Revert "move recv_trailing_metadata into its own callback, don't use on_complete for recv_ops"

7 files changed, 49 insertions, 166 deletions

diff --git a/src/core/lib/channel/connected_channel.cc b/src/core/lib/channel/connected_channel.cc
index e2ea334ded..ddd3029402 100644
--- a/src/core/lib/channel/connected_channel.cc
+++ b/src/core/lib/channel/connected_channel.cc
@@ -51,7 +51,6 @@ typedef struct connected_channel_call_data {
   callback_state on_complete[6];  // Max number of pending batches.
   callback_state recv_initial_metadata_ready;
   callback_state recv_message_ready;
-  callback_state recv_trailing_metadata_ready;
 } call_data;
 
 static void run_in_call_combiner(void* arg, grpc_error* error) {
@@ -112,12 +111,6 @@ static void con_start_transport_stream_op_batch(
     intercept_callback(calld, state, false, "recv_message_ready",
                        &batch->payload->recv_message.recv_message_ready);
   }
-  if (batch->recv_trailing_metadata) {
-    callback_state* state = &calld->recv_trailing_metadata_ready;
-    intercept_callback(
-        calld, state, false, "recv_trailing_metadata_ready",
-        &batch->payload->recv_trailing_metadata.recv_trailing_metadata_ready);
-  }
   if (batch->cancel_stream) {
     // There can be more than one cancellation batch in flight at any
     // given time, so we can't just pick out a fixed index into
@@ -128,7 +121,7 @@ static void con_start_transport_stream_op_batch(
         static_cast<callback_state*>(gpr_malloc(sizeof(*state)));
     intercept_callback(calld, state, true, "on_complete (cancel_stream)",
                        &batch->on_complete);
-  } else if (batch->on_complete != nullptr) {
+  } else {
     callback_state* state = get_state_for_batch(calld, batch);
     intercept_callback(calld, state, false, "on_complete", &batch->on_complete);
   }
diff --git a/src/core/lib/iomgr/call_combiner.h b/src/core/lib/iomgr/call_combiner.h
index f9ce29f231..0ccd08ea57 100644
--- a/src/core/lib/iomgr/call_combiner.h
+++ b/src/core/lib/iomgr/call_combiner.h
@@ -26,7 +26,6 @@
 #include <grpc/support/atm.h>
 
 #include "src/core/lib/gpr/mpscq.h"
-#include "src/core/lib/gprpp/inlined_vector.h"
 #include "src/core/lib/iomgr/closure.h"
 
 // A simple, lock-free mechanism for serializing activity related to a
@@ -110,83 +109,4 @@ void grpc_call_combiner_set_notify_on_cancel(grpc_call_combiner* call_combiner,
 void grpc_call_combiner_cancel(grpc_call_combiner* call_combiner,
                                grpc_error* error);
 
-namespace grpc_core {
-
-// Helper for running a list of closures in a call combiner.
-//
-// Each callback running in the call combiner will eventually be
-// returned to the surface, at which point the surface will yield the
-// call combiner.  So when we are running in the call combiner and have
-// more than one callback to return to the surface, we need to re-enter
-// the call combiner for all but one of those callbacks.
-class CallCombinerClosureList {
- public:
-  CallCombinerClosureList() {}
-
-  // Adds a closure to the list.  The closure must eventually result in
-  // the call combiner being yielded.
-  void Add(grpc_closure* closure, grpc_error* error, const char* reason) {
-    closures_.emplace_back(closure, error, reason);
-  }
-
-  // Runs all closures in the call combiner and yields the call combiner.
-  //
-  // All but one of the closures in the list will be scheduled via
-  // GRPC_CALL_COMBINER_START(), and the remaining closure will be
-  // scheduled via GRPC_CLOSURE_SCHED(), which will eventually result in
-  // yielding the call combiner.  If the list is empty, then the call
-  // combiner will be yielded immediately.
-  void RunClosures(grpc_call_combiner* call_combiner) {
-    for (size_t i = 1; i < closures_.size(); ++i) {
-      auto& closure = closures_[i];
-      GRPC_CALL_COMBINER_START(call_combiner, closure.closure, closure.error,
-                               closure.reason);
-    }
-    if (closures_.size() > 0) {
-      if (grpc_call_combiner_trace.enabled()) {
-        gpr_log(GPR_INFO,
-                "CallCombinerClosureList executing closure while already "
-                "holding call_combiner %p: closure=%p error=%s reason=%s",
-                call_combiner, closures_[0].closure,
-                grpc_error_string(closures_[0].error), closures_[0].reason);
-      }
-      // This will release the call combiner.
-      GRPC_CLOSURE_SCHED(closures_[0].closure, closures_[0].error);
-    } else {
-      GRPC_CALL_COMBINER_STOP(call_combiner, "no closures to schedule");
-    }
-    closures_.clear();
-  }
-
-  // Runs all closures in the call combiner, but does NOT yield the call
-  // combiner.  All closures will be scheduled via GRPC_CALL_COMBINER_START().
-  void RunClosuresWithoutYielding(grpc_call_combiner* call_combiner) {
-    for (size_t i = 0; i < closures_.size(); ++i) {
-      auto& closure = closures_[i];
-      GRPC_CALL_COMBINER_START(call_combiner, closure.closure, closure.error,
-                               closure.reason);
-    }
-    closures_.clear();
-  }
-
-  size_t size() const { return closures_.size(); }
-
- private:
-  struct CallCombinerClosure {
-    grpc_closure* closure;
-    grpc_error* error;
-    const char* reason;
-
-    CallCombinerClosure(grpc_closure* closure, grpc_error* error,
-                        const char* reason)
-        : closure(closure), error(error), reason(reason) {}
-  };
-
-  // There are generally a maximum of 6 closures to run in the call
-  // combiner, one for each pending op.
-  InlinedVector<CallCombinerClosure, 6> closures_;
-};
-
-}  // namespace grpc_core
-
 #endif /* GRPC_CORE_LIB_IOMGR_CALL_COMBINER_H */
diff --git a/src/core/lib/iomgr/closure.h b/src/core/lib/iomgr/closure.h
index f14c723844..34a494485d 100644
--- a/src/core/lib/iomgr/closure.h
+++ b/src/core/lib/iomgr/closure.h
@@ -283,10 +283,9 @@ inline void grpc_closure_sched(grpc_closure* c, grpc_error* error) {
     if (c->scheduled) {
       gpr_log(GPR_ERROR,
               "Closure already scheduled. (closure: %p, created: [%s:%d], "
-              "previously scheduled at: [%s: %d], newly scheduled at [%s: %d], "
-              "run?: %s",
+              "previously scheduled at: [%s: %d] run?: %s",
               c, c->file_created, c->line_created, c->file_initiated,
-              c->line_initiated, file, line, c->run ? "true" : "false");
+              c->line_initiated, c->run ? "true" : "false");
       abort();
     }
     c->scheduled = true;
diff --git a/src/core/lib/surface/call.cc b/src/core/lib/surface/call.cc
index d44846cd12..1cf8ea94e7 100644
--- a/src/core/lib/surface/call.cc
+++ b/src/core/lib/surface/call.cc
@@ -233,7 +233,6 @@ struct grpc_call {
   grpc_closure receiving_slice_ready;
   grpc_closure receiving_stream_ready;
   grpc_closure receiving_initial_metadata_ready;
-  grpc_closure receiving_trailing_metadata_ready;
   uint32_t test_only_last_message_flags;
 
   grpc_closure release_call;
@@ -1210,6 +1209,7 @@ static void post_batch_completion(batch_control* bctl) {
 
   if (bctl->op.send_initial_metadata) {
     grpc_metadata_batch_destroy(
+
         &call->metadata_batch[0 /* is_receiving */][0 /* is_trailing */]);
   }
   if (bctl->op.send_message) {
@@ -1217,9 +1217,14 @@ static void post_batch_completion(batch_control* bctl) {
   }
   if (bctl->op.send_trailing_metadata) {
     grpc_metadata_batch_destroy(
+
         &call->metadata_batch[0 /* is_receiving */][1 /* is_trailing */]);
   }
   if (bctl->op.recv_trailing_metadata) {
+    grpc_metadata_batch* md =
+        &call->metadata_batch[1 /* is_receiving */][1 /* is_trailing */];
+    recv_trailing_filter(call, md);
+
     /* propagate cancellation to any interested children */
     gpr_atm_rel_store(&call->received_final_op_atm, 1);
     parent_call* pc = get_parent_call(call);
@@ -1241,6 +1246,7 @@ static void post_batch_completion(batch_control* bctl) {
       }
       gpr_mu_unlock(&pc->child_list_mu);
     }
+
     if (call->is_client) {
       get_final_status(call, set_status_value_directly,
                        call->final_op.client.status,
@@ -1250,6 +1256,7 @@ static void post_batch_completion(batch_control* bctl) {
       get_final_status(call, set_cancelled_value,
                        call->final_op.server.cancelled, nullptr, nullptr);
     }
+
     GRPC_ERROR_UNREF(error);
     error = GRPC_ERROR_NONE;
   }
@@ -1531,19 +1538,6 @@ static void receiving_initial_metadata_ready(void* bctlp, grpc_error* error) {
   finish_batch_step(bctl);
 }
 
-static void receiving_trailing_metadata_ready(void* bctlp, grpc_error* error) {
-  batch_control* bctl = static_cast<batch_control*>(bctlp);
-  grpc_call* call = bctl->call;
-  GRPC_CALL_COMBINER_STOP(&call->call_combiner, "recv_trailing_metadata_ready");
-  add_batch_error(bctl, GRPC_ERROR_REF(error), false);
-  if (error == GRPC_ERROR_NONE) {
-    grpc_metadata_batch* md =
-        &call->metadata_batch[1 /* is_receiving */][1 /* is_trailing */];
-    recv_trailing_filter(call, md);
-  }
-  finish_batch_step(bctl);
-}
-
 static void finish_batch(void* bctlp, grpc_error* error) {
   batch_control* bctl = static_cast<batch_control*>(bctlp);
   grpc_call* call = bctl->call;
@@ -1564,8 +1558,7 @@ static grpc_call_error call_start_batch(grpc_call* call, const grpc_op* ops,
   size_t i;
   const grpc_op* op;
   batch_control* bctl;
-  bool has_send_ops = false;
-  int num_recv_ops = 0;
+  int num_completion_callbacks_needed = 1;
   grpc_call_error error = GRPC_CALL_OK;
   grpc_transport_stream_op_batch* stream_op;
   grpc_transport_stream_op_batch_payload* stream_op_payload;
@@ -1671,7 +1664,6 @@ static grpc_call_error call_start_batch(grpc_call* call, const grpc_op* ops,
           stream_op_payload->send_initial_metadata.peer_string =
               &call->peer_string;
         }
-        has_send_ops = true;
         break;
       }
       case GRPC_OP_SEND_MESSAGE: {
@@ -1701,7 +1693,6 @@ static grpc_call_error call_start_batch(grpc_call* call, const grpc_op* ops,
             &op->data.send_message.send_message->data.raw.slice_buffer, flags);
         stream_op_payload->send_message.send_message.reset(
             call->sending_stream.get());
-        has_send_ops = true;
         break;
       }
       case GRPC_OP_SEND_CLOSE_FROM_CLIENT: {
@@ -1722,7 +1713,6 @@ static grpc_call_error call_start_batch(grpc_call* call, const grpc_op* ops,
         call->sent_final_op = true;
         stream_op_payload->send_trailing_metadata.send_trailing_metadata =
             &call->metadata_batch[0 /* is_receiving */][1 /* is_trailing */];
-        has_send_ops = true;
         break;
       }
       case GRPC_OP_SEND_STATUS_FROM_SERVER: {
@@ -1787,7 +1777,6 @@ static grpc_call_error call_start_batch(grpc_call* call, const grpc_op* ops,
         }
         stream_op_payload->send_trailing_metadata.send_trailing_metadata =
             &call->metadata_batch[0 /* is_receiving */][1 /* is_trailing */];
-        has_send_ops = true;
         break;
       }
       case GRPC_OP_RECV_INITIAL_METADATA: {
@@ -1815,7 +1804,7 @@ static grpc_call_error call_start_batch(grpc_call* call, const grpc_op* ops,
           stream_op_payload->recv_initial_metadata.peer_string =
               &call->peer_string;
         }
-        ++num_recv_ops;
+        num_completion_callbacks_needed++;
         break;
       }
       case GRPC_OP_RECV_MESSAGE: {
@@ -1837,7 +1826,7 @@ static grpc_call_error call_start_batch(grpc_call* call, const grpc_op* ops,
                           grpc_schedule_on_exec_ctx);
         stream_op_payload->recv_message.recv_message_ready =
             &call->receiving_stream_ready;
-        ++num_recv_ops;
+        num_completion_callbacks_needed++;
         break;
       }
       case GRPC_OP_RECV_STATUS_ON_CLIENT: {
@@ -1863,16 +1852,11 @@ static grpc_call_error call_start_batch(grpc_call* call, const grpc_op* ops,
         call->final_op.client.error_string =
             op->data.recv_status_on_client.error_string;
         stream_op->recv_trailing_metadata = true;
+        stream_op->collect_stats = true;
         stream_op_payload->recv_trailing_metadata.recv_trailing_metadata =
             &call->metadata_batch[1 /* is_receiving */][1 /* is_trailing */];
-        stream_op_payload->recv_trailing_metadata.collect_stats =
+        stream_op_payload->collect_stats.collect_stats =
             &call->final_info.stats.transport_stream_stats;
-        GRPC_CLOSURE_INIT(&call->receiving_trailing_metadata_ready,
-                          receiving_trailing_metadata_ready, bctl,
-                          grpc_schedule_on_exec_ctx);
-        stream_op_payload->recv_trailing_metadata.recv_trailing_metadata_ready =
-            &call->receiving_trailing_metadata_ready;
-        ++num_recv_ops;
         break;
       }
       case GRPC_OP_RECV_CLOSE_ON_SERVER: {
@@ -1893,16 +1877,11 @@ static grpc_call_error call_start_batch(grpc_call* call, const grpc_op* ops,
         call->final_op.server.cancelled =
             op->data.recv_close_on_server.cancelled;
         stream_op->recv_trailing_metadata = true;
+        stream_op->collect_stats = true;
         stream_op_payload->recv_trailing_metadata.recv_trailing_metadata =
             &call->metadata_batch[1 /* is_receiving */][1 /* is_trailing */];
-        stream_op_payload->recv_trailing_metadata.collect_stats =
+        stream_op_payload->collect_stats.collect_stats =
             &call->final_info.stats.transport_stream_stats;
-        GRPC_CLOSURE_INIT(&call->receiving_trailing_metadata_ready,
-                          receiving_trailing_metadata_ready, bctl,
-                          grpc_schedule_on_exec_ctx);
-        stream_op_payload->recv_trailing_metadata.recv_trailing_metadata_ready =
-            &call->receiving_trailing_metadata_ready;
-        ++num_recv_ops;
         break;
       }
     }
@@ -1912,15 +1891,13 @@ static grpc_call_error call_start_batch(grpc_call* call, const grpc_op* ops,
   if (!is_notify_tag_closure) {
     GPR_ASSERT(grpc_cq_begin_op(call->cq, notify_tag));
   }
-  gpr_ref_init(&bctl->steps_to_complete, (has_send_ops ? 1 : 0) + num_recv_ops);
-
-  if (has_send_ops) {
-    GRPC_CLOSURE_INIT(&bctl->finish_batch, finish_batch, bctl,
-                      grpc_schedule_on_exec_ctx);
-    stream_op->on_complete = &bctl->finish_batch;
-  }
+  gpr_ref_init(&bctl->steps_to_complete, num_completion_callbacks_needed);
 
+  GRPC_CLOSURE_INIT(&bctl->finish_batch, finish_batch, bctl,
+                    grpc_schedule_on_exec_ctx);
+  stream_op->on_complete = &bctl->finish_batch;
   gpr_atm_rel_store(&call->any_ops_sent_atm, 1);
+
   execute_batch(call, stream_op, &bctl->start_batch);
 
 done:
diff --git a/src/core/lib/transport/transport.cc b/src/core/lib/transport/transport.cc
index cbdb77c844..039d603394 100644
--- a/src/core/lib/transport/transport.cc
+++ b/src/core/lib/transport/transport.cc
@@ -212,32 +212,21 @@ void grpc_transport_stream_op_batch_finish_with_failure(
   if (batch->send_message) {
     batch->payload->send_message.send_message.reset();
   }
-  if (batch->cancel_stream) {
-    GRPC_ERROR_UNREF(batch->payload->cancel_stream.cancel_error);
+  if (batch->recv_message) {
+    GRPC_CALL_COMBINER_START(
+        call_combiner, batch->payload->recv_message.recv_message_ready,
+        GRPC_ERROR_REF(error), "failing recv_message_ready");
   }
-  // Construct a list of closures to execute.
-  grpc_core::CallCombinerClosureList closures;
   if (batch->recv_initial_metadata) {
-    closures.Add(
+    GRPC_CALL_COMBINER_START(
+        call_combiner,
         batch->payload->recv_initial_metadata.recv_initial_metadata_ready,
         GRPC_ERROR_REF(error), "failing recv_initial_metadata_ready");
   }
-  if (batch->recv_message) {
-    closures.Add(batch->payload->recv_message.recv_message_ready,
-                 GRPC_ERROR_REF(error), "failing recv_message_ready");
-  }
-  if (batch->recv_trailing_metadata) {
-    closures.Add(
-        batch->payload->recv_trailing_metadata.recv_trailing_metadata_ready,
-        GRPC_ERROR_REF(error), "failing recv_trailing_metadata_ready");
-  }
-  if (batch->on_complete != nullptr) {
-    closures.Add(batch->on_complete, GRPC_ERROR_REF(error),
-                 "failing on_complete");
+  GRPC_CLOSURE_SCHED(batch->on_complete, error);
+  if (batch->cancel_stream) {
+    GRPC_ERROR_UNREF(batch->payload->cancel_stream.cancel_error);
   }
-  // Execute closures.
-  closures.RunClosures(call_combiner);
-  GRPC_ERROR_UNREF(error);
 }
 
 typedef struct {
diff --git a/src/core/lib/transport/transport.h b/src/core/lib/transport/transport.h
index 585b9dfae9..b2e252d939 100644
--- a/src/core/lib/transport/transport.h
+++ b/src/core/lib/transport/transport.h
@@ -122,15 +122,9 @@ typedef struct grpc_transport_stream_op_batch_payload
 /* Transport stream op: a set of operations to perform on a transport
    against a single stream */
 typedef struct grpc_transport_stream_op_batch {
-  /** Should be scheduled when all of the non-recv operations in the batch
-      are complete.
-
-      The recv ops (recv_initial_metadata, recv_message, and
-      recv_trailing_metadata) each have their own callbacks.  If a batch
-      contains both recv ops and non-recv ops, on_complete should be
-      scheduled as soon as the non-recv ops are complete, regardless of
-      whether or not the recv ops are complete.  If a batch contains
-      only recv ops, on_complete can be null. */
+  /** Should be enqueued when all requested operations (excluding recv_message
+      and recv_initial_metadata which have their own closures) in a given batch
+      have been completed. */
   grpc_closure* on_complete;
 
   /** Values for the stream op (fields set are determined by flags above) */
@@ -155,6 +149,9 @@ typedef struct grpc_transport_stream_op_batch {
    */
   bool recv_trailing_metadata : 1;
 
+  /** Collect any stats into provided buffer, zero internal stat counters */
+  bool collect_stats : 1;
+
   /** Cancel this stream with the provided error */
   bool cancel_stream : 1;
 
@@ -222,11 +219,12 @@ struct grpc_transport_stream_op_batch_payload {
 
   struct {
     grpc_metadata_batch* recv_trailing_metadata;
-    grpc_transport_stream_stats* collect_stats;
-    /** Should be enqueued when initial metadata is ready to be processed. */
-    grpc_closure* recv_trailing_metadata_ready;
   } recv_trailing_metadata;
 
+  struct {
+    grpc_transport_stream_stats* collect_stats;
+  } collect_stats;
+
   /** Forcefully close this stream.
       The HTTP2 semantics should be:
       - server side: if cancel_error has GRPC_ERROR_INT_GRPC_STATUS, and
diff --git a/src/core/lib/transport/transport_op_string.cc b/src/core/lib/transport/transport_op_string.cc
index 8c7db642a5..25ab492f3a 100644
--- a/src/core/lib/transport/transport_op_string.cc
+++ b/src/core/lib/transport/transport_op_string.cc
@@ -120,6 +120,13 @@ char* grpc_transport_stream_op_batch_string(
     gpr_strvec_add(&b, tmp);
   }
 
+  if (op->collect_stats) {
+    gpr_strvec_add(&b, gpr_strdup(" "));
+    gpr_asprintf(&tmp, "COLLECT_STATS:%p",
+                 op->payload->collect_stats.collect_stats);
+    gpr_strvec_add(&b, tmp);
+  }
+
   out = gpr_strvec_flatten(&b, nullptr);
   gpr_strvec_destroy(&b);