Merge bitcoin/bitcoin#35723: fuzz: Drop unnecessary mutexes

240d5f7 fuzz: Drop unnecessary mutexes (marcofleon)

Pull request description:

  Quick cleanup addressing bitcoin/bitcoin#35295 (comment).

  This follows the same logic as 48df093 from bitcoin/bitcoin#35521.

ACKs for top commit:
  maflcko:
    lgtm ACK 240d5f7
  nervana21:
    ACK 240d5f7
  l0rinc:
    code review ACK 240d5f7

Tree-SHA512: 869127dc8cec4fc0688f92d67dc22f643cf3741c62d645eb4a959a9d8f46590efe19765f7df97ee36f9a3ca759c50fe983a3e6655e40a53ea99904e7a1ec00f6

Author: fanquake

src/test/fuzz/coins_view.cpp

@@ -91,11 +91,9 @@ class MutationGuardCoinsViewCache final : public CCoinsViewCache
 // Reuse a single global thread pool across fuzz iterations. Creating and destroying a pool every
 // iteration leaks memory, since iterations can run faster than the OS can tear down the threads.
 std::shared_ptr<ThreadPool> g_thread_pool{std::make_shared<ThreadPool>("view_fuzz")};
-Mutex g_thread_pool_mutex;
 
-void StartPoolIfNeeded() EXCLUSIVE_LOCKS_REQUIRED(!g_thread_pool_mutex)
+void StartPoolIfNeeded()
 {
-    LOCK(g_thread_pool_mutex);
     if (!g_thread_pool->WorkersCount()) g_thread_pool->Start(DEFAULT_PREVOUTFETCH_THREADS);
 }
 
@@ -436,7 +434,7 @@ FUZZ_TARGET(coins_view_db, .init = initialize_coins_view)
 // This allows us to exercise all methods on a CoinsViewOverlay, while also
 // ensuring that nothing can mutate the underlying cache until Flush or Sync is
 // called.
-FUZZ_TARGET(coins_view_overlay, .init = initialize_coins_view) EXCLUSIVE_LOCKS_REQUIRED(!g_thread_pool_mutex)
+FUZZ_TARGET(coins_view_overlay, .init = initialize_coins_view)
 {
     SeedRandomStateForTest(SeedRand::ZEROS); // for SaltedTxidHasher
     StartPoolIfNeeded();
@@ -448,7 +446,7 @@ FUZZ_TARGET(coins_view_overlay, .init = initialize_coins_view) EXCLUSIVE_LOCKS_R
     TestCoinsView(fuzzed_data_provider, coins_view_cache, &backend_cache);
 }
 
-FUZZ_TARGET(coins_view_stacked, .init = initialize_coins_view) EXCLUSIVE_LOCKS_REQUIRED(!g_thread_pool_mutex)
+FUZZ_TARGET(coins_view_stacked, .init = initialize_coins_view)
 {
     SeedRandomStateForTest(SeedRand::ZEROS); // for SaltedTxidHasher
     StartPoolIfNeeded();

src/test/fuzz/coinscache_sim.cpp

@@ -207,17 +207,15 @@ struct OverlayFetchScope
 // Reuse a single global thread pool across fuzz iterations. Creating and destroying a pool every
 // iteration leaks memory, since iterations can run faster than the OS can tear down the threads.
 std::shared_ptr<ThreadPool> g_thread_pool{std::make_shared<ThreadPool>("cache_fuzz")};
-Mutex g_thread_pool_mutex;
 
-void StartPoolIfNeeded() EXCLUSIVE_LOCKS_REQUIRED(!g_thread_pool_mutex)
+void StartPoolIfNeeded()
 {
-    LOCK(g_thread_pool_mutex);
     if (!g_thread_pool->WorkersCount()) g_thread_pool->Start(DEFAULT_PREVOUTFETCH_THREADS);
 }
 
 } // namespace
 
-FUZZ_TARGET(coinscache_sim, .init = [] { static auto setup{MakeNoLogFileContext<>()}; }) EXCLUSIVE_LOCKS_REQUIRED(!g_thread_pool_mutex)
+FUZZ_TARGET(coinscache_sim, .init = [] { static auto setup{MakeNoLogFileContext<>()}; })
 {
     SeedRandomStateForTest(SeedRand::ZEROS);
     StartPoolIfNeeded();