From 67a4eb6623d0870992051d0280b78dd7a2b2c0ff Mon Sep 17 00:00:00 2001
From: Muxi Yan <mxyan@google.com>
Date: Thu, 18 Oct 2018 09:53:41 -0700
Subject: [PATCH] Lock GRPCCall in GRPCAuthorizatioProtocol

---
 src/objective-c/GRPCClient/GRPCCall.m | 26 ++++++++++++++++----------
 1 file changed, 16 insertions(+), 10 deletions(-)

diff --git a/src/objective-c/GRPCClient/GRPCCall.m b/src/objective-c/GRPCClient/GRPCCall.m
index 5ffdfbaa89f..68f0f8892d7 100644
--- a/src/objective-c/GRPCClient/GRPCCall.m
+++ b/src/objective-c/GRPCClient/GRPCCall.m
@@ -461,10 +461,12 @@ const char *kCFStreamVarName = "grpc_cfstream";
 }
 
 - (void)cancel {
-  if (!self.isWaitingForToken) {
-    [self cancelCall];
-  } else {
-    self.isWaitingForToken = NO;
+  @synchronized (self) {
+    if (!self.isWaitingForToken) {
+      [self cancelCall];
+    } else {
+      self.isWaitingForToken = NO;
+    }
   }
   [self
       maybeFinishWithError:[NSError
@@ -779,14 +781,18 @@ const char *kCFStreamVarName = "grpc_cfstream";
     _callOptions = callOptions;
   }
   if (_callOptions.authTokenProvider != nil) {
-    self.isWaitingForToken = YES;
+    @synchronized (self) {
+      self.isWaitingForToken = YES;
+    }
     [self.tokenProvider getTokenWithHandler:^(NSString *token) {
-      if (self.isWaitingForToken) {
-        if (token) {
-          self->_fetchedOauth2AccessToken = [token copy];
+      @synchronized (self) {
+        if (self.isWaitingForToken) {
+          if (token) {
+            self->_fetchedOauth2AccessToken = [token copy];
+          }
+          [self startCallWithWriteable:writeable];
+          self.isWaitingForToken = NO;
         }
-        [self startCallWithWriteable:writeable];
-        self.isWaitingForToken = NO;
       }
     }];
   } else {