Merge #15849: Thread names in logs and deadlock debug tools

8722e54e56 threads: add thread names to deadlock debugging message (James O'Beirne)
383b186c28 threads: prefix log messages with thread names (James O'Beirne)
ddd95ccb80 tests: add threadutil tests (James O'Beirne)
ae5f2b6a6c threads: introduce util/threadnames, refactor thread naming (James O'Beirne)
188ca75e5f disable HAVE_THREAD_LOCAL on unreliable platforms (James O'Beirne)

Pull request description:

  I'm resurrecting this one (from #13168) because I need it to make progress on #15735.

  It's now off by default and can be turned on with `-logthreadnames=1`.

  Ran some benchmarks (IBD from local peer from 500_000 -> 504_000) and it's within spitting distance either on or off:

  ### threadnames off (default)

  #### 2018-05-threadnames.3 vs. master (absolute)
  |                      name                      | iterations |   2018-05-threadnames.3    |           master           |
  |------------------------------------------------|-----------:|----------------------------|----------------------------|
  | ibd.local.500000.504000.dbcache=2048           |          3 | 376.1584 (± 9.2944)        | 392.3414 (± 13.4238)       |
  | ibd.local.500000.504000.dbcache=2048.mem-usage |          3 | 2236117.3333 (± 1845.9623) | 2238690.6667 (± 2669.3487) |

  #### 2018-05-threadnames.3 vs. master (relative)
  |                      name                      | iterations | 2018-05-threadnames.3 | master |
  |------------------------------------------------|-----------:|----------------------:|-------:|
  | ibd.local.500000.504000.dbcache=2048           |          3 |                     1 |  1.043 |
  | ibd.local.500000.504000.dbcache=2048.mem-usage |          3 |                     1 |  1.001 |

  ### threadnames on

  #### 2018-05-threadnames-take-2 vs. master (absolute)
  |                      name                      | iterations | 2018-05-threadnames-take-2 |           master           |
  |------------------------------------------------|-----------:|----------------------------|----------------------------|
  | ibd.local.500000.504000.dbcache=2048           |          3 | 367.6861 (± 0.3941)        | 364.1667 (± 0.9776)        |
  | ibd.local.500000.504000.dbcache=2048.mem-usage |          3 | 2238461.3333 (± 3697.8730) | 2237014.6667 (± 3307.6966) |

  #### 2018-05-threadnames-take-2 vs. master (relative)
  |                      name                      | iterations | 2018-05-threadnames-take-2 | master |
  |------------------------------------------------|-----------:|---------------------------:|-------:|
  | ibd.local.500000.504000.dbcache=2048           |          3 |                      1.010 |   1.00 |
  | ibd.local.500000.504000.dbcache=2048.mem-usage |          3 |                      1.001 |   1.00 |
  ```

ACKs for commit 8722e5:
  Empact:
    utACK 8722e54e56
  jnewbery:
    utACK 8722e54e56
  MarcoFalke:
    re-utACK 8722e54e56 (Only change since my previous review is DEFAULT_LOGTHREADNAMES=false and stylistic updates

Tree-SHA512: 50af992708295b8d680cf10025262dd964e599a356bdfc1dfc84fb18c00afabcb34d3d12d551b0677ff81f8fccad0e17c1d5b24dfecb953a913bc77fdd1a4577

src/test/setup_common.cpp

@@ -94,7 +94,7 @@ TestingSetup::TestingSetup(const std::string& chainName) : BasicTestingSetup(cha
 
     nScriptCheckThreads = 3;
     for (int i = 0; i < nScriptCheckThreads - 1; i++)
-        threadGroup.create_thread(&ThreadScriptCheck);
+        threadGroup.create_thread([i]() { return ThreadScriptCheck(i); });
 
     g_banman = MakeUnique<BanMan>(GetDataDir() / "banlist.dat", nullptr, DEFAULT_MISBEHAVING_BANTIME);
     g_connman = MakeUnique<CConnman>(0x1337, 0x1337); // Deterministic randomness for tests.

src/test/util_threadnames_tests.cpp

@@ -0,0 +1,73 @@
+// Copyright (c) 2018 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <util/threadnames.h>
+#include <test/setup_common.h>
+
+#include <thread>
+#include <vector>
+#include <set>
+#include <mutex>
+
+#if defined(HAVE_CONFIG_H)
+#include <config/bitcoin-config.h>
+#endif
+
+#include <boost/test/unit_test.hpp>
+
+BOOST_FIXTURE_TEST_SUITE(util_threadnames_tests, BasicTestingSetup)
+
+const std::string TEST_THREAD_NAME_BASE = "test_thread.";
+
+/**
+ * Run a bunch of threads to all call util::ThreadRename.
+ *
+ * @return the set of name each thread has after attempted renaming.
+ */
+std::set<std::string> RenameEnMasse(int num_threads)
+{
+    std::vector<std::thread> threads;
+    std::set<std::string> names;
+    std::mutex lock;
+
+    auto RenameThisThread = [&](int i) {
+        util::ThreadRename(TEST_THREAD_NAME_BASE + std::to_string(i));
+        std::lock_guard<std::mutex> guard(lock);
+        names.insert(util::ThreadGetInternalName());
+    };
+
+    for (int i = 0; i < num_threads; ++i) {
+        threads.push_back(std::thread(RenameThisThread, i));
+    }
+
+    for (std::thread& thread : threads) thread.join();
+
+    return names;
+}
+
+/**
+ * Rename a bunch of threads with the same basename (expect_multiple=true), ensuring suffixes are
+ * applied properly.
+ */
+BOOST_AUTO_TEST_CASE(util_threadnames_test_rename_threaded)
+{
+    BOOST_CHECK_EQUAL(util::ThreadGetInternalName(), "");
+
+#if !defined(HAVE_THREAD_LOCAL)
+    // This test doesn't apply to platforms where we don't have thread_local.
+    return;
+#endif
+
+    std::set<std::string> names = RenameEnMasse(100);
+
+    BOOST_CHECK_EQUAL(names.size(), 100);
+
+    // Names "test_thread.[n]" should exist for n = [0, 99]
+    for (int i = 0; i < 100; ++i) {
+        BOOST_CHECK(names.find(TEST_THREAD_NAME_BASE + std::to_string(i)) != names.end());
+    }
+
+}
+
+BOOST_AUTO_TEST_SUITE_END()