Removing instances of exec_ctx being passed around in functions in

src/core. exec_ctx is now a thread_local pointer of type ExecCtx instead of
grpc_exec_ctx which is initialized whenever ExecCtx is instantiated. ExecCtx
also keeps track of the previous exec_ctx so that nesting of exec_ctx is
allowed. This means that there is only one exec_ctx being used at any
time. Also, grpc_exec_ctx_finish is called in the destructor of the
object, and the previous exec_ctx is restored to avoid breaking current
functionality. The code still explicitly calls grpc_exec_ctx_finish
because removing all such instances causes the code to break.

2 files changed, 177 insertions, 30 deletions

diff --git a/test/core/backoff/backoff_test.c b/test/core/backoff/backoff_test.c
index a29cce6cc7..93952f3d10 100644
--- a/test/core/backoff/backoff_test.c
+++ b/test/core/backoff/backoff_test.c
@@ -28,15 +28,15 @@ static void test_constant_backoff(void) {
                     0.0 /* jitter */, 100 /* min timeout */,
                     1000 /* max timeout */);
 
-  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-  grpc_millis next = grpc_backoff_begin(&exec_ctx, &backoff);
-  GPR_ASSERT(next - grpc_exec_ctx_now(&exec_ctx) == 200);
+  exec_ctx = GRPC_EXEC_CTX_INIT;
+  grpc_millis next = grpc_backoff_begin(&backoff);
+  GPR_ASSERT(next - grpc_exec_ctx_now() == 200);
   for (int i = 0; i < 10000; i++) {
-    next = grpc_backoff_step(&exec_ctx, &backoff);
-    GPR_ASSERT(next - grpc_exec_ctx_now(&exec_ctx) == 200);
+    next = grpc_backoff_step(&backoff);
+    GPR_ASSERT(next - grpc_exec_ctx_now() == 200);
     exec_ctx.now = next;
   }
-  grpc_exec_ctx_finish(&exec_ctx);
+  grpc_exec_ctx_finish();
 }
 
 static void test_min_connect(void) {
@@ -45,10 +45,10 @@ static void test_min_connect(void) {
                     0.0 /* jitter */, 200 /* min timeout */,
                     1000 /* max timeout */);
 
-  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-  grpc_millis next = grpc_backoff_begin(&exec_ctx, &backoff);
-  GPR_ASSERT(next - grpc_exec_ctx_now(&exec_ctx) == 200);
-  grpc_exec_ctx_finish(&exec_ctx);
+  exec_ctx = GRPC_EXEC_CTX_INIT;
+  grpc_millis next = grpc_backoff_begin(&backoff);
+  GPR_ASSERT(next - grpc_exec_ctx_now() == 200);
+  grpc_exec_ctx_finish();
 }
 
 static void test_no_jitter_backoff(void) {
@@ -58,47 +58,47 @@ static void test_no_jitter_backoff(void) {
                     513 /* max timeout */);
   // x_1 = 2
   // x_n = 2**i + x_{i-1} ( = 2**(n+1) - 2 )
-  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
+  exec_ctx = GRPC_EXEC_CTX_INIT;
   exec_ctx.now = 0;
   exec_ctx.now_is_valid = true;
-  grpc_millis next = grpc_backoff_begin(&exec_ctx, &backoff);
+  grpc_millis next = grpc_backoff_begin(&backoff);
   GPR_ASSERT(next == 2);
   exec_ctx.now = next;
-  next = grpc_backoff_step(&exec_ctx, &backoff);
+  next = grpc_backoff_step(&backoff);
   GPR_ASSERT(next == 6);
   exec_ctx.now = next;
-  next = grpc_backoff_step(&exec_ctx, &backoff);
+  next = grpc_backoff_step(&backoff);
   GPR_ASSERT(next == 14);
   exec_ctx.now = next;
-  next = grpc_backoff_step(&exec_ctx, &backoff);
+  next = grpc_backoff_step(&backoff);
   GPR_ASSERT(next == 30);
   exec_ctx.now = next;
-  next = grpc_backoff_step(&exec_ctx, &backoff);
+  next = grpc_backoff_step(&backoff);
   GPR_ASSERT(next == 62);
   exec_ctx.now = next;
-  next = grpc_backoff_step(&exec_ctx, &backoff);
+  next = grpc_backoff_step(&backoff);
   GPR_ASSERT(next == 126);
   exec_ctx.now = next;
-  next = grpc_backoff_step(&exec_ctx, &backoff);
+  next = grpc_backoff_step(&backoff);
   GPR_ASSERT(next == 254);
   exec_ctx.now = next;
-  next = grpc_backoff_step(&exec_ctx, &backoff);
+  next = grpc_backoff_step(&backoff);
   GPR_ASSERT(next == 510);
   exec_ctx.now = next;
-  next = grpc_backoff_step(&exec_ctx, &backoff);
+  next = grpc_backoff_step(&backoff);
   GPR_ASSERT(next == 1022);
   exec_ctx.now = next;
-  next = grpc_backoff_step(&exec_ctx, &backoff);
+  next = grpc_backoff_step(&backoff);
   // Hit the maximum timeout. From this point onwards, retries will increase
   // only by max timeout.
   GPR_ASSERT(next == 1535);
   exec_ctx.now = next;
-  next = grpc_backoff_step(&exec_ctx, &backoff);
+  next = grpc_backoff_step(&backoff);
   GPR_ASSERT(next == 2048);
   exec_ctx.now = next;
-  next = grpc_backoff_step(&exec_ctx, &backoff);
+  next = grpc_backoff_step(&backoff);
   GPR_ASSERT(next == 2561);
-  grpc_exec_ctx_finish(&exec_ctx);
+  grpc_exec_ctx_finish();
 }
 
 static void test_jitter_backoff(void) {
@@ -111,9 +111,9 @@ static void test_jitter_backoff(void) {
 
   backoff.rng_state = 0;  // force consistent PRNG
 
-  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-  grpc_millis next = grpc_backoff_begin(&exec_ctx, &backoff);
-  GPR_ASSERT(next - grpc_exec_ctx_now(&exec_ctx) == 500);
+  exec_ctx = GRPC_EXEC_CTX_INIT;
+  grpc_millis next = grpc_backoff_begin(&backoff);
+  GPR_ASSERT(next - grpc_exec_ctx_now() == 500);
 
   int64_t expected_next_lower_bound =
       (int64_t)((double)initial_timeout * (1 - jitter));
@@ -121,10 +121,10 @@ static void test_jitter_backoff(void) {
       (int64_t)((double)initial_timeout * (1 + jitter));
 
   for (int i = 0; i < 10000; i++) {
-    next = grpc_backoff_step(&exec_ctx, &backoff);
+    next = grpc_backoff_step(&backoff);
 
     // next-now must be within (jitter*100)% of the previous timeout.
-    const int64_t timeout_millis = next - grpc_exec_ctx_now(&exec_ctx);
+    const int64_t timeout_millis = next - grpc_exec_ctx_now();
     GPR_ASSERT(timeout_millis >= expected_next_lower_bound);
     GPR_ASSERT(timeout_millis <= expected_next_upper_bound);
 
@@ -134,7 +134,7 @@ static void test_jitter_backoff(void) {
         (int64_t)((double)timeout_millis * (1 + jitter));
     exec_ctx.now = next;
   }
-  grpc_exec_ctx_finish(&exec_ctx);
+  grpc_exec_ctx_finish();
 }
 
 int main(int argc, char **argv) {
diff --git a/test/core/backoff/backoff_test.cc b/test/core/backoff/backoff_test.cc
new file mode 100644
index 0000000000..ea27f7547f
--- /dev/null
+++ b/test/core/backoff/backoff_test.cc
@@ -0,0 +1,147 @@
+/*
+ *
+ * Copyright 2016 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/backoff/backoff.h"
+
+#include <grpc/support/log.h>
+
+#include "test/core/util/test_config.h"
+
+static void test_constant_backoff(void) {
+  grpc_backoff backoff;
+  grpc_backoff_init(&backoff, 200 /* initial timeout */, 1.0 /* multiplier */,
+                    0.0 /* jitter */, 100 /* min timeout */,
+                    1000 /* max timeout */);
+
+  grpc_millis next = grpc_backoff_begin(&backoff);
+  GPR_ASSERT(next - grpc_exec_ctx_now() == 200);
+  for (int i = 0; i < 10000; i++) {
+    next = grpc_backoff_step(&backoff);
+    GPR_ASSERT(next - grpc_exec_ctx_now() == 200);
+    exec_ctx.now = next;
+  }
+  grpc_exec_ctx_finish();
+}
+
+static void test_min_connect(void) {
+  grpc_backoff backoff;
+  grpc_backoff_init(&backoff, 100 /* initial timeout */, 1.0 /* multiplier */,
+                    0.0 /* jitter */, 200 /* min timeout */,
+                    1000 /* max timeout */);
+
+  grpc_millis next = grpc_backoff_begin(&backoff);
+  GPR_ASSERT(next - grpc_exec_ctx_now() == 200);
+  grpc_exec_ctx_finish();
+}
+
+static void test_no_jitter_backoff(void) {
+  grpc_backoff backoff;
+  grpc_backoff_init(&backoff, 2 /* initial timeout */, 2.0 /* multiplier */,
+                    0.0 /* jitter */, 1 /* min timeout */,
+                    513 /* max timeout */);
+  // x_1 = 2
+  // x_n = 2**i + x_{i-1} ( = 2**(n+1) - 2 )
+
+  exec_ctx.now = 0;
+  exec_ctx.now_is_valid = true;
+  grpc_millis next = grpc_backoff_begin(&backoff);
+  GPR_ASSERT(next == 2);
+  exec_ctx.now = next;
+  next = grpc_backoff_step(&backoff);
+  GPR_ASSERT(next == 6);
+  exec_ctx.now = next;
+  next = grpc_backoff_step(&backoff);
+  GPR_ASSERT(next == 14);
+  exec_ctx.now = next;
+  next = grpc_backoff_step(&backoff);
+  GPR_ASSERT(next == 30);
+  exec_ctx.now = next;
+  next = grpc_backoff_step(&backoff);
+  GPR_ASSERT(next == 62);
+  exec_ctx.now = next;
+  next = grpc_backoff_step(&backoff);
+  GPR_ASSERT(next == 126);
+  exec_ctx.now = next;
+  next = grpc_backoff_step(&backoff);
+  GPR_ASSERT(next == 254);
+  exec_ctx.now = next;
+  next = grpc_backoff_step(&backoff);
+  GPR_ASSERT(next == 510);
+  exec_ctx.now = next;
+  next = grpc_backoff_step(&backoff);
+  GPR_ASSERT(next == 1022);
+  exec_ctx.now = next;
+  next = grpc_backoff_step(&backoff);
+  // Hit the maximum timeout. From this point onwards, retries will increase
+  // only by max timeout.
+  GPR_ASSERT(next == 1535);
+  exec_ctx.now = next;
+  next = grpc_backoff_step(&backoff);
+  GPR_ASSERT(next == 2048);
+  exec_ctx.now = next;
+  next = grpc_backoff_step(&backoff);
+  GPR_ASSERT(next == 2561);
+  grpc_exec_ctx_finish();
+}
+
+static void test_jitter_backoff(void) {
+  const int64_t initial_timeout = 500;
+  const double jitter = 0.1;
+  grpc_backoff backoff;
+  grpc_backoff_init(&backoff, (grpc_millis)initial_timeout,
+                    1.0 /* multiplier */, jitter, 100 /* min timeout */,
+                    1000 /* max timeout */);
+
+  backoff.rng_state = 0;  // force consistent PRNG
+
+  grpc_millis next = grpc_backoff_begin(&backoff);
+  GPR_ASSERT(next - grpc_exec_ctx_now() == 500);
+
+  int64_t expected_next_lower_bound =
+      (int64_t)((double)initial_timeout * (1 - jitter));
+  int64_t expected_next_upper_bound =
+      (int64_t)((double)initial_timeout * (1 + jitter));
+
+  for (int i = 0; i < 10000; i++) {
+    next = grpc_backoff_step(&backoff);
+
+    // next-now must be within (jitter*100)% of the previous timeout.
+    const int64_t timeout_millis = next - grpc_exec_ctx_now();
+    GPR_ASSERT(timeout_millis >= expected_next_lower_bound);
+    GPR_ASSERT(timeout_millis <= expected_next_upper_bound);
+
+    expected_next_lower_bound =
+        (int64_t)((double)timeout_millis * (1 - jitter));
+    expected_next_upper_bound =
+        (int64_t)((double)timeout_millis * (1 + jitter));
+    exec_ctx.now = next;
+  }
+  grpc_exec_ctx_finish();
+}
+
+int main(int argc, char **argv) {
+  grpc_test_init(argc, argv);
+  gpr_time_init();
+
+  test_constant_backoff();
+  test_min_connect();
+  test_no_jitter_backoff();
+  test_jitter_backoff();
+
+  return 0;
+}