Merge pull request #9428 from grpc/revert-8842-metadata_filter

Revert "Metadata handling rewrite"

17 files changed, 139 insertions, 167 deletions

diff --git a/src/core/lib/iomgr/closure.c b/src/core/lib/iomgr/closure.c
index 8e4efd3370..da0ec878a3 100644
--- a/src/core/lib/iomgr/closure.c
+++ b/src/core/lib/iomgr/closure.c
@@ -34,7 +34,6 @@
 #include "src/core/lib/iomgr/closure.h"
 
 #include <grpc/support/alloc.h>
-#include <grpc/support/log.h>
 
 #include "src/core/lib/profiling/timers.h"
 
diff --git a/src/core/lib/iomgr/closure.h b/src/core/lib/iomgr/closure.h
index 6748b21e59..ee386fbc76 100644
--- a/src/core/lib/iomgr/closure.h
+++ b/src/core/lib/iomgr/closure.h
@@ -66,7 +66,6 @@ typedef struct grpc_closure_scheduler_vtable {
               grpc_error *error);
   void (*sched)(grpc_exec_ctx *exec_ctx, grpc_closure *closure,
                 grpc_error *error);
-  const char *name;
 } grpc_closure_scheduler_vtable;
 
 /** Abstract type that can schedule closures for execution */
diff --git a/src/core/lib/iomgr/combiner.c b/src/core/lib/iomgr/combiner.c
index ba6c7087a9..c26a73b2b7 100644
--- a/src/core/lib/iomgr/combiner.c
+++ b/src/core/lib/iomgr/combiner.c
@@ -86,17 +86,13 @@ static void combiner_finally_exec_covered(grpc_exec_ctx *exec_ctx,
                                           grpc_error *error);
 
 static const grpc_closure_scheduler_vtable scheduler_uncovered = {
-    combiner_exec_uncovered, combiner_exec_uncovered,
-    "combiner:immediately:uncovered"};
+    combiner_exec_uncovered, combiner_exec_uncovered};
 static const grpc_closure_scheduler_vtable scheduler_covered = {
-    combiner_exec_covered, combiner_exec_covered,
-    "combiner:immediately:covered"};
+    combiner_exec_covered, combiner_exec_covered};
 static const grpc_closure_scheduler_vtable finally_scheduler_uncovered = {
-    combiner_finally_exec_uncovered, combiner_finally_exec_uncovered,
-    "combiner:finally:uncovered"};
+    combiner_finally_exec_uncovered, combiner_finally_exec_uncovered};
 static const grpc_closure_scheduler_vtable finally_scheduler_covered = {
-    combiner_finally_exec_covered, combiner_finally_exec_covered,
-    "combiner:finally:covered"};
+    combiner_finally_exec_covered, combiner_finally_exec_covered};
 
 static void offload(grpc_exec_ctx *exec_ctx, void *arg, grpc_error *error);
 
diff --git a/src/core/lib/iomgr/error.c b/src/core/lib/iomgr/error.c
index dbe5b139f9..f6bb3a0477 100644
--- a/src/core/lib/iomgr/error.c
+++ b/src/core/lib/iomgr/error.c
@@ -33,10 +33,13 @@
 
 #include "src/core/lib/iomgr/error.h"
 
+#include <inttypes.h>
+#include <stdbool.h>
 #include <string.h>
 
 #include <grpc/status.h>
 #include <grpc/support/alloc.h>
+#include <grpc/support/avl.h>
 #include <grpc/support/log.h>
 #include <grpc/support/string_util.h>
 #include <grpc/support/useful.h>
@@ -45,7 +48,6 @@
 #include <grpc/support/log_windows.h>
 #endif
 
-#include "src/core/lib/iomgr/error_internal.h"
 #include "src/core/lib/profiling/timers.h"
 
 static void destroy_integer(void *key) {}
@@ -126,10 +128,6 @@ static const char *error_int_name(grpc_error_ints key) {
 
 static const char *error_str_name(grpc_error_strs key) {
   switch (key) {
-    case GRPC_ERROR_STR_KEY:
-      return "key";
-    case GRPC_ERROR_STR_VALUE:
-      return "value";
     case GRPC_ERROR_STR_DESCRIPTION:
       return "description";
     case GRPC_ERROR_STR_OS_ERROR:
@@ -162,7 +160,16 @@ static const char *error_time_name(grpc_error_times key) {
   GPR_UNREACHABLE_CODE(return "unknown");
 }
 
-bool grpc_error_is_special(grpc_error *err) {
+struct grpc_error {
+  gpr_refcount refs;
+  gpr_avl ints;
+  gpr_avl strs;
+  gpr_avl times;
+  gpr_avl errs;
+  uintptr_t next_err;
+};
+
+static bool is_special(grpc_error *err) {
   return err == GRPC_ERROR_NONE || err == GRPC_ERROR_OOM ||
          err == GRPC_ERROR_CANCELLED;
 }
@@ -170,7 +177,7 @@ bool grpc_error_is_special(grpc_error *err) {
 #ifdef GRPC_ERROR_REFCOUNT_DEBUG
 grpc_error *grpc_error_ref(grpc_error *err, const char *file, int line,
                            const char *func) {
-  if (grpc_error_is_special(err)) return err;
+  if (is_special(err)) return err;
   gpr_log(GPR_DEBUG, "%p: %" PRIdPTR " -> %" PRIdPTR " [%s:%d %s]", err,
           err->refs.count, err->refs.count + 1, file, line, func);
   gpr_ref(&err->refs);
@@ -178,26 +185,25 @@ grpc_error *grpc_error_ref(grpc_error *err, const char *file, int line,
 }
 #else
 grpc_error *grpc_error_ref(grpc_error *err) {
-  if (grpc_error_is_special(err)) return err;
+  if (is_special(err)) return err;
   gpr_ref(&err->refs);
   return err;
 }
 #endif
 
 static void error_destroy(grpc_error *err) {
-  GPR_ASSERT(!grpc_error_is_special(err));
+  GPR_ASSERT(!is_special(err));
   gpr_avl_unref(err->ints);
   gpr_avl_unref(err->strs);
   gpr_avl_unref(err->errs);
   gpr_avl_unref(err->times);
-  gpr_free((void *)gpr_atm_acq_load(&err->error_string));
   gpr_free(err);
 }
 
 #ifdef GRPC_ERROR_REFCOUNT_DEBUG
 void grpc_error_unref(grpc_error *err, const char *file, int line,
                       const char *func) {
-  if (grpc_error_is_special(err)) return;
+  if (is_special(err)) return;
   gpr_log(GPR_DEBUG, "%p: %" PRIdPTR " -> %" PRIdPTR " [%s:%d %s]", err,
           err->refs.count, err->refs.count - 1, file, line, func);
   if (gpr_unref(&err->refs)) {
@@ -206,7 +212,7 @@ void grpc_error_unref(grpc_error *err, const char *file, int line,
 }
 #else
 void grpc_error_unref(grpc_error *err) {
-  if (grpc_error_is_special(err)) return;
+  if (is_special(err)) return;
   if (gpr_unref(&err->refs)) {
     error_destroy(err);
   }
@@ -241,7 +247,6 @@ grpc_error *grpc_error_create(const char *file, int line, const char *desc,
   err->times = gpr_avl_add(gpr_avl_create(&avl_vtable_times),
                            (void *)(uintptr_t)GRPC_ERROR_TIME_CREATED,
                            box_time(gpr_now(GPR_CLOCK_REALTIME)));
-  gpr_atm_no_barrier_store(&err->error_string, 0);
   gpr_ref_init(&err->refs, 1);
   GPR_TIMER_END("grpc_error_create", 0);
   return err;
@@ -250,10 +255,9 @@ grpc_error *grpc_error_create(const char *file, int line, const char *desc,
 static grpc_error *copy_error_and_unref(grpc_error *in) {
   GPR_TIMER_BEGIN("copy_error_and_unref", 0);
   grpc_error *out;
-  if (grpc_error_is_special(in)) {
+  if (is_special(in)) {
     if (in == GRPC_ERROR_NONE)
-      out = grpc_error_set_int(GRPC_ERROR_CREATE("no error"),
-                               GRPC_ERROR_INT_GRPC_STATUS, GRPC_STATUS_OK);
+      out = GRPC_ERROR_CREATE("no error");
     else if (in == GRPC_ERROR_OOM)
       out = GRPC_ERROR_CREATE("oom");
     else if (in == GRPC_ERROR_CANCELLED)
@@ -271,7 +275,6 @@ static grpc_error *copy_error_and_unref(grpc_error *in) {
     out->strs = gpr_avl_ref(in->strs);
     out->errs = gpr_avl_ref(in->errs);
     out->times = gpr_avl_ref(in->times);
-    gpr_atm_no_barrier_store(&out->error_string, 0);
     out->next_err = in->next_err;
     gpr_ref_init(&out->refs, 1);
     GRPC_ERROR_UNREF(in);
@@ -289,29 +292,14 @@ grpc_error *grpc_error_set_int(grpc_error *src, grpc_error_ints which,
   return new;
 }
 
-typedef struct {
-  grpc_error *error;
-  grpc_status_code code;
-  const char *msg;
-} special_error_status_map;
-static special_error_status_map error_status_map[] = {
-    {GRPC_ERROR_NONE, GRPC_STATUS_OK, NULL},
-    {GRPC_ERROR_CANCELLED, GRPC_STATUS_CANCELLED, "Cancelled"},
-    {GRPC_ERROR_OOM, GRPC_STATUS_RESOURCE_EXHAUSTED, "Out of memory"},
-};
-
 bool grpc_error_get_int(grpc_error *err, grpc_error_ints which, intptr_t *p) {
   GPR_TIMER_BEGIN("grpc_error_get_int", 0);
   void *pp;
-  if (grpc_error_is_special(err)) {
-    if (which == GRPC_ERROR_INT_GRPC_STATUS) {
-      for (size_t i = 0; i < GPR_ARRAY_SIZE(error_status_map); i++) {
-        if (error_status_map[i].error == err) {
-          if (p != NULL) *p = error_status_map[i].code;
-          GPR_TIMER_END("grpc_error_get_int", 0);
-          return true;
-        }
-      }
+  if (is_special(err)) {
+    if (err == GRPC_ERROR_CANCELLED && which == GRPC_ERROR_INT_GRPC_STATUS) {
+      *p = GRPC_STATUS_CANCELLED;
+      GPR_TIMER_END("grpc_error_get_int", 0);
+      return true;
     }
     GPR_TIMER_END("grpc_error_get_int", 0);
     return false;
@@ -336,17 +324,66 @@ grpc_error *grpc_error_set_str(grpc_error *src, grpc_error_strs which,
 }
 
 const char *grpc_error_get_str(grpc_error *err, grpc_error_strs which) {
-  if (grpc_error_is_special(err)) {
-    if (which == GRPC_ERROR_STR_GRPC_MESSAGE) {
-      for (size_t i = 0; i < GPR_ARRAY_SIZE(error_status_map); i++) {
-        if (error_status_map[i].error == err) {
-          return error_status_map[i].msg;
-        }
-      }
+  if (is_special(err)) return NULL;
+  return gpr_avl_get(err->strs, (void *)(uintptr_t)which);
+}
+
+typedef struct {
+  grpc_error *error;
+  grpc_status_code code;
+  const char *msg;
+} special_error_status_map;
+static special_error_status_map error_status_map[] = {
+    {GRPC_ERROR_NONE, GRPC_STATUS_OK, ""},
+    {GRPC_ERROR_CANCELLED, GRPC_STATUS_CANCELLED, "RPC cancelled"},
+    {GRPC_ERROR_OOM, GRPC_STATUS_RESOURCE_EXHAUSTED, "Out of memory"},
+};
+
+static grpc_error *recursively_find_error_with_status(grpc_error *error,
+                                                      intptr_t *status) {
+  // If the error itself has a status code, return it.
+  if (grpc_error_get_int(error, GRPC_ERROR_INT_GRPC_STATUS, status)) {
+    return error;
+  }
+  // Otherwise, search through its children.
+  intptr_t key = 0;
+  while (true) {
+    grpc_error *child_error = gpr_avl_get(error->errs, (void *)key++);
+    if (child_error == NULL) break;
+    grpc_error *result =
+        recursively_find_error_with_status(child_error, status);
+    if (result != NULL) return result;
+  }
+  return NULL;
+}
+
+void grpc_error_get_status(grpc_error *error, grpc_status_code *code,
+                           const char **msg) {
+  // Handle special errors via the static map.
+  for (size_t i = 0; i < GPR_ARRAY_SIZE(error_status_map); ++i) {
+    if (error == error_status_map[i].error) {
+      *code = error_status_map[i].code;
+      *msg = error_status_map[i].msg;
+      return;
     }
-    return NULL;
   }
-  return gpr_avl_get(err->strs, (void *)(uintptr_t)which);
+  // Populate code.
+  // Start with the parent error and recurse through the tree of children
+  // until we find the first one that has a status code.
+  intptr_t status = GRPC_STATUS_UNKNOWN;  // Default in case we don't find one.
+  grpc_error *found_error = recursively_find_error_with_status(error, &status);
+  *code = (grpc_status_code)status;
+  // Now populate msg.
+  // If we found an error with a status code above, use that; otherwise,
+  // fall back to using the parent error.
+  if (found_error == NULL) found_error = error;
+  // If the error has a status message, use it.  Otherwise, fall back to
+  // the error description.
+  *msg = grpc_error_get_str(found_error, GRPC_ERROR_STR_GRPC_MESSAGE);
+  if (*msg == NULL) {
+    *msg = grpc_error_get_str(found_error, GRPC_ERROR_STR_DESCRIPTION);
+    if (*msg == NULL) *msg = "uknown error";  // Just in case.
+  }
 }
 
 grpc_error *grpc_error_add_child(grpc_error *src, grpc_error *child) {
@@ -498,6 +535,7 @@ static void add_errs(gpr_avl_node *n, char **s, size_t *sz, size_t *cap,
   *first = false;
   const char *e = grpc_error_string(n->value);
   append_str(e, s, sz, cap);
+  grpc_error_free_string(e);
   add_errs(n->right, s, sz, cap, first);
 }
 
@@ -519,7 +557,7 @@ static int cmp_kvs(const void *a, const void *b) {
   return strcmp(ka->key, kb->key);
 }
 
-static char *finish_kvs(kv_pairs *kvs) {
+static const char *finish_kvs(kv_pairs *kvs) {
   char *s = NULL;
   size_t sz = 0;
   size_t cap = 0;
@@ -540,18 +578,19 @@ static char *finish_kvs(kv_pairs *kvs) {
   return s;
 }
 
+void grpc_error_free_string(const char *str) {
+  if (str == no_error_string) return;
+  if (str == oom_error_string) return;
+  if (str == cancelled_error_string) return;
+  gpr_free((char *)str);
+}
+
 const char *grpc_error_string(grpc_error *err) {
   GPR_TIMER_BEGIN("grpc_error_string", 0);
   if (err == GRPC_ERROR_NONE) return no_error_string;
   if (err == GRPC_ERROR_OOM) return oom_error_string;
   if (err == GRPC_ERROR_CANCELLED) return cancelled_error_string;
 
-  void *p = (void *)gpr_atm_acq_load(&err->error_string);
-  if (p != NULL) {
-    GPR_TIMER_END("grpc_error_string", 0);
-    return p;
-  }
-
   kv_pairs kvs;
   memset(&kvs, 0, sizeof(kvs));
 
@@ -564,13 +603,7 @@ const char *grpc_error_string(grpc_error *err) {
 
   qsort(kvs.kvs, kvs.num_kvs, sizeof(kv_pair), cmp_kvs);
 
-  char *out = finish_kvs(&kvs);
-
-  if (!gpr_atm_rel_cas(&err->error_string, 0, (gpr_atm)out)) {
-    gpr_free(out);
-    out = (char *)gpr_atm_no_barrier_load(&err->error_string);
-  }
-
+  const char *out = finish_kvs(&kvs);
   GPR_TIMER_END("grpc_error_string", 0);
   return out;
 }
@@ -605,6 +638,7 @@ bool grpc_log_if_error(const char *what, grpc_error *error, const char *file,
   if (error == GRPC_ERROR_NONE) return true;
   const char *msg = grpc_error_string(error);
   gpr_log(file, line, GPR_LOG_SEVERITY_ERROR, "%s: %s", what, msg);
+  grpc_error_free_string(msg);
   GRPC_ERROR_UNREF(error);
   return false;
 }
diff --git a/src/core/lib/iomgr/error.h b/src/core/lib/iomgr/error.h
index ffacdac393..f3f3b80a09 100644
--- a/src/core/lib/iomgr/error.h
+++ b/src/core/lib/iomgr/error.h
@@ -124,11 +124,7 @@ typedef enum {
   /// filename that we were trying to read/write when this error occurred
   GRPC_ERROR_STR_FILENAME,
   /// which data was queued for writing when the error occurred
-  GRPC_ERROR_STR_QUEUED_BUFFERS,
-  /// key associated with the error
-  GRPC_ERROR_STR_KEY,
-  /// value associated with the error
-  GRPC_ERROR_STR_VALUE,
+  GRPC_ERROR_STR_QUEUED_BUFFERS
 } grpc_error_strs;
 
 typedef enum {
@@ -145,6 +141,7 @@ typedef enum {
 #define GRPC_ERROR_CANCELLED ((grpc_error *)4)
 
 const char *grpc_error_string(grpc_error *error);
+void grpc_error_free_string(const char *str);
 
 /// Create an error - but use GRPC_ERROR_CREATE instead
 grpc_error *grpc_error_create(const char *file, int line, const char *desc,
@@ -192,6 +189,12 @@ grpc_error *grpc_error_set_str(grpc_error *src, grpc_error_strs which,
 /// Caller does NOT own return value.
 const char *grpc_error_get_str(grpc_error *error, grpc_error_strs which);
 
+/// A utility function to get the status code and message to be returned
+/// to the application.  If not set in the top-level message, looks
+/// through child errors until it finds the first one with these attributes.
+void grpc_error_get_status(grpc_error *error, grpc_status_code *code,
+                           const char **msg);
+
 /// Add a child error: an error that is believed to have contributed to this
 /// error occurring. Allows root causing high level errors from lower level
 /// errors that contributed to them.
diff --git a/src/core/lib/iomgr/error_internal.h b/src/core/lib/iomgr/error_internal.h
deleted file mode 100644
index 1c89ead4ed..0000000000
--- a/src/core/lib/iomgr/error_internal.h
+++ /dev/null
@@ -1,54 +0,0 @@
-/*
- *
- * Copyright 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.
- *
- */
-
-#ifndef GRPC_CORE_LIB_IOMGR_ERROR_INTERNAL_H
-#define GRPC_CORE_LIB_IOMGR_ERROR_INTERNAL_H
-
-#include <inttypes.h>
-#include <stdbool.h>
-
-#include <grpc/support/avl.h>
-
-struct grpc_error {
-  gpr_refcount refs;
-  gpr_avl ints;
-  gpr_avl strs;
-  gpr_avl times;
-  gpr_avl errs;
-  uintptr_t next_err;
-  gpr_atm error_string;
-};
-
-bool grpc_error_is_special(grpc_error *err);
-
-#endif /* GRPC_CORE_LIB_IOMGR_ERROR_INTERNAL_H */
diff --git a/src/core/lib/iomgr/ev_epoll_linux.c b/src/core/lib/iomgr/ev_epoll_linux.c
index 39b5c0032e..d6664aead2 100644
--- a/src/core/lib/iomgr/ev_epoll_linux.c
+++ b/src/core/lib/iomgr/ev_epoll_linux.c
@@ -321,7 +321,7 @@ gpr_atm g_epoll_sync;
 #endif /* defined(GRPC_TSAN) */
 
 static const grpc_closure_scheduler_vtable workqueue_scheduler_vtable = {
-    workqueue_enqueue, workqueue_enqueue, "workqueue"};
+    workqueue_enqueue, workqueue_enqueue};
 
 static void pi_add_ref(polling_island *pi);
 static void pi_unref(grpc_exec_ctx *exec_ctx, polling_island *pi);
diff --git a/src/core/lib/iomgr/ev_posix.c b/src/core/lib/iomgr/ev_posix.c
index c106ba5400..2975d619e1 100644
--- a/src/core/lib/iomgr/ev_posix.c
+++ b/src/core/lib/iomgr/ev_posix.c
@@ -52,8 +52,6 @@
  *  tests */
 grpc_poll_function_type grpc_poll_function = poll;
 
-grpc_wakeup_fd grpc_global_wakeup_fd;
-
 static const grpc_event_engine_vtable *g_event_engine;
 static const char *g_poll_strategy_name = NULL;
 
diff --git a/src/core/lib/iomgr/exec_ctx.c b/src/core/lib/iomgr/exec_ctx.c
index 83bb436bd0..6aa788f8e5 100644
--- a/src/core/lib/iomgr/exec_ctx.c
+++ b/src/core/lib/iomgr/exec_ctx.c
@@ -42,16 +42,11 @@
 #include "src/core/lib/profiling/timers.h"
 
 bool grpc_exec_ctx_ready_to_finish(grpc_exec_ctx *exec_ctx) {
-  if ((exec_ctx->flags & GRPC_EXEC_CTX_FLAG_IS_FINISHED) == 0) {
-    if (exec_ctx->check_ready_to_finish(exec_ctx,
-                                        exec_ctx->check_ready_to_finish_arg)) {
-      exec_ctx->flags |= GRPC_EXEC_CTX_FLAG_IS_FINISHED;
-      return true;
-    }
-    return false;
-  } else {
-    return true;
+  if (!exec_ctx->cached_ready_to_finish) {
+    exec_ctx->cached_ready_to_finish = exec_ctx->check_ready_to_finish(
+        exec_ctx, exec_ctx->check_ready_to_finish_arg);
   }
+  return exec_ctx->cached_ready_to_finish;
 }
 
 bool grpc_never_ready_to_finish(grpc_exec_ctx *exec_ctx, void *arg_ignored) {
@@ -87,7 +82,7 @@ bool grpc_exec_ctx_flush(grpc_exec_ctx *exec_ctx) {
 }
 
 void grpc_exec_ctx_finish(grpc_exec_ctx *exec_ctx) {
-  exec_ctx->flags |= GRPC_EXEC_CTX_FLAG_IS_FINISHED;
+  exec_ctx->cached_ready_to_finish = true;
   grpc_exec_ctx_flush(exec_ctx);
 }
 
@@ -106,6 +101,6 @@ void grpc_exec_ctx_global_init(void) {}
 void grpc_exec_ctx_global_shutdown(void) {}
 
 static const grpc_closure_scheduler_vtable exec_ctx_scheduler_vtable = {
-    exec_ctx_run, exec_ctx_sched, "exec_ctx"};
+    exec_ctx_run, exec_ctx_sched};
 static grpc_closure_scheduler exec_ctx_scheduler = {&exec_ctx_scheduler_vtable};
 grpc_closure_scheduler *grpc_schedule_on_exec_ctx = &exec_ctx_scheduler;
diff --git a/src/core/lib/iomgr/exec_ctx.h b/src/core/lib/iomgr/exec_ctx.h
index f99a0fee5f..e566f1b3e8 100644
--- a/src/core/lib/iomgr/exec_ctx.h
+++ b/src/core/lib/iomgr/exec_ctx.h
@@ -43,13 +43,6 @@
 typedef struct grpc_workqueue grpc_workqueue;
 typedef struct grpc_combiner grpc_combiner;
 
-/* This exec_ctx is ready to return: either pre-populated, or cached as soon as
-   the finish_check returns true */
-#define GRPC_EXEC_CTX_FLAG_IS_FINISHED 1
-/* The exec_ctx's thread is (potentially) owned by a call or channel: care
-   should be given to not delete said call/channel from this exec_ctx */
-#define GRPC_EXEC_CTX_FLAG_THREAD_RESOURCE_LOOP 2
-
 /** Execution context.
  *  A bag of data that collects information along a callstack.
  *  Generally created at public API entry points, and passed down as
@@ -70,26 +63,36 @@ typedef struct grpc_combiner grpc_combiner;
  *  - Instances are always passed as the first argument to a function that
  *    takes it, and always as a pointer (grpc_exec_ctx is never copied).
  */
+#ifndef GRPC_EXECUTION_CONTEXT_SANITIZER
 struct grpc_exec_ctx {
   grpc_closure_list closure_list;
   /** currently active combiner: updated only via combiner.c */
   grpc_combiner *active_combiner;
   /** last active combiner in the active combiner list */
   grpc_combiner *last_combiner;
-  uintptr_t flags;
+  bool cached_ready_to_finish;
   void *check_ready_to_finish_arg;
   bool (*check_ready_to_finish)(grpc_exec_ctx *exec_ctx, void *arg);
 };
 
 /* initializer for grpc_exec_ctx:
    prefer to use GRPC_EXEC_CTX_INIT whenever possible */
-#define GRPC_EXEC_CTX_INITIALIZER(flags, finish_check, finish_check_arg) \
-  { GRPC_CLOSURE_LIST_INIT, NULL, NULL, flags, finish_check_arg, finish_check }
+#define GRPC_EXEC_CTX_INIT_WITH_FINISH_CHECK(finish_check, finish_check_arg) \
+  { GRPC_CLOSURE_LIST_INIT, NULL, NULL, false, finish_check_arg, finish_check }
+#else
+struct grpc_exec_ctx {
+  bool cached_ready_to_finish;
+  void *check_ready_to_finish_arg;
+  bool (*check_ready_to_finish)(grpc_exec_ctx *exec_ctx, void *arg);
+};
+#define GRPC_EXEC_CTX_INIT_WITH_FINISH_CHECK(finish_check, finish_check_arg) \
+  { false, finish_check_arg, finish_check }
+#endif
 
 /* initialize an execution context at the top level of an API call into grpc
    (this is safe to use elsewhere, though possibly not as efficient) */
 #define GRPC_EXEC_CTX_INIT \
-  GRPC_EXEC_CTX_INITIALIZER(GRPC_EXEC_CTX_FLAG_IS_FINISHED, NULL, NULL)
+  GRPC_EXEC_CTX_INIT_WITH_FINISH_CHECK(grpc_always_ready_to_finish, NULL)
 
 extern grpc_closure_scheduler *grpc_schedule_on_exec_ctx;
 
diff --git a/src/core/lib/iomgr/executor.c b/src/core/lib/iomgr/executor.c
index a5b62aa888..852775564f 100644
--- a/src/core/lib/iomgr/executor.c
+++ b/src/core/lib/iomgr/executor.c
@@ -158,7 +158,7 @@ void grpc_executor_shutdown(grpc_exec_ctx *exec_ctx) {
   gpr_mu_destroy(&g_executor.mu);
 }
 
-static const grpc_closure_scheduler_vtable executor_vtable = {
-    executor_push, executor_push, "executor"};
+static const grpc_closure_scheduler_vtable executor_vtable = {executor_push,
+                                                              executor_push};
 static grpc_closure_scheduler executor_scheduler = {&executor_vtable};
 grpc_closure_scheduler *grpc_executor_scheduler = &executor_scheduler;
diff --git a/src/core/lib/iomgr/load_file.c b/src/core/lib/iomgr/load_file.c
index f40c8b28cc..217bc5da59 100644
--- a/src/core/lib/iomgr/load_file.c
+++ b/src/core/lib/iomgr/load_file.c
@@ -47,7 +47,7 @@ grpc_error *grpc_load_file(const char *filename, int add_null_terminator,
                            grpc_slice *output) {
   unsigned char *contents = NULL;
   size_t contents_size = 0;
-  grpc_slice result = grpc_empty_slice();
+  grpc_slice result = gpr_empty_slice();
   FILE *file;
   size_t bytes_read = 0;
   grpc_error *error = GRPC_ERROR_NONE;
diff --git a/src/core/lib/iomgr/resource_quota.c b/src/core/lib/iomgr/resource_quota.c
index 41ea609c73..31590cd53b 100644
--- a/src/core/lib/iomgr/resource_quota.c
+++ b/src/core/lib/iomgr/resource_quota.c
@@ -378,15 +378,11 @@ static void ru_slice_unref(grpc_exec_ctx *exec_ctx, void *p) {
   }
 }
 
-static const grpc_slice_refcount_vtable ru_slice_vtable = {
-    ru_slice_ref, ru_slice_unref, grpc_slice_default_eq_impl,
-    grpc_slice_default_hash_impl};
-
 static grpc_slice ru_slice_create(grpc_resource_user *resource_user,
                                   size_t size) {
   ru_slice_refcount *rc = gpr_malloc(sizeof(ru_slice_refcount) + size);
-  rc->base.vtable = &ru_slice_vtable;
-  rc->base.sub_refcount = &rc->base;
+  rc->base.ref = ru_slice_ref;
+  rc->base.unref = ru_slice_unref;
   gpr_ref_init(&rc->refs, 1);
   rc->resource_user = resource_user;
   rc->size = size;
diff --git a/src/core/lib/iomgr/tcp_client_posix.c b/src/core/lib/iomgr/tcp_client_posix.c
index 16b0f4e73c..9a77c92016 100644
--- a/src/core/lib/iomgr/tcp_client_posix.c
+++ b/src/core/lib/iomgr/tcp_client_posix.c
@@ -118,6 +118,7 @@ static void tc_on_alarm(grpc_exec_ctx *exec_ctx, void *acp, grpc_error *error) {
     const char *str = grpc_error_string(error);
     gpr_log(GPR_DEBUG, "CLIENT_CONNECT: %s: on_alarm: error=%s", ac->addr_str,
             str);
+    grpc_error_free_string(str);
   }
   gpr_mu_lock(&ac->mu);
   if (ac->fd != NULL) {
@@ -177,6 +178,7 @@ static void on_writable(grpc_exec_ctx *exec_ctx, void *acp, grpc_error *error) {
     const char *str = grpc_error_string(error);
     gpr_log(GPR_DEBUG, "CLIENT_CONNECT: %s: on_writable: error=%s",
             ac->addr_str, str);
+    grpc_error_free_string(str);
   }
 
   gpr_mu_lock(&ac->mu);
diff --git a/src/core/lib/iomgr/tcp_posix.c b/src/core/lib/iomgr/tcp_posix.c
index a33e63e845..ece44978b0 100644
--- a/src/core/lib/iomgr/tcp_posix.c
+++ b/src/core/lib/iomgr/tcp_posix.c
@@ -181,7 +181,7 @@ static void call_read_cb(grpc_exec_ctx *exec_ctx, grpc_tcp *tcp,
     size_t i;
     const char *str = grpc_error_string(error);
     gpr_log(GPR_DEBUG, "read: error=%s", str);
-
+    grpc_error_free_string(str);
     for (i = 0; i < tcp->incoming_buffer->count; i++) {
       char *dump = grpc_dump_slice(tcp->incoming_buffer->slices[i],
                                    GPR_DUMP_HEX | GPR_DUMP_ASCII);
@@ -435,6 +435,7 @@ static void tcp_handle_write(grpc_exec_ctx *exec_ctx, void *arg /* grpc_tcp */,
     if (grpc_tcp_trace) {
       const char *str = grpc_error_string(error);
       gpr_log(GPR_DEBUG, "write: %s", str);
+      grpc_error_free_string(str);
     }
 
     grpc_closure_run(exec_ctx, cb, error);
@@ -484,6 +485,7 @@ static void tcp_write(grpc_exec_ctx *exec_ctx, grpc_endpoint *ep,
     if (grpc_tcp_trace) {
       const char *str = grpc_error_string(error);
       gpr_log(GPR_DEBUG, "write: %s", str);
+      grpc_error_free_string(str);
     }
     grpc_closure_sched(exec_ctx, cb, error);
   }
diff --git a/src/core/lib/iomgr/tcp_server_windows.c b/src/core/lib/iomgr/tcp_server_windows.c
index bd4b9b2df1..dafe851ce8 100644
--- a/src/core/lib/iomgr/tcp_server_windows.c
+++ b/src/core/lib/iomgr/tcp_server_windows.c
@@ -343,7 +343,7 @@ static void on_accept(grpc_exec_ctx *exec_ctx, void *arg, grpc_error *error) {
   if (error != GRPC_ERROR_NONE) {
     const char *msg = grpc_error_string(error);
     gpr_log(GPR_INFO, "Skipping on_accept due to error: %s", msg);
-
+    grpc_error_free_string(msg);
     gpr_mu_unlock(&sp->server->mu);
     return;
   }
diff --git a/src/core/lib/iomgr/tcp_uv.c b/src/core/lib/iomgr/tcp_uv.c
index 7f4ea49a1c..3ddc79706b 100644
--- a/src/core/lib/iomgr/tcp_uv.c
+++ b/src/core/lib/iomgr/tcp_uv.c
@@ -48,7 +48,6 @@
 #include "src/core/lib/iomgr/network_status_tracker.h"
 #include "src/core/lib/iomgr/resource_quota.h"
 #include "src/core/lib/iomgr/tcp_uv.h"
-#include "src/core/lib/slice/slice_internal.h"
 #include "src/core/lib/slice/slice_string_helpers.h"
 #include "src/core/lib/support/string.h"
 
@@ -157,7 +156,7 @@ static void read_callback(uv_stream_t *stream, ssize_t nread,
       size_t i;
       const char *str = grpc_error_string(error);
       gpr_log(GPR_DEBUG, "read: error=%s", str);
-
+      grpc_error_free_string(str);
       for (i = 0; i < tcp->read_slices->count; i++) {
         char *dump = grpc_dump_slice(tcp->read_slices->slices[i],
                                      GPR_DUMP_HEX | GPR_DUMP_ASCII);