Fix potential deadlock

Conflict:
* cs_main in ProcessMessages() (before calling ProcessMessages)
* cs_vSend in CNode::BeginMessage
versus:
* cs_vSend in ThreadMessageHandler2 (before calling SendMessages)
* cs_main in SendMessages

Even though cs_vSend is a try_lock, if it succeeds simultaneously with
the locking of cs_main in ProcessMessages(), it could cause a deadlock.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/main.cpp b/src/main.cpp
index f2932804e3..3396fe1911 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -2807,8 +2807,8 @@ bool ProcessMessages(CNode* pfrom)
 
 bool SendMessages(CNode* pto, bool fSendTrickle)
 {
-    {
-        LOCK(cs_main);
+    TRY_LOCK(cs_main, lockMain);
+    if (lockMain) {
         // Don't send anything until we get their version message
         if (pto->nVersion == 0)
             return true;