Index: test/asan/TestCases/Linux/recvfrom.cc
===================================================================
--- test/asan/TestCases/Linux/recvfrom.cc
+++ test/asan/TestCases/Linux/recvfrom.cc
@@ -2,7 +2,6 @@
 //
 // RUN: %clangxx_asan %s -o %t && not %run %t 2>&1 | FileCheck %s
 //
-// REQUIRES: broken
 // UNSUPPORTED: android
 
 #include <stdio.h>
@@ -14,26 +13,38 @@
 #include <sys/socket.h>
 #include <pthread.h>
 
-const int kPortNum = 1234;
+#define CHECK_ERROR(p, m)   \
+  if (p) {                  \
+    fprintf(stderr, m);     \
+    exit(1);                \
+  }
+
 const int kBufSize = 10;
+pthread_mutex_t server_ready_mu = PTHREAD_MUTEX_INITIALIZER;
 
 static void *server_thread_udp(void *data) {
   char buf[kBufSize / 2];
-  struct sockaddr_in serveraddr; // server's addr
+  struct sockaddr_in serveraddr;
+  socklen_t addrlen;
   int sockfd = socket(AF_INET, SOCK_DGRAM, 0);
-  if (sockfd < 0)
-    fprintf(stderr, "ERROR opening socket\n");
+  CHECK_ERROR(sockfd < 0, "ERROR opening socket.\n");
 
-  memset((char *) &serveraddr, 0, sizeof(serveraddr));
+  memset((char *)&serveraddr, 0, sizeof(serveraddr));
   serveraddr.sin_family = AF_INET;
   serveraddr.sin_addr.s_addr = htonl(INADDR_ANY);
-  serveraddr.sin_port = htons(kPortNum);
+  serveraddr.sin_port = htons(0);
+
+  int bound = bind(sockfd, (struct sockaddr *)&serveraddr, sizeof(serveraddr));
+  CHECK_ERROR(bound < 0, "ERROR on binding.\n");
 
-  if (bind(sockfd, (struct sockaddr *) &serveraddr, sizeof(serveraddr)) < 0)
-    fprintf(stderr, "ERROR on binding\n");
+  // Provide necessary information (e.g. port number) to client thread.
+  int succeeded = getsockname(sockfd, (struct sockaddr *)data, &addrlen);
+  CHECK_ERROR(succeeded < 0, "ERROR in getsockname.\n");
 
+  // Now it's safe to unblock client thread.
+  pthread_mutex_unlock(&server_ready_mu);
   recvfrom(sockfd, buf, kBufSize, 0, NULL, NULL); // BOOM
-  // CHECK: {{WRITE of size 9 at 0x.* thread T1}}
+  // CHECK: {{WRITE of size 10 at 0x.* thread T1}}
   // CHECK: {{    #1 0x.* in server_thread_udp.*recvfrom.cc:}}[[@LINE-2]]
   // CHECK: {{Address 0x.* is located in stack of thread T1 at offset}}
   // CHECK-NEXT: in{{.*}}server_thread_udp{{.*}}recvfrom.cc
@@ -41,39 +52,29 @@
 }
 
 int main() {
-  char buf[kBufSize] = "123456789";
-  struct sockaddr_in serveraddr; // server's addr
-
+  char buf[kBufSize];
+  struct sockaddr_in serveraddr;
   pthread_t server_thread;
-  if (pthread_create(&server_thread, NULL, server_thread_udp, NULL)) {
-    fprintf(stderr, "Error creating thread\n");
-    exit(1);
-  }
 
-  int sockfd = socket(AF_INET, SOCK_DGRAM, 0);
-  struct hostent *server;
-  char hostname[] = "localhost";
-  if (sockfd < 0)
-    fprintf(stderr, "ERROR opening socket\n");
+  memset((char *)&serveraddr, 0, sizeof(serveraddr));
+  // Default state for server_ready_mu is 'unlocked'. Lock it to make sure
+  // following pthread_mutex_lock won't pass before server becomes ready.
+  pthread_mutex_lock(&server_ready_mu);
+  int succeeded = pthread_create(&server_thread, NULL, server_thread_udp,
+                                 (void *)&serveraddr);
+  CHECK_ERROR(succeeded, "Error creating thread.\n");
 
-  server = gethostbyname(hostname);
-  if (!server) {
-    fprintf(stderr,"ERROR, no such host as %s\n", hostname);
-    exit(1);
-  }
+  int sockfd = socket(AF_INET, SOCK_DGRAM, 0);
+  CHECK_ERROR(sockfd < 0, "ERROR opening socket.\n");
 
-  memset((char *) &serveraddr, 0, sizeof(serveraddr));
-  serveraddr.sin_family = AF_INET;
-  memcpy((char *)&serveraddr.sin_addr.s_addr, (char *)server->h_addr,
-          server->h_length);
-  serveraddr.sin_port = htons(kPortNum);
-  sendto(sockfd, buf, strlen(buf), 0, (struct sockaddr *) &serveraddr,
+  // Wait for server that should properly initialize serveraddr.
+  pthread_mutex_lock(&server_ready_mu);
+  sendto(sockfd, buf, sizeof(buf), 0, (struct sockaddr *)&serveraddr,
          sizeof(serveraddr));
 
-  if (pthread_join(server_thread, NULL)) {
-    fprintf(stderr, "Error joining thread\n");
-    exit(1);
-  }
-
+  succeeded = pthread_join(server_thread, NULL);
+  CHECK_ERROR(succeeded, "Error joining thread.\n");
+  pthread_mutex_unlock(&server_ready_mu);
+  pthread_mutex_destroy(&server_ready_mu);
   return 0;
 }