tests: Fix lock-order-inversion (potential deadlock) in DoS_tests. Reported by TSAN.

Makes `src/test/test_bitcoin --run_test=DoS_tests` pass also when
compiled with TreadSanitizer (`./configure --with-sanitizers=thread`).

src/net_processing.h

@@ -77,7 +77,7 @@ public:
     * @param[in]   interrupt       Interrupt condition for processing threads
     * @return                      True if there is more work to be done
     */
-    bool SendMessages(CNode* pto, std::atomic<bool>& interrupt) override;
+    bool SendMessages(CNode* pto, std::atomic<bool>& interrupt) override EXCLUSIVE_LOCKS_REQUIRED(pto->cs_sendProcessing);
 
     /** Consider evicting an outbound peer based on the amount of time they've been behind our tip */
     void ConsiderEviction(CNode *pto, int64_t time_in_seconds);

src/test/denialofservice_tests.cpp

@@ -66,25 +66,40 @@ BOOST_AUTO_TEST_CASE(outbound_slow_chain_eviction)
     dummyNode1.fSuccessfullyConnected = true;
 
     // This test requires that we have a chain with non-zero work.
-    LOCK(cs_main);
-    BOOST_CHECK(chainActive.Tip() != nullptr);
-    BOOST_CHECK(chainActive.Tip()->nChainWork > 0);
+    {
+        LOCK(cs_main);
+        BOOST_CHECK(chainActive.Tip() != nullptr);
+        BOOST_CHECK(chainActive.Tip()->nChainWork > 0);
+    }
 
     // Test starts here
-    LOCK(dummyNode1.cs_sendProcessing);
-    peerLogic->SendMessages(&dummyNode1, interruptDummy); // should result in getheaders
-    LOCK(dummyNode1.cs_vSend);
-    BOOST_CHECK(dummyNode1.vSendMsg.size() > 0);
-    dummyNode1.vSendMsg.clear();
+    {
+        LOCK2(cs_main, dummyNode1.cs_sendProcessing);
+        peerLogic->SendMessages(&dummyNode1, interruptDummy); // should result in getheaders
+    }
+    {
+        LOCK2(cs_main, dummyNode1.cs_vSend);
+        BOOST_CHECK(dummyNode1.vSendMsg.size() > 0);
+        dummyNode1.vSendMsg.clear();
+    }
 
     int64_t nStartTime = GetTime();
     // Wait 21 minutes
     SetMockTime(nStartTime+21*60);
-    peerLogic->SendMessages(&dummyNode1, interruptDummy); // should result in getheaders
-    BOOST_CHECK(dummyNode1.vSendMsg.size() > 0);
+    {
+        LOCK2(cs_main, dummyNode1.cs_sendProcessing);
+        peerLogic->SendMessages(&dummyNode1, interruptDummy); // should result in getheaders
+    }
+    {
+        LOCK2(cs_main, dummyNode1.cs_vSend);
+        BOOST_CHECK(dummyNode1.vSendMsg.size() > 0);
+    }
     // Wait 3 more minutes
     SetMockTime(nStartTime+24*60);
-    peerLogic->SendMessages(&dummyNode1, interruptDummy); // should result in disconnect
+    {
+        LOCK2(cs_main, dummyNode1.cs_sendProcessing);
+        peerLogic->SendMessages(&dummyNode1, interruptDummy); // should result in disconnect
+    }
     BOOST_CHECK(dummyNode1.fDisconnect == true);
     SetMockTime(0);
 
@@ -190,8 +205,10 @@ BOOST_AUTO_TEST_CASE(DoS_banning)
         LOCK(cs_main);
         Misbehaving(dummyNode1.GetId(), 100); // Should get banned
     }
-    LOCK(dummyNode1.cs_sendProcessing);
-    peerLogic->SendMessages(&dummyNode1, interruptDummy);
+    {
+        LOCK2(cs_main, dummyNode1.cs_sendProcessing);
+        peerLogic->SendMessages(&dummyNode1, interruptDummy);
+    }
     BOOST_CHECK(connman->IsBanned(addr1));
     BOOST_CHECK(!connman->IsBanned(ip(0xa0b0c001|0x0000ff00))); // Different IP, not banned
 
@@ -205,15 +222,20 @@ BOOST_AUTO_TEST_CASE(DoS_banning)
         LOCK(cs_main);
         Misbehaving(dummyNode2.GetId(), 50);
     }
-    LOCK(dummyNode2.cs_sendProcessing);
-    peerLogic->SendMessages(&dummyNode2, interruptDummy);
+    {
+        LOCK2(cs_main, dummyNode2.cs_sendProcessing);
+        peerLogic->SendMessages(&dummyNode2, interruptDummy);
+    }
     BOOST_CHECK(!connman->IsBanned(addr2)); // 2 not banned yet...
     BOOST_CHECK(connman->IsBanned(addr1));  // ... but 1 still should be
     {
         LOCK(cs_main);
         Misbehaving(dummyNode2.GetId(), 50);
     }
-    peerLogic->SendMessages(&dummyNode2, interruptDummy);
+    {
+        LOCK2(cs_main, dummyNode2.cs_sendProcessing);
+        peerLogic->SendMessages(&dummyNode2, interruptDummy);
+    }
     BOOST_CHECK(connman->IsBanned(addr2));
 
     bool dummy;
@@ -237,20 +259,28 @@ BOOST_AUTO_TEST_CASE(DoS_banscore)
         LOCK(cs_main);
         Misbehaving(dummyNode1.GetId(), 100);
     }
-    LOCK(dummyNode1.cs_sendProcessing);
-    peerLogic->SendMessages(&dummyNode1, interruptDummy);
+    {
+        LOCK2(cs_main, dummyNode1.cs_sendProcessing);
+        peerLogic->SendMessages(&dummyNode1, interruptDummy);
+    }
     BOOST_CHECK(!connman->IsBanned(addr1));
     {
         LOCK(cs_main);
         Misbehaving(dummyNode1.GetId(), 10);
     }
-    peerLogic->SendMessages(&dummyNode1, interruptDummy);
+    {
+        LOCK2(cs_main, dummyNode1.cs_sendProcessing);
+        peerLogic->SendMessages(&dummyNode1, interruptDummy);
+    }
     BOOST_CHECK(!connman->IsBanned(addr1));
     {
         LOCK(cs_main);
         Misbehaving(dummyNode1.GetId(), 1);
     }
-    peerLogic->SendMessages(&dummyNode1, interruptDummy);
+    {
+        LOCK2(cs_main, dummyNode1.cs_sendProcessing);
+        peerLogic->SendMessages(&dummyNode1, interruptDummy);
+    }
     BOOST_CHECK(connman->IsBanned(addr1));
     gArgs.ForceSetArg("-banscore", std::to_string(DEFAULT_BANSCORE_THRESHOLD));
 
@@ -277,8 +307,10 @@ BOOST_AUTO_TEST_CASE(DoS_bantime)
         LOCK(cs_main);
         Misbehaving(dummyNode.GetId(), 100);
     }
-    LOCK(dummyNode.cs_sendProcessing);
-    peerLogic->SendMessages(&dummyNode, interruptDummy);
+    {
+        LOCK2(cs_main, dummyNode.cs_sendProcessing);
+        peerLogic->SendMessages(&dummyNode, interruptDummy);
+    }
     BOOST_CHECK(connman->IsBanned(addr));
 
     SetMockTime(nStartTime+60*60);