Merge branch 'can-we-be-single-threaded' of github.com:ctiller/grpc into pfft

src/core/iomgr/iocp_windows.c

@@ -50,13 +50,28 @@
 static ULONG g_iocp_kick_token;
 static OVERLAPPED g_iocp_custom_overlap;
 
-static gpr_event g_shutdown_iocp;
-static gpr_event g_iocp_done;
 static gpr_atm g_custom_events = 0;
 
 static HANDLE g_iocp;
 
-static void do_iocp_work(grpc_exec_ctx *exec_ctx) {
+static DWORD deadline_to_millis_timeout(gpr_timespec deadline,
+                                        gpr_timespec now) {
+  gpr_timespec timeout;
+  static const int max_spin_polling_us = 10;
+  if (gpr_time_cmp(deadline, gpr_inf_future(deadline.clock_type)) == 0) {
+    return INFINITE;
+  }
+  if (gpr_time_cmp(deadline, gpr_time_add(now, gpr_time_from_micros(
+    max_spin_polling_us,
+    GPR_TIMESPAN))) <= 0) {
+    return 0;
+  }
+  timeout = gpr_time_sub(deadline, now);
+  return gpr_time_to_millis(gpr_time_add(
+    timeout, gpr_time_from_nanos(GPR_NS_PER_SEC - 1, GPR_TIMESPAN)));
+}
+
+void grpc_iocp_work(grpc_exec_ctx *exec_ctx, gpr_timespec deadline) {
   BOOL success;
   DWORD bytes = 0;
   DWORD flags = 0;
@@ -66,10 +81,10 @@ static void do_iocp_work(grpc_exec_ctx *exec_ctx) {
   grpc_winsocket_callback_info *info;
   grpc_closure *closure = NULL;
   success = GetQueuedCompletionStatus(g_iocp, &bytes, &completion_key,
-                                      &overlapped, INFINITE);
-  /* success = 0 and overlapped = NULL means the deadline got attained.
-     Which is impossible. since our wait time is +inf */
-  GPR_ASSERT(success || overlapped);
+                                      &overlapped, deadline_to_millis_timeout(deadline, gpr_now(deadline.clock_type)));
+  if (success == 0 && overlapped == NULL) {
+    return;
+  }
   GPR_ASSERT(completion_key && overlapped);
   if (overlapped == &g_iocp_custom_overlap) {
     gpr_atm_full_fetch_add(&g_custom_events, -1);
@@ -109,29 +124,10 @@ static void do_iocp_work(grpc_exec_ctx *exec_ctx) {
   }
 }
 
-static void iocp_loop(void *p) {
-  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-
-  while (gpr_atm_acq_load(&g_custom_events) ||
-         !gpr_event_get(&g_shutdown_iocp)) {
-    do_iocp_work(&exec_ctx);
-    grpc_exec_ctx_flush(&exec_ctx);
-  }
-  grpc_exec_ctx_finish(&exec_ctx);
-
-  gpr_event_set(&g_iocp_done, (void *)1);
-}
-
 void grpc_iocp_init(void) {
-  gpr_thd_id id;
-
   g_iocp =
       CreateIoCompletionPort(INVALID_HANDLE_VALUE, NULL, (ULONG_PTR)NULL, 0);
   GPR_ASSERT(g_iocp);
-
-  gpr_event_init(&g_iocp_done);
-  gpr_event_init(&g_shutdown_iocp);
-  gpr_thd_new(&id, iocp_loop, NULL, NULL);
 }
 
 void grpc_iocp_kick(void) {
@@ -144,12 +140,13 @@ void grpc_iocp_kick(void) {
 }
 
 void grpc_iocp_shutdown(void) {
-  BOOL success;
-  gpr_event_set(&g_shutdown_iocp, (void *)1);
-  grpc_iocp_kick();
-  gpr_event_wait(&g_iocp_done, gpr_inf_future(GPR_CLOCK_REALTIME));
-  success = CloseHandle(g_iocp);
-  GPR_ASSERT(success);
+  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
+  while (gpr_atm_acq_load(&g_custom_events)) {
+    grpc_iocp_work(&exec_ctx, gpr_inf_future(GPR_CLOCK_MONOTONIC));
+    grpc_exec_ctx_flush(&exec_ctx);
+  }
+  grpc_exec_ctx_finish(&exec_ctx);
+  GPR_ASSERT(CloseHandle(g_iocp));
 }
 
 void grpc_iocp_add_socket(grpc_winsocket *socket) {

src/core/iomgr/iocp_windows.h

@@ -38,6 +38,7 @@
 
 #include "src/core/iomgr/socket_windows.h"
 
+void grpc_iocp_work(grpc_exec_ctx *exec_ctx, gpr_timespec deadline);
 void grpc_iocp_init(void);
 void grpc_iocp_kick(void);
 void grpc_iocp_shutdown(void);

src/core/iomgr/iomgr.c

@@ -59,6 +59,7 @@ void grpc_iomgr_init(void) {
   g_root_object.next = g_root_object.prev = &g_root_object;
   g_root_object.name = "root";
   grpc_iomgr_platform_init();
+  grpc_pollset_global_init();
 }
 
 static size_t count_objects(void) {
@@ -128,6 +129,7 @@ void grpc_iomgr_shutdown(void) {
   gpr_mu_lock(&g_mu);
   gpr_mu_unlock(&g_mu);
 
+  grpc_pollset_global_shutdown();
   grpc_iomgr_platform_shutdown();
   gpr_mu_destroy(&g_mu);
   gpr_cv_destroy(&g_rcv);

src/core/iomgr/iomgr_internal.h

@@ -43,6 +43,9 @@ typedef struct grpc_iomgr_object {
   struct grpc_iomgr_object *prev;
 } grpc_iomgr_object;
 
+void grpc_pollset_global_init(void);
+void grpc_pollset_global_shutdown(void);
+
 void grpc_iomgr_register_object(grpc_iomgr_object *obj, const char *name);
 void grpc_iomgr_unregister_object(grpc_iomgr_object *obj);
 

src/core/iomgr/iomgr_posix.c

@@ -42,12 +42,10 @@
 
 void grpc_iomgr_platform_init(void) {
   grpc_fd_global_init();
-  grpc_pollset_global_init();
   grpc_register_tracer("tcp", &grpc_tcp_trace);
 }
 
 void grpc_iomgr_platform_shutdown(void) {
-  grpc_pollset_global_shutdown();
   grpc_fd_global_shutdown();
 }
 

src/core/iomgr/iomgr_posix.h

@@ -36,7 +36,4 @@
 
 #include "src/core/iomgr/iomgr_internal.h"
 
-void grpc_pollset_global_init(void);
-void grpc_pollset_global_shutdown(void);
-
 #endif /* GRPC_INTERNAL_CORE_IOMGR_IOMGR_POSIX_H */

src/core/iomgr/pollset_windows.c

@@ -39,38 +39,66 @@
 
 #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"
 
-static void remove_worker(grpc_pollset *p, grpc_pollset_worker *worker) {
-  worker->prev->next = worker->next;
-  worker->next->prev = worker->prev;
+static gpr_mu g_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(&g_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(&g_polling_mu);
 }
 
-static int has_workers(grpc_pollset *p) {
-  return p->root_worker.next != &p->root_worker;
+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 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);
+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 *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_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 *p, grpc_pollset_worker *worker) {
-  worker->prev = &p->root_worker;
-  worker->next = worker->prev->next;
-  worker->prev->next = worker->next->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
@@ -81,8 +109,9 @@ static void push_front_worker(grpc_pollset *p, grpc_pollset_worker *worker) {
 void grpc_pollset_init(grpc_pollset *pollset) {
   memset(pollset, 0, sizeof(*pollset));
   gpr_mu_init(&pollset->mu);
-  pollset->root_worker.next = pollset->root_worker.prev = &pollset->root_worker;
-  pollset->kicked_without_pollers = 0;
+  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,
@@ -90,8 +119,12 @@ void grpc_pollset_shutdown(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
   gpr_mu_lock(&pollset->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(&pollset->mu);
-  grpc_exec_ctx_enqueue(exec_ctx, closure, 1);
 }
 
 void grpc_pollset_destroy(grpc_pollset *pollset) {
@@ -102,13 +135,42 @@ 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->next = worker->prev = NULL;
+  worker->links[GRPC_POLLSET_WORKER_LINK_POLLSET].next = 
+    worker->links[GRPC_POLLSET_WORKER_LINK_POLLSET].prev = 
+    NULL;
   gpr_cv_init(&worker->cv);
   if (grpc_alarm_check(exec_ctx, now, &deadline)) {
     goto done;
   }
   if (!pollset->kicked_without_pollers && !pollset->shutting_down) {
-    push_front_worker(pollset, worker);
+    gpr_mu_lock(&g_polling_mu);
+    if (g_active_poller == NULL) {
+      grpc_pollset_worker *next_worker;
+      /* become poller */
+      pollset->is_iocp_worker = 1;
+      g_active_poller = worker;
+      gpr_mu_unlock(&g_polling_mu);
+      gpr_mu_unlock(&pollset->mu);
+      grpc_iocp_work(exec_ctx, deadline);
+      gpr_mu_lock(&pollset->mu);
+      gpr_mu_lock(&g_polling_mu);
+      pollset->is_iocp_worker = 0;
+      g_active_poller = NULL;
+      next_worker = pop_front_worker(&g_global_root_worker, GRPC_POLLSET_WORKER_LINK_GLOBAL);
+      if (next_worker != NULL) {
+        gpr_cv_signal(&next_worker->cv);
+      }
+      gpr_mu_unlock(&g_polling_mu);
+
+      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);
+    gpr_mu_unlock(&g_polling_mu);
+    push_front_worker(&pollset->root_worker, GRPC_POLLSET_WORKER_LINK_POLLSET, worker);
     added_worker = 1;
     gpr_cv_wait(&worker->cv, &pollset->mu, deadline);
   } else {
@@ -122,27 +184,40 @@ done:
   }
   gpr_cv_destroy(&worker->cv);
   if (added_worker) {
-    remove_worker(pollset, worker);
+    remove_worker(worker, GRPC_POLLSET_WORKER_LINK_GLOBAL);
+    remove_worker(worker, GRPC_POLLSET_WORKER_LINK_POLLSET);
   }
 }
 
 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;
+      for (specific_worker = p->root_worker.links[GRPC_POLLSET_WORKER_LINK_POLLSET].next;
            specific_worker != &p->root_worker;
-           specific_worker = specific_worker->next) {
+           specific_worker = specific_worker->links[GRPC_POLLSET_WORKER_LINK_POLLSET].next) {
         gpr_cv_signal(&specific_worker->cv);
       }
       p->kicked_without_pollers = 1;
+      if (p->is_iocp_worker) {
+        grpc_iocp_kick();
+      }
     } else {
-      gpr_cv_signal(&specific_worker->cv);
+      if (p->is_iocp_worker) {
+        gpr_mu_lock(&g_polling_mu);
+        if (g_active_poller == specific_worker) {
+          grpc_iocp_kick();
+        }
+        gpr_mu_unlock(&g_polling_mu);
+      } else {
+        gpr_cv_signal(&specific_worker->cv);
+      }
     }
   } else {
-    specific_worker = pop_front_worker(p);
+    specific_worker = pop_front_worker(&p->root_worker, GRPC_POLLSET_WORKER_LINK_POLLSET);
     if (specific_worker != NULL) {
-      push_back_worker(p, specific_worker);
-      gpr_cv_signal(&specific_worker->cv);
+      grpc_pollset_kick(p, specific_worker);
+    } else if (p->is_iocp_worker) {
+      grpc_iocp_kick();
     } else {
       p->kicked_without_pollers = 1;
     }

src/core/iomgr/pollset_windows.h

@@ -43,17 +43,29 @@
    used to synchronize with the IOCP, and workers are condition variables
    used to block threads until work is ready. */
 
-typedef struct grpc_pollset_worker {
-  gpr_cv cv;
+typedef enum {
+  GRPC_POLLSET_WORKER_LINK_POLLSET = 0,
+  GRPC_POLLSET_WORKER_LINK_GLOBAL,
+  GRPC_POLLSET_WORKER_LINK_TYPES
+} grpc_pollset_worker_link_type;
+
+typedef struct grpc_pollset_worker_link {
   struct grpc_pollset_worker *next;
   struct grpc_pollset_worker *prev;
+} grpc_pollset_worker_link;
+
+typedef struct grpc_pollset_worker {
+  gpr_cv cv;
+  grpc_pollset_worker_link links[GRPC_POLLSET_WORKER_LINK_TYPES];
 } grpc_pollset_worker;
 
 typedef struct grpc_pollset {
   gpr_mu mu;
   int shutting_down;
   int kicked_without_pollers;
+  int is_iocp_worker;
   grpc_pollset_worker root_worker;
+  grpc_closure *on_shutdown;
 } grpc_pollset;
 
 #define GRPC_POLLSET_MU(pollset) (&(pollset)->mu)