Fix IO thread hang on releasing a socket.

net/socket/client_socket_pool_base_unittest.cc

Index: net/socket/client_socket_pool_base_unittest.cc
diff --git a/net/socket/client_socket_pool_base_unittest.cc b/net/socket/client_socket_pool_base_unittest.cc
index 3e20eb9b87286815f7ba504b738aa14fb7c6203c..7e26ec6670f923246044820adb9baffa9e7246f9 100644
--- a/net/socket/client_socket_pool_base_unittest.cc
+++ b/net/socket/client_socket_pool_base_unittest.cc
@@ -1455,6 +1455,70 @@ TEST_F(ClientSocketPoolBaseTest, MultipleReleasingDisconnectedSockets) {
   EXPECT_FALSE(req4.handle()->is_reused());
 }
 
+// Regression test for http://crbug.com/42267.
+// When DoReleaseSocket() is processed for one socket, it is blocked because the
+// other stalled groups all have releasing sockets, so no progress can be made.
+TEST_F(ClientSocketPoolBaseTest, SocketLimitReleasingSockets) {
+  CreatePoolWithIdleTimeouts(
+      4 /* socket limit */, 4 /* socket limit per group */,
+      base::TimeDelta(),  // Time out unused sockets immediately.
+      base::TimeDelta::FromDays(1));  // Don't time out used sockets.
+
+  connect_job_factory_->set_job_type(TestConnectJob::kMockJob);
+
+  // Max out the socket limit with 2 per group.
+
+  scoped_ptr<TestSocketRequest> req_a[4];
+  scoped_ptr<TestSocketRequest> req_b[4];
+
+  for (int i = 0; i < 2; ++i) {
+    req_a[i].reset(new TestSocketRequest(&request_order_, &completion_count_));
+    req_b[i].reset(new TestSocketRequest(&request_order_, &completion_count_));
+    EXPECT_EQ(OK,
+              InitHandle(req_a[i]->handle(), "a", LOWEST, req_a[i].get(), pool_,
+                         BoundNetLog()));
+    EXPECT_EQ(OK,
+              InitHandle(req_b[i]->handle(), "b", LOWEST, req_b[i].get(), pool_,
+                         BoundNetLog()));
+  }
+  
+  // Make 4 pending requests, 2 per group.
+
+  for (int i = 2; i < 4; ++i) {
+    req_a[i].reset(new TestSocketRequest(&request_order_, &completion_count_));
+    req_b[i].reset(new TestSocketRequest(&request_order_, &completion_count_));
+    EXPECT_EQ(ERR_IO_PENDING,
+              InitHandle(req_a[i]->handle(), "a", LOWEST, req_a[i].get(), pool_,
+                         BoundNetLog()));
+    EXPECT_EQ(ERR_IO_PENDING,
+              InitHandle(req_b[i]->handle(), "b", LOWEST, req_b[i].get(), pool_,
+                         BoundNetLog()));
+  }
+
+  // Release b's socket first.  The order is important, because in
+  // DoReleaseSocket(), we'll process b's released socket, and since both b and
+  // a are stalled, but 'a' is lower lexicographically, we'll process group 'a'
+  // first, which has a releasing socket, so it refuses to start up another
+  // ConnectJob.  So, we used to infinite loop on this.
+  req_b[0]->handle()->socket()->Disconnect();
+  req_b[0]->handle()->Reset();
+  req_a[0]->handle()->socket()->Disconnect();
+  req_a[0]->handle()->Reset();
+
+  // Used to get stuck here.
+  MessageLoop::current()->RunAllPending();
+
+  req_b[1]->handle()->socket()->Disconnect();
+  req_b[1]->handle()->Reset();
+  req_a[1]->handle()->socket()->Disconnect();
+  req_a[1]->handle()->Reset();
+
+  for (int i = 2; i < 4; ++i) {
+    EXPECT_EQ(OK, req_b[i]->WaitForResult());
+    EXPECT_EQ(OK, req_a[i]->WaitForResult());
+  }
+}
+
 TEST_F(ClientSocketPoolBaseTest,
        ReleasingDisconnectedSocketsMaintainsPriorityOrder) {
   CreatePool(kDefaultMaxSockets, kDefaultMaxSocketsPerGroup);