Merge pull request #2379 from ctiller/nanana-im-batman

Fix TSAN reported race

1 files changed, 16 insertions, 2 deletions

diff --git a/src/core/transport/metadata.c b/src/core/transport/metadata.c
index 9cbb0952d0..71fcb2fc14 100644
--- a/src/core/transport/metadata.c
+++ b/src/core/transport/metadata.c
@@ -87,6 +87,7 @@ typedef struct internal_metadata {
   gpr_atm refcnt;
 
   /* private only data */
+  gpr_mu mu_user_data;
   void *user_data;
   void (*destroy_user_data)(void *user_data);
 
@@ -200,6 +201,7 @@ static void discard_metadata(grpc_mdctx *ctx) {
       if (cur->user_data) {
         cur->destroy_user_data(cur->user_data);
       }
+      gpr_mu_destroy(&cur->mu_user_data);
       gpr_free(cur);
       cur = next;
       ctx->mdtab_free--;
@@ -467,6 +469,7 @@ grpc_mdelem *grpc_mdelem_from_metadata_strings(grpc_mdctx *ctx,
   md->user_data = NULL;
   md->destroy_user_data = NULL;
   md->bucket_next = ctx->mdtab[hash % ctx->mdtab_capacity];
+  gpr_mu_init(&md->mu_user_data);
 #ifdef GRPC_METADATA_REFCOUNT_DEBUG
   gpr_log(GPR_DEBUG, "ELM   NEW:%p:%d: '%s' = '%s'", md,
           gpr_atm_no_barrier_load(&md->refcnt),
@@ -581,18 +584,29 @@ size_t grpc_mdctx_get_mdtab_free_test_only(grpc_mdctx *ctx) {
 void *grpc_mdelem_get_user_data(grpc_mdelem *md,
                                 void (*if_destroy_func)(void *)) {
   internal_metadata *im = (internal_metadata *)md;
-  return im->destroy_user_data == if_destroy_func ? im->user_data : NULL;
+  void *result;
+  gpr_mu_lock(&im->mu_user_data);
+  result = im->destroy_user_data == if_destroy_func ? im->user_data : NULL;
+  gpr_mu_unlock(&im->mu_user_data);
+  return result;
 }
 
 void grpc_mdelem_set_user_data(grpc_mdelem *md, void (*destroy_func)(void *),
                                void *user_data) {
   internal_metadata *im = (internal_metadata *)md;
   GPR_ASSERT((user_data == NULL) == (destroy_func == NULL));
+  gpr_mu_lock(&im->mu_user_data);
   if (im->destroy_user_data) {
-    im->destroy_user_data(im->user_data);
+    /* user data can only be set once */
+    gpr_mu_unlock(&im->mu_user_data);
+    if (destroy_func != NULL) {
+      destroy_func(user_data);
+    }
+    return;
   }
   im->destroy_user_data = destroy_func;
   im->user_data = user_data;
+  gpr_mu_unlock(&im->mu_user_data);
 }
 
 gpr_slice grpc_mdstr_as_base64_encoded_and_huffman_compressed(grpc_mdstr *gs) {