Implement new pollset semantics for Windows

src/core/iomgr/pollset_windows.c

@@ -42,6 +42,38 @@
 #include "src/core/iomgr/pollset.h"
 #include "src/core/iomgr/pollset_windows.h"
 
+static void remove_worker(grpc_pollset *p, grpc_pollset_worker *worker) {
+  worker->prev->next = worker->next;
+  worker->next->prev = worker->prev;
+}
+
+static int has_workers(grpc_pollset *p) {
+  return p->root_worker.next != &p->root_worker;
+}
+
+static grpc_pollset_worker *pop_front_worker(grpc_pollset *p) {
+  if (has_workers(p)) {
+    grpc_pollset_worker *w = p->root_worker.next;
+    remove_worker(p, w);
+    return w;
+  }
+  else {
+    return NULL;
+  }
+}
+
+static void push_back_worker(grpc_pollset *p, grpc_pollset_worker *worker) {
+  worker->next = &p->root_worker;
+  worker->prev = worker->next->prev;
+  worker->prev->next = worker->next->prev = worker;
+}
+
+static void push_front_worker(grpc_pollset *p, grpc_pollset_worker *worker) {
+  worker->prev = &p->root_worker;
+  worker->next = worker->prev->next;
+  worker->prev->next = worker->next->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
@@ -50,7 +82,8 @@
 void grpc_pollset_init(grpc_pollset *pollset) {
   memset(pollset, 0, sizeof(*pollset));
   gpr_mu_init(&pollset->mu);
-  gpr_cv_init(&pollset->cv);
+  pollset->root_worker.next = pollset->root_worker.prev = &pollset->root_worker;
+  pollset->kicked_without_pollers = 0;
 }
 
 void grpc_pollset_shutdown(grpc_pollset *pollset,
@@ -58,34 +91,66 @@ void grpc_pollset_shutdown(grpc_pollset *pollset,
                            void *shutdown_done_arg) {
   gpr_mu_lock(&pollset->mu);
   pollset->shutting_down = 1;
-  gpr_cv_broadcast(&pollset->cv);
+  grpc_pollset_kick(pollset, GRPC_POLLSET_KICK_BROADCAST);
   gpr_mu_unlock(&pollset->mu);
   shutdown_done(shutdown_done_arg);
 }
 
 void grpc_pollset_destroy(grpc_pollset *pollset) {
   gpr_mu_destroy(&pollset->mu);
-  gpr_cv_destroy(&pollset->cv);
 }
 
-int grpc_pollset_work(grpc_pollset *pollset, gpr_timespec deadline) {
+int grpc_pollset_work(grpc_pollset *pollset, grpc_pollset_worker *worker, gpr_timespec deadline) {
   gpr_timespec now;
+  int added_worker = 0;
   now = gpr_now(GPR_CLOCK_MONOTONIC);
   if (gpr_time_cmp(now, deadline) > 0) {
     return 0 /* GPR_FALSE */;
   }
+  worker->next = worker->prev = NULL;
+  gpr_cv_init(&worker->cv);
   if (grpc_maybe_call_delayed_callbacks(&pollset->mu, 1 /* GPR_TRUE */)) {
-    return 1 /* GPR_TRUE */;
+    goto done;
   }
   if (grpc_alarm_check(&pollset->mu, now, &deadline)) {
-    return 1 /* GPR_TRUE */;
+    goto done;
   }
-  if (!pollset->shutting_down) {
-    gpr_cv_wait(&pollset->cv, &pollset->mu, deadline);
+  if (!pollset->kicked_without_pollers && !pollset->shutting_down) {
+    push_front_worker(pollset, worker);
+    added_worker = 1;
+    gpr_cv_wait(&worker->cv, &pollset->mu, deadline);
+  } else {
+    pollset->kicked_without_pollers = 0;
+  }
+done:
+  gpr_cv_destroy(&worker->cv);
+  if (added_worker) {
+    remove_worker(pollset, worker);
   }
   return 1 /* GPR_TRUE */;
 }
 
-void grpc_pollset_kick(grpc_pollset *p) { gpr_cv_signal(&p->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.next;
+        specific_worker != &p->root_worker;
+        specific_worker = specific_worker->next) {
+        gpr_cv_signal(&specific_worker->cv);
+      }
+      p->kicked_without_pollers = 1;
+    } else {
+      gpr_cv_signal(&specific_worker->cv);
+    }
+  } else {
+    specific_worker = pop_front_worker(p);
+    if (specific_worker != NULL) {
+      push_back_worker(p, specific_worker);
+      gpr_cv_signal(&specific_worker->cv);
+    } else {
+      p->kicked_without_pollers = 1;
+    }
+  }
+}
 
 #endif /* GPR_WINSOCK_SOCKET */

src/core/iomgr/pollset_windows.h

@@ -42,10 +42,17 @@
    nature of the IO completion ports. A Windows "pollset" is merely a mutex
    and a condition variable, used to synchronize with the IOCP. */
 
+typedef struct grpc_pollset_worker {
+  gpr_cv cv;
+  struct grpc_pollset_worker *next;
+  struct grpc_pollset_worker *prev;
+} grpc_pollset_worker;
+
 typedef struct grpc_pollset {
   gpr_mu mu;
-  gpr_cv cv;
   int shutting_down;
+  int kicked_without_pollers;
+  grpc_pollset_worker root_worker;
 } grpc_pollset;
 
 #define GRPC_POLLSET_MU(pollset) (&(pollset)->mu)