text: /*
   *
   * Copyright 2015-2016, 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/log.h>
  #include <grpc/support/thd.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_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) {
    pollset->shutting_down = 1;
    grpc_pollset_kick(pollset, GRPC_POLLSET_KICK_BROADCAST);
    if (!pollset->is_iocp_worker) {
      grpc_exec_ctx_enqueue(exec_ctx, closure, true, NULL);
    } else {
      pollset->on_shutdown = closure;
    }
  }
  
  void grpc_pollset_destroy(grpc_pollset *pollset) {}
  
  void grpc_pollset_reset(grpc_pollset *pollset) {
    GPR_ASSERT(pollset->shutting_down);
    GPR_ASSERT(
        !has_workers(&pollset->root_worker, GRPC_POLLSET_WORKER_LINK_POLLSET));
    pollset->shutting_down = 0;
    pollset->is_iocp_worker = 0;
    pollset->kicked_without_pollers = 0;
    pollset->on_shutdown = NULL;
  }
  
  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 (!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);
        if (next_worker == NULL) {
          /* 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, true, NULL);
          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 && 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;
      }
    }
  }
  
  void grpc_kick_poller(void) { grpc_iocp_kick(); }
  
  #endif /* GPR_WINSOCK_SOCKET */
  