, due to the
   nature of the IO completion ports. We're still going to provide a minimal
   set of features for the sake of the rest of grpc. But grpc_pollset_work
   won't actually do any polling, and return as quickly as possible. */

void grpc_pollset_init(grpc_pollset *pollset) {
  memset(pollset, 0, sizeof(*pollset));
  pollset->root_worker.links[GRPC_POLLSET_WORKER_LINK_POLLSET].next = 
    pollset->root_worker.links[GRPC_POLLSET_WORKER_LINK_POLLSET].prev = 
    &pollset->root_worker;
}

void grpc_pollset_shutdown(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
                           grpc_closure *closure) {
  gpr_mu_lock(&grpc_polling_mu);
  pollset->shutting_down = 1;
  grpc_pollset_kick(pollset, GRPC_POLLSET_KICK_BROADCAST);
  if (!pollset->is_iocp_worker) {
    grpc_exec_ctx_enqueue(exec_ctx, closure, 1);
  } else {
    pollset->on_shutdown = closure;
  }
  gpr_mu_unlock(&grpc_polling_mu);
}

void grpc_pollset_destroy(grpc_pollset *pollset) {
}

void grpc_pollset_work(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
                       grpc_pollset_worker *worker, gpr_timespec now,
                       gpr_timespec deadline) {
  int added_worker = 0;
  worker->links[GRPC_POLLSET_WORKER_LINK_POLLSET].next = 
    worker->links[GRPC_POLLSET_WORKER_LINK_POLLSET].prev = 
    worker->links[GRPC_POLLSET_WORKER_LINK_GLOBAL].next =
    worker->links[GRPC_POLLSET_WORKER_LINK_GLOBAL].prev =
    NULL;
  worker->kicked = 0;
  worker->pollset = pollset;
  gpr_cv_init(&worker->cv);
  if (grpc_alarm_check(exec_ctx, now, &deadline)) {
    goto done;
  }
  if (!pollset->kicked_without_pollers && !pollset->shutting_down) {
    if (g_active_poller == NULL) {
      grpc_pollset_worker *next_worker;
      /* become poller */
      pollset->is_iocp_worker = 1;
      g_active_poller = worker;
      gpr_mu_unlock(&grpc_polling_mu);
      grpc_iocp_work(exec_ctx, deadline);
      grpc_exec_ctx_flush(exec_ctx);
      gpr_mu_lock(&grpc_polling_mu);
      pollset->is_iocp_worker = 0;
      g_active_poller = NULL;
      /* try to get a worker from this pollsets worker list */
      next_worker = pop_front_worker(&pollset->root_worker, GRPC_POLLSET_WORKER_LINK_POLLSET);
      /* try to get a worker from the global list */
      next_worker = pop_front_worker(&g_global_root_worker, GRPC_POLLSET_WORKER_LINK_GLOBAL);
      if (next_worker != NULL) {
        next_worker->kicked = 1;
        gpr_cv_signal(&next_worker->cv);
      }

      if (pollset->shutting_down && pollset->on_shutdown != NULL) {
        grpc_exec_ctx_enqueue(exec_ctx, pollset->on_shutdown, 1);
        pollset->on_shutdown = NULL;
      }
      goto done;
    }
    push_front_worker(&g_global_root_worker, GRPC_POLLSET_WORKER_LINK_GLOBAL, worker);
    push_front_worker(&pollset->root_worker, GRPC_POLLSET_WORKER_LINK_POLLSET, worker);
    added_worker = 1;
    while (!worker->kicked) {
      if (gpr_cv_wait(&worker->cv, &grpc_polling_mu, deadline)) {
        break;
      }
    }
  } else {
    pollset->kicked_without_pollers = 0;
  }
done:
  if (!grpc_closure_list_empty(exec_ctx->closure_list)) {
    gpr_mu_unlock(&grpc_polling_mu);
    grpc_exec_ctx_flush(exec_ctx);
    gpr_mu_lock(&grpc_polling_mu);
  }
  if (added_worker) {
    remove_worker(worker, GRPC_POLLSET_WORKER_LINK_GLOBAL);
    remove_worker(worker, GRPC_POLLSET_WORKER_LINK_POLLSET);
  }
  gpr_cv_destroy(&worker->cv);
}

void grpc_pollset_kick(grpc_pollset *p, grpc_pollset_worker *specific_worker) {
  if (specific_worker != NULL) {
    if (specific_worker == GRPC_POLLSET_KICK_BROADCAST) {
      for (specific_worker = p->root_worker.links[GRPC_POLLSET_WORKER_LINK_POLLSET].next;
           specific_worker != &p->root_worker;
           specific_worker = specific_worker->links[GRPC_POLLSET_WORKER_LINK_POLLSET].next) {
        specific_worker->kicked = 1;
        gpr_cv_signal(&specific_worker->cv);
      }
      p->kicked_without_pollers = 1;
      if (p->is_iocp_worker) {
        grpc_iocp_kick();
      }
    } else {
      if (p->is_iocp_worker) {
        if (g_active_poller == specific_worker) {
          grpc_iocp_kick();
        }
      } else {
        specific_worker->kicked = 1;
        gpr_cv_signal(&specific_worker->cv);
      }
    }
  } else {
    specific_worker = pop_front_worker(&p->root_worker, GRPC_POLLSET_WORKER_LINK_POLLSET);
    if (specific_worker != NULL) {
      grpc_pollset_kick(p, specific_worker);
    } else if (p->is_iocp_worker) {
      grpc_iocp_kick();
    } else {
      p->kicked_without_pollers = 1;
    }
  }
}

#endif /* GPR_WINSOCK_SOCKET */