Merge branch 'master' into threadnames

24 files changed, 456 insertions, 300 deletions

diff --git a/src/core/lib/support/arena.h b/src/core/lib/support/arena.h
index 4d43c56bb9..cfe973a036 100644
--- a/src/core/lib/support/arena.h
+++ b/src/core/lib/support/arena.h
@@ -27,10 +27,6 @@
 
 #include <stddef.h>
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 typedef struct gpr_arena gpr_arena;
 
 // Create an arena, with \a initial_size bytes in the first allocated buffer
@@ -40,8 +36,4 @@ void* gpr_arena_alloc(gpr_arena* arena, size_t size);
 // Destroy an arena, returning the total number of bytes allocated
 size_t gpr_arena_destroy(gpr_arena* arena);
 
-#ifdef __cplusplus
-}
-#endif
-
 #endif /* GRPC_CORE_LIB_SUPPORT_ARENA_H */
diff --git a/src/core/lib/support/debug_location.h b/src/core/lib/support/debug_location.h
new file mode 100644
index 0000000000..0939da595d
--- /dev/null
+++ b/src/core/lib/support/debug_location.h
@@ -0,0 +1,52 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_SUPPORT_DEBUG_LOCATION_H
+#define GRPC_CORE_LIB_SUPPORT_DEBUG_LOCATION_H
+
+namespace grpc_core {
+
+// Used for tracking file and line where a call is made for debug builds.
+// No-op for non-debug builds.
+// Callers can use the DEBUG_LOCATION macro in either case.
+#ifndef NDEBUG
+class DebugLocation {
+ public:
+  DebugLocation(const char* file, int line) : file_(file), line_(line) {}
+  bool Log() const { return true; }
+  const char* file() const { return file_; }
+  int line() const { return line_; }
+
+ private:
+  const char* file_;
+  const int line_;
+};
+#define DEBUG_LOCATION DebugLocation(__FILE__, __LINE__)
+#else
+class DebugLocation {
+ public:
+  bool Log() const { return false; }
+  const char* file() const { return nullptr; }
+  int line() const { return -1; }
+};
+#define DEBUG_LOCATION DebugLocation()
+#endif
+
+}  // namespace grpc_core
+
+#endif /* GRPC_CORE_LIB_SUPPORT_DEBUG_LOCATION_H */
diff --git a/src/core/lib/support/env.h b/src/core/lib/support/env.h
index f50d7bcb7a..2452fd330d 100644
--- a/src/core/lib/support/env.h
+++ b/src/core/lib/support/env.h
@@ -21,10 +21,6 @@
 
 #include <stdio.h>
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 /* Env utility functions */
 
 /* Gets the environment variable value with the specified name.
@@ -42,8 +38,4 @@ void gpr_setenv(const char* name, const char* value);
    level of logging. So DO NOT USE THIS. */
 const char* gpr_getenv_silent(const char* name, char** dst);
 
-#ifdef __cplusplus
-}
-#endif
-
 #endif /* GRPC_CORE_LIB_SUPPORT_ENV_H */
diff --git a/src/core/lib/support/fork.cc b/src/core/lib/support/fork.cc
new file mode 100644
index 0000000000..d59ca5584c
--- /dev/null
+++ b/src/core/lib/support/fork.cc
@@ -0,0 +1,62 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include "src/core/lib/support/fork.h"
+
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/useful.h>
+
+#include "src/core/lib/support/env.h"
+
+/*
+ * NOTE: FORKING IS NOT GENERALLY SUPPORTED, THIS IS ONLY INTENDED TO WORK
+ *       AROUND VERY SPECIFIC USE CASES.
+ */
+
+static int override_fork_support_enabled = -1;
+static int fork_support_enabled;
+
+void grpc_fork_support_init() {
+#ifdef GRPC_ENABLE_FORK_SUPPORT
+  fork_support_enabled = 1;
+#else
+  fork_support_enabled = 0;
+  char* env = gpr_getenv("GRPC_ENABLE_FORK_SUPPORT");
+  if (env != NULL) {
+    static const char* truthy[] = {"yes",  "Yes",  "YES", "true",
+                                   "True", "TRUE", "1"};
+    for (size_t i = 0; i < GPR_ARRAY_SIZE(truthy); i++) {
+      if (0 == strcmp(env, truthy[i])) {
+        fork_support_enabled = 1;
+      }
+    }
+    gpr_free(env);
+  }
+#endif
+  if (override_fork_support_enabled != -1) {
+    fork_support_enabled = override_fork_support_enabled;
+  }
+}
+
+int grpc_fork_support_enabled() { return fork_support_enabled; }
+
+void grpc_enable_fork_support(int enable) {
+  override_fork_support_enabled = enable;
+}
diff --git a/src/core/lib/support/fork.h b/src/core/lib/support/fork.h
new file mode 100644
index 0000000000..215d4214a6
--- /dev/null
+++ b/src/core/lib/support/fork.h
@@ -0,0 +1,35 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_SUPPORT_FORK_H
+#define GRPC_CORE_LIB_SUPPORT_FORK_H
+
+/*
+ * NOTE: FORKING IS NOT GENERALLY SUPPORTED, THIS IS ONLY INTENDED TO WORK
+ *       AROUND VERY SPECIFIC USE CASES.
+ */
+
+void grpc_fork_support_init(void);
+
+int grpc_fork_support_enabled(void);
+
+// Test only:  Must be called before grpc_init(), and overrides
+// environment variables/compile flags
+void grpc_enable_fork_support(int enable);
+
+#endif /* GRPC_CORE_LIB_SUPPORT_FORK_H */
diff --git a/src/core/lib/support/histogram.cc b/src/core/lib/support/histogram.cc
deleted file mode 100644
index 73c821a28b..0000000000
--- a/src/core/lib/support/histogram.cc
+++ /dev/null
@@ -1,227 +0,0 @@
-/*
- *
- * Copyright 2015 gRPC authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-#include <grpc/support/histogram.h>
-
-#include <math.h>
-#include <stddef.h>
-#include <string.h>
-
-#include <grpc/support/alloc.h>
-#include <grpc/support/log.h>
-#include <grpc/support/port_platform.h>
-#include <grpc/support/useful.h>
-
-/* Histograms are stored with exponentially increasing bucket sizes.
-   The first bucket is [0, m) where m = 1 + resolution
-   Bucket n (n>=1) contains [m**n, m**(n+1))
-   There are sufficient buckets to reach max_bucket_start */
-
-struct gpr_histogram {
-  /* Sum of all values seen so far */
-  double sum;
-  /* Sum of squares of all values seen so far */
-  double sum_of_squares;
-  /* number of values seen so far */
-  double count;
-  /* m in the description */
-  double multiplier;
-  double one_on_log_multiplier;
-  /* minimum value seen */
-  double min_seen;
-  /* maximum value seen */
-  double max_seen;
-  /* maximum representable value */
-  double max_possible;
-  /* number of buckets */
-  size_t num_buckets;
-  /* the buckets themselves */
-  uint32_t* buckets;
-};
-
-/* determine a bucket index given a value - does no bounds checking */
-static size_t bucket_for_unchecked(gpr_histogram* h, double x) {
-  return (size_t)(log(x) * h->one_on_log_multiplier);
-}
-
-/* bounds checked version of the above */
-static size_t bucket_for(gpr_histogram* h, double x) {
-  size_t bucket = bucket_for_unchecked(h, GPR_CLAMP(x, 1.0, h->max_possible));
-  GPR_ASSERT(bucket < h->num_buckets);
-  return bucket;
-}
-
-/* at what value does a bucket start? */
-static double bucket_start(gpr_histogram* h, double x) {
-  return pow(h->multiplier, x);
-}
-
-gpr_histogram* gpr_histogram_create(double resolution,
-                                    double max_bucket_start) {
-  gpr_histogram* h = (gpr_histogram*)gpr_malloc(sizeof(gpr_histogram));
-  GPR_ASSERT(resolution > 0.0);
-  GPR_ASSERT(max_bucket_start > resolution);
-  h->sum = 0.0;
-  h->sum_of_squares = 0.0;
-  h->multiplier = 1.0 + resolution;
-  h->one_on_log_multiplier = 1.0 / log(1.0 + resolution);
-  h->max_possible = max_bucket_start;
-  h->count = 0.0;
-  h->min_seen = max_bucket_start;
-  h->max_seen = 0.0;
-  h->num_buckets = bucket_for_unchecked(h, max_bucket_start) + 1;
-  GPR_ASSERT(h->num_buckets > 1);
-  GPR_ASSERT(h->num_buckets < 100000000);
-  h->buckets = (uint32_t*)gpr_zalloc(sizeof(uint32_t) * h->num_buckets);
-  return h;
-}
-
-void gpr_histogram_destroy(gpr_histogram* h) {
-  gpr_free(h->buckets);
-  gpr_free(h);
-}
-
-void gpr_histogram_add(gpr_histogram* h, double x) {
-  h->sum += x;
-  h->sum_of_squares += x * x;
-  h->count++;
-  if (x < h->min_seen) {
-    h->min_seen = x;
-  }
-  if (x > h->max_seen) {
-    h->max_seen = x;
-  }
-  h->buckets[bucket_for(h, x)]++;
-}
-
-int gpr_histogram_merge(gpr_histogram* dst, const gpr_histogram* src) {
-  if ((dst->num_buckets != src->num_buckets) ||
-      (dst->multiplier != src->multiplier)) {
-    /* Fail because these histograms don't match */
-    return 0;
-  }
-  gpr_histogram_merge_contents(dst, src->buckets, src->num_buckets,
-                               src->min_seen, src->max_seen, src->sum,
-                               src->sum_of_squares, src->count);
-  return 1;
-}
-
-void gpr_histogram_merge_contents(gpr_histogram* dst, const uint32_t* data,
-                                  size_t data_count, double min_seen,
-                                  double max_seen, double sum,
-                                  double sum_of_squares, double count) {
-  size_t i;
-  GPR_ASSERT(dst->num_buckets == data_count);
-  dst->sum += sum;
-  dst->sum_of_squares += sum_of_squares;
-  dst->count += count;
-  if (min_seen < dst->min_seen) {
-    dst->min_seen = min_seen;
-  }
-  if (max_seen > dst->max_seen) {
-    dst->max_seen = max_seen;
-  }
-  for (i = 0; i < dst->num_buckets; i++) {
-    dst->buckets[i] += data[i];
-  }
-}
-
-static double threshold_for_count_below(gpr_histogram* h, double count_below) {
-  double count_so_far;
-  double lower_bound;
-  double upper_bound;
-  size_t lower_idx;
-  size_t upper_idx;
-
-  if (h->count == 0) {
-    return 0.0;
-  }
-
-  if (count_below <= 0) {
-    return h->min_seen;
-  }
-  if (count_below >= h->count) {
-    return h->max_seen;
-  }
-
-  /* find the lowest bucket that gets us above count_below */
-  count_so_far = 0.0;
-  for (lower_idx = 0; lower_idx < h->num_buckets; lower_idx++) {
-    count_so_far += h->buckets[lower_idx];
-    if (count_so_far >= count_below) {
-      break;
-    }
-  }
-  if (count_so_far == count_below) {
-    /* this bucket hits the threshold exactly... we should be midway through
-       any run of zero values following the bucket */
-    for (upper_idx = lower_idx + 1; upper_idx < h->num_buckets; upper_idx++) {
-      if (h->buckets[upper_idx]) {
-        break;
-      }
-    }
-    return (bucket_start(h, (double)lower_idx) +
-            bucket_start(h, (double)upper_idx)) /
-           2.0;
-  } else {
-    /* treat values as uniform throughout the bucket, and find where this value
-       should lie */
-    lower_bound = bucket_start(h, (double)lower_idx);
-    upper_bound = bucket_start(h, (double)(lower_idx + 1));
-    return GPR_CLAMP(upper_bound - (upper_bound - lower_bound) *
-                                       (count_so_far - count_below) /
-                                       h->buckets[lower_idx],
-                     h->min_seen, h->max_seen);
-  }
-}
-
-double gpr_histogram_percentile(gpr_histogram* h, double percentile) {
-  return threshold_for_count_below(h, h->count * percentile / 100.0);
-}
-
-double gpr_histogram_mean(gpr_histogram* h) {
-  GPR_ASSERT(h->count != 0);
-  return h->sum / h->count;
-}
-
-double gpr_histogram_stddev(gpr_histogram* h) {
-  return sqrt(gpr_histogram_variance(h));
-}
-
-double gpr_histogram_variance(gpr_histogram* h) {
-  if (h->count == 0) return 0.0;
-  return (h->sum_of_squares * h->count - h->sum * h->sum) /
-         (h->count * h->count);
-}
-
-double gpr_histogram_maximum(gpr_histogram* h) { return h->max_seen; }
-
-double gpr_histogram_minimum(gpr_histogram* h) { return h->min_seen; }
-
-double gpr_histogram_count(gpr_histogram* h) { return h->count; }
-
-double gpr_histogram_sum(gpr_histogram* h) { return h->sum; }
-
-double gpr_histogram_sum_of_squares(gpr_histogram* h) {
-  return h->sum_of_squares;
-}
-
-const uint32_t* gpr_histogram_get_contents(gpr_histogram* h, size_t* size) {
-  *size = h->num_buckets;
-  return h->buckets;
-}
diff --git a/src/core/lib/support/log.cc b/src/core/lib/support/log.cc
index e9adc6c349..2a40745e97 100644
--- a/src/core/lib/support/log.cc
+++ b/src/core/lib/support/log.cc
@@ -27,7 +27,7 @@
 #include <stdio.h>
 #include <string.h>
 
-extern "C" void gpr_default_log(gpr_log_func_args* args);
+void gpr_default_log(gpr_log_func_args* args);
 static gpr_atm g_log_func = (gpr_atm)gpr_default_log;
 static gpr_atm g_min_severity_to_print = GPR_LOG_VERBOSITY_UNSET;
 
diff --git a/src/core/lib/support/log_android.cc b/src/core/lib/support/log_android.cc
index 73d24cd84d..0d3ac0fe52 100644
--- a/src/core/lib/support/log_android.cc
+++ b/src/core/lib/support/log_android.cc
@@ -39,8 +39,8 @@ static android_LogPriority severity_to_log_priority(gpr_log_severity severity) {
   return ANDROID_LOG_DEFAULT;
 }
 
-extern "C" void gpr_log(const char* file, int line, gpr_log_severity severity,
-                        const char* format, ...) {
+void gpr_log(const char* file, int line, gpr_log_severity severity,
+             const char* format, ...) {
   char* message = NULL;
   va_list args;
   va_start(args, format);
@@ -50,7 +50,7 @@ extern "C" void gpr_log(const char* file, int line, gpr_log_severity severity,
   free(message);
 }
 
-extern "C" void gpr_default_log(gpr_log_func_args* args) {
+void gpr_default_log(gpr_log_func_args* args) {
   const char* final_slash;
   const char* display_file;
   char* output = NULL;
diff --git a/src/core/lib/support/log_linux.cc b/src/core/lib/support/log_linux.cc
index e0e277fe87..6b1f1c71e4 100644
--- a/src/core/lib/support/log_linux.cc
+++ b/src/core/lib/support/log_linux.cc
@@ -56,7 +56,7 @@ void gpr_log(const char* file, int line, gpr_log_severity severity,
   free(message);
 }
 
-extern "C" void gpr_default_log(gpr_log_func_args* args) {
+void gpr_default_log(gpr_log_func_args* args) {
   const char* final_slash;
   char* prefix;
   const char* display_file;
diff --git a/src/core/lib/support/log_posix.cc b/src/core/lib/support/log_posix.cc
index e765f91390..9fab480a8d 100644
--- a/src/core/lib/support/log_posix.cc
+++ b/src/core/lib/support/log_posix.cc
@@ -56,7 +56,7 @@ void gpr_log(const char* file, int line, gpr_log_severity severity,
   gpr_free(allocated);
 }
 
-extern "C" void gpr_default_log(gpr_log_func_args* args) {
+void gpr_default_log(gpr_log_func_args* args) {
   const char* final_slash;
   const char* display_file;
   char time_buffer[64];
diff --git a/src/core/lib/support/log_windows.cc b/src/core/lib/support/log_windows.cc
index d4481791e2..0013bf448f 100644
--- a/src/core/lib/support/log_windows.cc
+++ b/src/core/lib/support/log_windows.cc
@@ -65,7 +65,7 @@ void gpr_log(const char* file, int line, gpr_log_severity severity,
 }
 
 /* Simple starter implementation */
-extern "C" void gpr_default_log(gpr_log_func_args* args) {
+void gpr_default_log(gpr_log_func_args* args) {
   const char* final_slash;
   const char* display_file;
   char time_buffer[64];
diff --git a/src/core/lib/support/mpscq.h b/src/core/lib/support/mpscq.h
index fb22742050..648ead1f5b 100644
--- a/src/core/lib/support/mpscq.h
+++ b/src/core/lib/support/mpscq.h
@@ -24,10 +24,6 @@
 #include <stdbool.h>
 #include <stddef.h>
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 // Multiple-producer single-consumer lock free queue, based upon the
 // implementation from Dmitry Vyukov here:
 // http://www.1024cores.net/home/lock-free-algorithms/queues/intrusive-mpsc-node-based-queue
@@ -84,8 +80,5 @@ gpr_mpscq_node* gpr_locked_mpscq_try_pop(gpr_locked_mpscq* q);
 // Pop a node.  Returns NULL only if the queue was empty at some point after
 // calling this function
 gpr_mpscq_node* gpr_locked_mpscq_pop(gpr_locked_mpscq* q);
-#ifdef __cplusplus
-}
-#endif
 
 #endif /* GRPC_CORE_LIB_SUPPORT_MPSCQ_H */
diff --git a/src/core/lib/support/murmur_hash.h b/src/core/lib/support/murmur_hash.h
index d02bba6962..422770f103 100644
--- a/src/core/lib/support/murmur_hash.h
+++ b/src/core/lib/support/murmur_hash.h
@@ -23,15 +23,7 @@
 
 #include <stddef.h>
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 /* compute the hash of key (length len) */
 uint32_t gpr_murmur_hash3(const void* key, size_t len, uint32_t seed);
 
-#ifdef __cplusplus
-}
-#endif
-
 #endif /* GRPC_CORE_LIB_SUPPORT_MURMUR_HASH_H */
diff --git a/src/core/lib/support/ref_counted.h b/src/core/lib/support/ref_counted.h
new file mode 100644
index 0000000000..4c662f9119
--- /dev/null
+++ b/src/core/lib/support/ref_counted.h
@@ -0,0 +1,122 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_SUPPORT_REF_COUNTED_H
+#define GRPC_CORE_LIB_SUPPORT_REF_COUNTED_H
+
+#include <grpc/support/log.h>
+#include <grpc/support/sync.h>
+
+#include "src/core/lib/debug/trace.h"
+#include "src/core/lib/support/debug_location.h"
+#include "src/core/lib/support/memory.h"
+
+namespace grpc_core {
+
+// A base class for reference-counted objects.
+// New objects should be created via New() and start with a refcount of 1.
+// When the refcount reaches 0, the object will be deleted via Delete().
+class RefCounted {
+ public:
+  void Ref() { gpr_ref(&refs_); }
+
+  void Unref() {
+    if (gpr_unref(&refs_)) {
+      Delete(this);
+    }
+  }
+
+  // Not copyable nor movable.
+  RefCounted(const RefCounted&) = delete;
+  RefCounted& operator=(const RefCounted&) = delete;
+
+ protected:
+  // Allow Delete() to access destructor.
+  template <typename T>
+  friend void Delete(T*);
+
+  RefCounted() { gpr_ref_init(&refs_, 1); }
+
+  virtual ~RefCounted() {}
+
+ private:
+  gpr_refcount refs_;
+};
+
+// An alternative version of the RefCounted base class that
+// supports tracing.  This is intended to be used in cases where the
+// object will be handled both by idiomatic C++ code using smart
+// pointers and legacy code that is manually calling Ref() and Unref().
+// Once all of our code is converted to idiomatic C++, we may be able to
+// eliminate this class.
+class RefCountedWithTracing {
+ public:
+  void Ref() { gpr_ref(&refs_); }
+
+  void Ref(const DebugLocation& location, const char* reason) {
+    if (location.Log() && trace_flag_ != nullptr && trace_flag_->enabled()) {
+      gpr_atm old_refs = gpr_atm_no_barrier_load(&refs_.count);
+      gpr_log(GPR_DEBUG, "%s:%p %s:%d ref %" PRIdPTR " -> %" PRIdPTR " %s",
+              trace_flag_->name(), this, location.file(), location.line(),
+              old_refs, old_refs + 1, reason);
+    }
+    Ref();
+  }
+
+  void Unref() {
+    if (gpr_unref(&refs_)) {
+      Delete(this);
+    }
+  }
+
+  void Unref(const DebugLocation& location, const char* reason) {
+    if (location.Log() && trace_flag_ != nullptr && trace_flag_->enabled()) {
+      gpr_atm old_refs = gpr_atm_no_barrier_load(&refs_.count);
+      gpr_log(GPR_DEBUG, "%s:%p %s:%d unref %" PRIdPTR " -> %" PRIdPTR " %s",
+              trace_flag_->name(), this, location.file(), location.line(),
+              old_refs, old_refs - 1, reason);
+    }
+    Unref();
+  }
+
+  // Not copyable nor movable.
+  RefCountedWithTracing(const RefCountedWithTracing&) = delete;
+  RefCountedWithTracing& operator=(const RefCountedWithTracing&) = delete;
+
+ protected:
+  // Allow Delete() to access destructor.
+  template <typename T>
+  friend void Delete(T*);
+
+  RefCountedWithTracing() : RefCountedWithTracing(nullptr) {}
+
+  explicit RefCountedWithTracing(TraceFlag* trace_flag)
+      : trace_flag_(trace_flag) {
+    gpr_ref_init(&refs_, 1);
+  }
+
+  virtual ~RefCountedWithTracing() {}
+
+ private:
+  TraceFlag* trace_flag_ = nullptr;
+  gpr_refcount refs_;
+};
+
+}  // namespace grpc_core
+
+#endif /* GRPC_CORE_LIB_SUPPORT_REF_COUNTED_H */
diff --git a/src/core/lib/support/ref_counted_ptr.h b/src/core/lib/support/ref_counted_ptr.h
new file mode 100644
index 0000000000..dc2385e369
--- /dev/null
+++ b/src/core/lib/support/ref_counted_ptr.h
@@ -0,0 +1,90 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_SUPPORT_REF_COUNTED_PTR_H
+#define GRPC_CORE_LIB_SUPPORT_REF_COUNTED_PTR_H
+
+#include <utility>
+
+#include "src/core/lib/support/memory.h"
+
+namespace grpc_core {
+
+// A smart pointer class for objects that provide Ref() and Unref() methods,
+// such as those provided by the RefCounted base class.
+template <typename T>
+class RefCountedPtr {
+ public:
+  RefCountedPtr() {}
+
+  // If value is non-null, we take ownership of a ref to it.
+  explicit RefCountedPtr(T* value) { value_ = value; }
+
+  // Move support.
+  RefCountedPtr(RefCountedPtr&& other) {
+    value_ = other.value_;
+    other.value_ = nullptr;
+  }
+  RefCountedPtr& operator=(RefCountedPtr&& other) {
+    if (value_ != nullptr) value_->Unref();
+    value_ = other.value_;
+    other.value_ = nullptr;
+    return *this;
+  }
+
+  // Copy support.
+  RefCountedPtr(const RefCountedPtr& other) {
+    if (other.value_ != nullptr) other.value_->Ref();
+    value_ = other.value_;
+  }
+  RefCountedPtr& operator=(const RefCountedPtr& other) {
+    // Note: Order of reffing and unreffing is important here in case value_
+    // and other.value_ are the same object.
+    if (other.value_ != nullptr) other.value_->Ref();
+    if (value_ != nullptr) value_->Unref();
+    value_ = other.value_;
+    return *this;
+  }
+
+  ~RefCountedPtr() {
+    if (value_ != nullptr) value_->Unref();
+  }
+
+  // If value is non-null, we take ownership of a ref to it.
+  void reset(T* value = nullptr) {
+    if (value_ != nullptr) value_->Unref();
+    value_ = value;
+  }
+
+  T* get() const { return value_; }
+
+  T& operator*() const { return *value_; }
+  T* operator->() const { return value_; }
+
+ private:
+  T* value_ = nullptr;
+};
+
+template <typename T, typename... Args>
+inline RefCountedPtr<T> MakeRefCounted(Args&&... args) {
+  return RefCountedPtr<T>(New<T>(std::forward<Args>(args)...));
+}
+
+}  // namespace grpc_core
+
+#endif /* GRPC_CORE_LIB_SUPPORT_REF_COUNTED_PTR_H */
diff --git a/src/core/lib/support/string.h b/src/core/lib/support/string.h
index 0b18ffcec1..dd37f0b0e1 100644
--- a/src/core/lib/support/string.h
+++ b/src/core/lib/support/string.h
@@ -24,10 +24,6 @@
 
 #include <grpc/support/port_platform.h>
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 /* String utility functions */
 
 /* Flags for gpr_dump function. */
@@ -109,8 +105,5 @@ void* gpr_memrchr(const void* s, int c, size_t n);
 
 /** Return true if lower(s) equals "true", "yes" or "1", otherwise false. */
 bool gpr_is_true(const char* s);
-#ifdef __cplusplus
-}
-#endif
 
 #endif /* GRPC_CORE_LIB_SUPPORT_STRING_H */
diff --git a/src/core/lib/support/string_windows.h b/src/core/lib/support/string_windows.h
index 6771647581..7c7f31e7aa 100644
--- a/src/core/lib/support/string_windows.h
+++ b/src/core/lib/support/string_windows.h
@@ -21,10 +21,6 @@
 
 #include <grpc/support/port_platform.h>
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 #ifdef GPR_WINDOWS
 
 /* These allocate new strings using gpr_malloc to convert from and to utf-8. */
@@ -33,8 +29,4 @@ LPSTR gpr_tchar_to_char(LPCTSTR input);
 
 #endif /* GPR_WINDOWS */
 
-#ifdef __cplusplus
-}
-#endif
-
 #endif /* GRPC_CORE_LIB_SUPPORT_STRING_WINDOWS_H */
diff --git a/src/core/lib/support/thd_internal.h b/src/core/lib/support/thd_internal.h
new file mode 100644
index 0000000000..38bffc847d
--- /dev/null
+++ b/src/core/lib/support/thd_internal.h
@@ -0,0 +1,30 @@
+/*
+ *
+ * Copyright 2015 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_SUPPORT_THD_INTERNAL_H
+#define GRPC_CORE_LIB_SUPPORT_THD_INTERNAL_H
+
+#include <grpc/support/time.h>
+
+/* Internal interfaces between modules within the gpr support library.  */
+void gpr_thd_init();
+
+/* Wait for all outstanding threads to finish, up to deadline */
+int gpr_await_threads(gpr_timespec deadline);
+
+#endif /* GRPC_CORE_LIB_SUPPORT_THD_INTERNAL_H */
diff --git a/src/core/lib/support/thd_posix.cc b/src/core/lib/support/thd_posix.cc
index fb30880174..339c40fe4c 100644
--- a/src/core/lib/support/thd_posix.cc
+++ b/src/core/lib/support/thd_posix.cc
@@ -24,18 +24,29 @@
 
 #include <grpc/support/alloc.h>
 #include <grpc/support/log.h>
+#include <grpc/support/sync.h>
 #include <grpc/support/thd.h>
 #include <grpc/support/useful.h>
 #include <pthread.h>
 #include <stdlib.h>
 #include <string.h>
 
+#include "src/core/lib/support/fork.h"
+
+static gpr_mu g_mu;
+static gpr_cv g_cv;
+static int g_thread_count;
+static int g_awaiting_threads;
+
 struct thd_arg {
   void (*body)(void* arg); /* body of a thread */
   void* arg;               /* argument to a thread */
   const char* name;        /* name of thread. Can be nullptr. */
 };
 
+static void inc_thd_count();
+static void dec_thd_count();
+
 /* Body of every thread started via gpr_thd_new. */
 static void* thread_body(void* v) {
   struct thd_arg a = *(struct thd_arg*)v;
@@ -54,6 +65,7 @@ static void* thread_body(void* v) {
 #endif // GPR_APPLE_PTHREAD_NAME
   }
   (*a.body)(a.arg);
+  dec_thd_count();
   return nullptr;
 }
 
@@ -70,6 +82,7 @@ int gpr_thd_new(gpr_thd_id* t, const char* thd_name,
   a->body = thd_body;
   a->arg = arg;
   a->name = thd_name;
+  inc_thd_count();
 
   GPR_ASSERT(pthread_attr_init(&attr) == 0);
   if (gpr_thd_options_is_detached(options)) {
@@ -84,6 +97,7 @@ int gpr_thd_new(gpr_thd_id* t, const char* thd_name,
   if (!thread_started) {
     /* don't use gpr_free, as this was allocated using malloc (see above) */
     free(a);
+    dec_thd_count();
   }
   *t = (gpr_thd_id)p;
   return thread_started;
@@ -93,4 +107,46 @@ gpr_thd_id gpr_thd_currentid(void) { return (gpr_thd_id)pthread_self(); }
 
 void gpr_thd_join(gpr_thd_id t) { pthread_join((pthread_t)t, nullptr); }
 
+/*****************************************
+ * Only used when fork support is enabled
+ */
+
+static void inc_thd_count() {
+  if (grpc_fork_support_enabled()) {
+    gpr_mu_lock(&g_mu);
+    g_thread_count++;
+    gpr_mu_unlock(&g_mu);
+  }
+}
+
+static void dec_thd_count() {
+  if (grpc_fork_support_enabled()) {
+    gpr_mu_lock(&g_mu);
+    g_thread_count--;
+    if (g_awaiting_threads && g_thread_count == 0) {
+      gpr_cv_signal(&g_cv);
+    }
+    gpr_mu_unlock(&g_mu);
+  }
+}
+
+void gpr_thd_init() {
+  gpr_mu_init(&g_mu);
+  gpr_cv_init(&g_cv);
+  g_thread_count = 0;
+  g_awaiting_threads = 0;
+}
+
+int gpr_await_threads(gpr_timespec deadline) {
+  gpr_mu_lock(&g_mu);
+  g_awaiting_threads = 1;
+  int res = 0;
+  if (g_thread_count > 0) {
+    res = gpr_cv_wait(&g_cv, &g_mu, deadline);
+  }
+  g_awaiting_threads = 0;
+  gpr_mu_unlock(&g_mu);
+  return res == 0;
+}
+
 #endif /* GPR_POSIX_SYNC */
diff --git a/src/core/lib/support/thd_windows.cc b/src/core/lib/support/thd_windows.cc
index b54d0b6c62..f920770f32 100644
--- a/src/core/lib/support/thd_windows.cc
+++ b/src/core/lib/support/thd_windows.cc
@@ -50,6 +50,8 @@ static void destroy_thread(struct thd_info* t) {
   gpr_free(t);
 }
 
+void gpr_thd_init(void) {}
+
 /* Body of every thread started via gpr_thd_new. */
 static DWORD WINAPI thread_body(void* v) {
   g_thd_info = (struct thd_info*)v;
diff --git a/src/core/lib/support/time_posix.cc b/src/core/lib/support/time_posix.cc
index 7f65205800..47a849480f 100644
--- a/src/core/lib/support/time_posix.cc
+++ b/src/core/lib/support/time_posix.cc
@@ -127,9 +127,7 @@ static gpr_timespec now_impl(gpr_clock_type clock) {
 }
 #endif
 
-extern "C" {
 gpr_timespec (*gpr_now_impl)(gpr_clock_type clock_type) = now_impl;
-}
 
 #ifdef GPR_LOW_LEVEL_COUNTERS
 gpr_atm gpr_now_call_count;
diff --git a/src/core/lib/support/time_precise.h b/src/core/lib/support/time_precise.h
index 3befda3d86..35cd154dbd 100644
--- a/src/core/lib/support/time_precise.h
+++ b/src/core/lib/support/time_precise.h
@@ -21,15 +21,7 @@
 
 #include <grpc/support/time.h>
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 void gpr_precise_clock_init(void);
 void gpr_precise_clock_now(gpr_timespec* clk);
 
-#ifdef __cplusplus
-}
-#endif
-
 #endif /* GRPC_CORE_LIB_SUPPORT_TIME_PRECISE_H */
diff --git a/src/core/lib/support/time_windows.cc b/src/core/lib/support/time_windows.cc
index 08c1b22964..fb17e5c079 100644
--- a/src/core/lib/support/time_windows.cc
+++ b/src/core/lib/support/time_windows.cc
@@ -68,9 +68,7 @@ static gpr_timespec now_impl(gpr_clock_type clock) {
   return now_tv;
 }
 
-extern "C" {
 gpr_timespec (*gpr_now_impl)(gpr_clock_type clock_type) = now_impl;
-}
 
 gpr_timespec gpr_now(gpr_clock_type clock_type) {
   return gpr_now_impl(clock_type);
diff --git a/src/core/lib/support/tmpfile.h b/src/core/lib/support/tmpfile.h
index 437d871786..c5ceda8675 100644
--- a/src/core/lib/support/tmpfile.h
+++ b/src/core/lib/support/tmpfile.h
@@ -21,18 +21,10 @@
 
 #include <stdio.h>
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 /* Creates a temporary file from a prefix.
    If tmp_filename is not NULL, *tmp_filename is assigned the name of the
    created file and it is the responsibility of the caller to gpr_free it
    unless an error occurs in which case it will be set to NULL. */
 FILE* gpr_tmpfile(const char* prefix, char** tmp_filename);
 
-#ifdef __cplusplus
-}
-#endif
-
 #endif /* GRPC_CORE_LIB_SUPPORT_TMPFILE_H */