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src/core/ext/transport/chttp2/transport/chttp2_plugin.cc

@@ -18,8 +18,16 @@
 
 #include "src/core/ext/transport/chttp2/transport/chttp2_transport.h"
 #include "src/core/lib/debug/trace.h"
+#include "src/core/lib/support/env.h"
 #include "src/core/lib/transport/metadata.h"
 
-void grpc_chttp2_plugin_init(void) {}
+void grpc_chttp2_plugin_init(void) {
+  g_flow_control_enabled = true;
+  char* env_variable = gpr_getenv("GRPC_EXPERIMENTAL_DISABLE_FLOW_CONTROL");
+  if (env_variable != nullptr) {
+    g_flow_control_enabled = false;
+    gpr_free(env_variable);
+  }
+}
 
 void grpc_chttp2_plugin_shutdown(void) {}

src/core/ext/transport/chttp2/transport/chttp2_transport.cc

@@ -152,6 +152,10 @@ static void keepalive_watchdog_fired_locked(void* arg, grpc_error* error);
 
 static void reset_byte_stream(void* arg, grpc_error* error);
 
+// Flow control default enabled. Can be disabled by setting
+// GRPC_EXPERIMENTAL_DISABLE_FLOW_CONTROL
+bool g_flow_control_enabled = true;
+
 /*******************************************************************************
  * CONSTRUCTION/DESTRUCTION/REFCOUNTING
  */
@@ -232,9 +236,6 @@ void grpc_chttp2_ref_transport(grpc_chttp2_transport* t) { gpr_ref(&t->refs); }
 
 static const grpc_transport_vtable* get_vtable(void);
 
-// -1 == unset, 0 == disabled, 1 == enabled
-static gpr_atm flow_control_enabled = -1;
-
 static void init_transport(grpc_chttp2_transport* t,
                            const grpc_channel_args* channel_args,
                            grpc_endpoint* ep, bool is_client) {
@@ -520,17 +521,7 @@ static void init_transport(grpc_chttp2_transport* t,
     }
   }
 
-  if (gpr_atm_no_barrier_load(&flow_control_enabled) == -1) {
-    char* env_variable = gpr_getenv("GRPC_EXPERIMENTAL_DISABLE_FLOW_CONTROL");
-    if (env_variable != nullptr) {
-      gpr_atm_no_barrier_store(&flow_control_enabled, 0);
-    } else {
-      gpr_atm_no_barrier_store(&flow_control_enabled, 1);
-    }
-    gpr_free(env_variable);
-  }
-
-  if (gpr_atm_no_barrier_load(&flow_control_enabled)) {
+  if (g_flow_control_enabled) {
     t->flow_control.Init<grpc_core::chttp2::TransportFlowControl>(t,
                                                                   enable_bdp);
   } else {

src/core/ext/transport/chttp2/transport/chttp2_transport.h

@@ -27,6 +27,8 @@ extern grpc_core::TraceFlag grpc_http_trace;
 extern grpc_core::TraceFlag grpc_trace_http2_stream_state;
 extern grpc_core::DebugOnlyTraceFlag grpc_trace_chttp2_refcount;
 
+extern bool g_flow_control_enabled;
+
 grpc_transport* grpc_create_chttp2_transport(
     const grpc_channel_args* channel_args, grpc_endpoint* ep, bool is_client);