Merge pull request #1649 from sheremetyev/fix-pipe-activation-race

Fix pipe activation race

src/pipe.cpp

@@ -460,14 +460,9 @@ int zmq::pipe_t::compute_lwm (int hwm_)
     //     result in low performance.
     //
     //  Given the 3. it would be good to keep HWM and LWM as far apart as
-    //  possible to reduce the thread switching overhead to almost zero,
-    //  say HWM-LWM should be max_wm_delta.
-    //
-    //  That done, we still we have to account for the cases where
-    //  HWM < max_wm_delta thus driving LWM to negative numbers.
-    //  Let's make LWM 1/2 of HWM in such cases.
-    int result = (hwm_ > max_wm_delta * 2) ?
-        hwm_ - max_wm_delta : (hwm_ + 1) / 2;
+    //  possible to reduce the thread switching overhead to almost zero.
+    //  Let's make LWM 1/2 of HWM.
+    int result = (hwm_ + 1) / 2;
 
     return result;
 }

tests/test_hwm_pubsub.cpp

@@ -151,7 +151,81 @@ int test_blocking (int send_hwm, int msgCnt)
     return recv_count;
 }
 
+// with hwm 11024: send 9999 msg, receive 9999, send 1100, receive 1100
+void test_reset_hwm ()
+{
+    int first_count = 9999;
+    int second_count = 1100;
+    int hwm = 11024;
+
+    void *ctx = zmq_ctx_new ();
+    assert (ctx);
+    int rc;
+
+    // Set up bind socket
+    void *pub_socket = zmq_socket (ctx, ZMQ_PUB);
+    assert (pub_socket);
+    rc = zmq_setsockopt (pub_socket, ZMQ_SNDHWM, &hwm, sizeof (hwm));
+    assert (rc == 0);
+    rc = zmq_bind (pub_socket, "tcp://127.0.0.1:1234");
+    assert (rc == 0);
+
+    // Set up connect socket
+    void *sub_socket = zmq_socket (ctx, ZMQ_SUB);
+    assert (sub_socket);
+    rc = zmq_setsockopt (sub_socket, ZMQ_RCVHWM, &hwm, sizeof (hwm));
+    assert (rc == 0);
+    rc = zmq_connect (sub_socket, "tcp://127.0.0.1:1234");
+    assert (rc == 0);
+    rc = zmq_setsockopt( sub_socket, ZMQ_SUBSCRIBE, 0, 0);
+    assert (rc == 0);
+
+    msleep (100);
+
+    // Send messages
+    int send_count = 0;
+    while (send_count < first_count && zmq_send (pub_socket, NULL, 0, ZMQ_DONTWAIT) == 0)
+        ++send_count;
+    assert (first_count == send_count);
+
+    msleep (100);
+
+    // Now receive all sent messages
+    int recv_count = 0;
+    while (0 == zmq_recv (sub_socket, NULL, 0, ZMQ_DONTWAIT))
+    {
+        ++recv_count;
+    }
+    assert (first_count == recv_count);
+
+    msleep (100);
+
+    // Send messages
+    send_count = 0;
+    while (send_count < second_count && zmq_send (pub_socket, NULL, 0, ZMQ_DONTWAIT) == 0)
+        ++send_count;
+    assert (second_count == send_count);
+
+    msleep (100);
+
+    // Now receive all sent messages
+    recv_count = 0;
+    while (0 == zmq_recv (sub_socket, NULL, 0, ZMQ_DONTWAIT))
+    {
+        ++recv_count;
+    }
+    assert (second_count == recv_count);
 
+    // Clean up
+    rc = zmq_close (sub_socket);
+    assert (rc == 0);
+
+    rc = zmq_close (pub_socket);
+    assert (rc == 0);
+
+    rc = zmq_ctx_term (ctx);
+    assert (rc == 0);
+}
 
 int main (void)
 {
@@ -167,5 +241,8 @@ int main (void)
     count = test_blocking (2000,6000);
     assert (count == 6000);
 
+    // hwm should apply to the messages that have already been received
+    test_reset_hwm ();
+
     return 0;
 }