Fix real TSAN/ASAN bug

src/core/lib/channel/channel_stack.h

@@ -84,7 +84,7 @@ typedef struct {
 typedef struct {
   grpc_call_stats stats;
   grpc_status_code final_status;
-  const char* error_string;
+  const char** error_string;
 } grpc_call_final_info;
 
 /* Channel filters specify:

src/core/lib/iomgr/error.cc

@@ -754,7 +754,7 @@ const char* grpc_error_string(grpc_error* err) {
 
   if (!gpr_atm_rel_cas(&err->atomics.error_string, 0, (gpr_atm)out)) {
     gpr_free(out);
-    out = (char*)gpr_atm_acq_load(&err->atomics.error_string);
+    out = (char*)gpr_atm_no_barrier_load(&err->atomics.error_string);
   }
 
   GPR_TIMER_END("grpc_error_string", 0);

src/core/lib/surface/call.cc

@@ -551,7 +551,7 @@ static void destroy_call(grpc_exec_ctx* exec_ctx, void* call,
 
   get_final_status(exec_ctx, c, set_status_value_directly,
                    &c->final_info.final_status, nullptr,
-                   &c->final_info.error_string);
+                   c->final_info.error_string);
   c->final_info.stats.latency =
       gpr_time_sub(gpr_now(GPR_CLOCK_MONOTONIC), c->start_time);