From 5bc5156b06716e8b50cb0460fb1b2d3fa088eedf Mon Sep 17 00:00:00 2001
From: Sergey Kolomenkin <s.kolomenkin@gaijin.team>
Date: Mon, 15 May 2023 16:57:42 +0400
Subject: [PATCH] fix race condition causing unexpected delay during connection
 close

It happens when connection close was started and it signaled
conditional variable before waiting for the same variable
was started in reconnect thread.

The code example to reproduce the problem:
```c++
int main()
{
  printf("Begin...\n");
  natsConnection * connection = nullptr;
  natsOptions * options = nullptr;
  constexpr auto onConnectHandler = [](natsConnection *, void *)
  {
  };

  natsOptions_Create(&options);
  natsOptions_SetRetryOnFailedConnect(options, true, onConnectHandler, nullptr);
  natsOptions_SetURL(options, "nats://localhost:54321");

  const auto ts1 = nats_Now();
  const natsStatus err = natsConnection_Connect(&connection, options);
  const auto ts2 = nats_Now();

  if (err == NATS_NOT_YET_CONNECTED || err == NATS_OK)
  {
    natsConnection_Close(connection);
  }
  const auto ts3 = nats_Now();

  printf("connection err code: %s\n", natsStatus_GetText(err));
  printf("Connect took: %lld ms\n", (ts2 - ts1));
  printf("Connection close took: %lld ms\n", (ts3 - ts2));
  return 0;
}
```

Program output:
```
Begin...
connection err code: Not Yet Connected
Connect took: 2017 ms
Connection close took: 2057 ms
```

Here we are connecting to a NATS server which is offline.
NATS_NOT_YET_CONNECTED status is returned.
We have 2 seconds before next connection try.
I expect connection to close very fast.
But closing freezes for these 2 seconds.
---
 src/conn.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/conn.c b/src/conn.c
index b769a7711..8e7d66deb 100644
--- a/src/conn.c
+++ b/src/conn.c
@@ -1581,8 +1581,6 @@ _doReconnect(void *arg)
                 natsConn_Unlock(nc);
                 sleepTime = crd(nc, wlf, crdClosure);
                 natsConn_Lock(nc);
-                if (natsConn_isClosed(nc))
-                    break;
             }
             else
             {
@@ -1590,6 +1588,8 @@ _doReconnect(void *arg)
                 if (jitter > 0)
                     sleepTime += rand() % jitter;
             }
+            if (natsConn_isClosed(nc))
+                break;
             natsCondition_TimedWait(nc->reconnectCond, nc->mu, sleepTime);
         }
         else