Misc fixes and improvements to thread pool

tests/tests.cpp

@@ -2,6 +2,12 @@
 
 #include "config.hpp"
 #include "str.hpp"
+#include "thread_pool.hpp"
+
+#include <atomic>
+#include <chrono>
+#include <numeric>
+#include <thread>
 
 void
 test_nop()
@@ -481,6 +487,517 @@ test_config()
   TEST_CHECK(cfg.set("async-read","true") == 0);
 }
 
+// =====================================================================
+// ThreadPool tests
+// =====================================================================
+
+void
+test_tp_construct_default()
+{
+  ThreadPool tp(2, 4, "test.default");
+
+  auto threads = tp.threads();
+
+  TEST_CHECK(threads.size() == 2);
+}
+
+void
+test_tp_construct_named()
+{
+  ThreadPool tp(1, 2, "test.named");
+
+  auto threads = tp.threads();
+
+  TEST_CHECK(threads.size() == 1);
+}
+
+void
+test_tp_construct_zero_threads_throws()
+{
+  bool threw = false;
+
+  try
+    {
+      ThreadPool tp(0, 4, "test.zero");
+    }
+  catch(const std::runtime_error &)
+    {
+      threw = true;
+    }
+
+  TEST_CHECK(threw);
+}
+
+void
+test_tp_enqueue_work()
+{
+  ThreadPool tp(2, 4, "test.ew");
+
+  std::atomic<int> counter{0};
+
+  for(int i = 0; i < 10; ++i)
+    tp.enqueue_work([&counter](){ counter.fetch_add(1); });
+
+  // wait for completion
+  for(int i = 0; i < 1000 && counter.load() < 10; ++i)
+    std::this_thread::sleep_for(std::chrono::milliseconds(1));
+
+  TEST_CHECK(counter.load() == 10);
+}
+
+void
+test_tp_enqueue_work_with_ptoken()
+{
+  ThreadPool tp(2, 4, "test.ewp");
+
+  std::atomic<int> counter{0};
+  auto ptok = tp.ptoken();
+
+  for(int i = 0; i < 10; ++i)
+    tp.enqueue_work(ptok, [&counter](){ counter.fetch_add(1); });
+
+  for(int i = 0; i < 1000 && counter.load() < 10; ++i)
+    std::this_thread::sleep_for(std::chrono::milliseconds(1));
+
+  TEST_CHECK(counter.load() == 10);
+}
+
+void
+test_tp_try_enqueue_work()
+{
+  // Use 1 thread and a small queue depth of 2
+  ThreadPool tp(1, 2, "test.tew");
+
+  std::atomic<int> counter{0};
+
+  // These should succeed (queue has room)
+  bool ok = tp.try_enqueue_work([&counter](){ counter.fetch_add(1); });
+  TEST_CHECK(ok);
+
+  for(int i = 0; i < 1000 && counter.load() < 1; ++i)
+    std::this_thread::sleep_for(std::chrono::milliseconds(1));
+
+  TEST_CHECK(counter.load() == 1);
+}
+
+void
+test_tp_try_enqueue_work_with_ptoken()
+{
+  ThreadPool tp(1, 2, "test.tewp");
+
+  std::atomic<int> counter{0};
+  auto ptok = tp.ptoken();
+
+  bool ok = tp.try_enqueue_work(ptok, [&counter](){ counter.fetch_add(1); });
+  TEST_CHECK(ok);
+
+  for(int i = 0; i < 1000 && counter.load() < 1; ++i)
+    std::this_thread::sleep_for(std::chrono::milliseconds(1));
+
+  TEST_CHECK(counter.load() == 1);
+}
+
+void
+test_tp_try_enqueue_work_for()
+{
+  ThreadPool tp(1, 2, "test.tewf");
+
+  std::atomic<int> counter{0};
+
+  bool ok = tp.try_enqueue_work_for(100000, // 100ms
+                                    [&counter](){ counter.fetch_add(1); });
+  TEST_CHECK(ok);
+
+  for(int i = 0; i < 1000 && counter.load() < 1; ++i)
+    std::this_thread::sleep_for(std::chrono::milliseconds(1));
+
+  TEST_CHECK(counter.load() == 1);
+}
+
+void
+test_tp_try_enqueue_work_for_with_ptoken()
+{
+  ThreadPool tp(1, 2, "test.tewfp");
+
+  std::atomic<int> counter{0};
+  auto ptok = tp.ptoken();
+
+  bool ok = tp.try_enqueue_work_for(ptok,
+                                    100000, // 100ms
+                                    [&counter](){ counter.fetch_add(1); });
+  TEST_CHECK(ok);
+
+  for(int i = 0; i < 1000 && counter.load() < 1; ++i)
+    std::this_thread::sleep_for(std::chrono::milliseconds(1));
+
+  TEST_CHECK(counter.load() == 1);
+}
+
+void
+test_tp_enqueue_task_int()
+{
+  ThreadPool tp(2, 4, "test.eti");
+
+  auto future = tp.enqueue_task([]() -> int { return 42; });
+
+  TEST_CHECK(future.get() == 42);
+}
+
+void
+test_tp_enqueue_task_void()
+{
+  ThreadPool tp(2, 4, "test.etv");
+
+  std::atomic<bool> ran{false};
+
+  auto future = tp.enqueue_task([&ran]() { ran.store(true); });
+
+  future.get(); // should not throw
+
+  TEST_CHECK(ran.load());
+}
+
+void
+test_tp_enqueue_task_string()
+{
+  ThreadPool tp(2, 4, "test.ets");
+
+  auto future = tp.enqueue_task([]() -> std::string { return "hello"; });
+
+  TEST_CHECK(future.get() == "hello");
+}
+
+void
+test_tp_enqueue_task_exception()
+{
+  ThreadPool tp(2, 4, "test.ete");
+
+  auto future = tp.enqueue_task([]() -> int
+    {
+      throw std::runtime_error("task error");
+      return 0;
+    });
+
+  bool caught = false;
+
+  try
+    {
+      future.get();
+    }
+  catch(const std::runtime_error &e)
+    {
+      caught = true;
+      TEST_CHECK(std::string(e.what()) == "task error");
+    }
+
+  TEST_CHECK(caught);
+}
+
+void
+test_tp_threads_returns_correct_count()
+{
+  ThreadPool tp(4, 8, "test.thr");
+
+  auto threads = tp.threads();
+
+  TEST_CHECK(threads.size() == 4);
+
+  // All thread IDs should be non-zero
+  for(auto t : threads)
+    TEST_CHECK(t != 0);
+}
+
+void
+test_tp_threads_unique_ids()
+{
+  ThreadPool tp(4, 8, "test.uid");
+
+  auto threads = tp.threads();
+
+  // All thread IDs should be unique
+  for(std::size_t i = 0; i < threads.size(); ++i)
+    for(std::size_t j = i + 1; j < threads.size(); ++j)
+      TEST_CHECK(threads[i] != threads[j]);
+}
+
+void
+test_tp_add_thread()
+{
+  ThreadPool tp(2, 4, "test.add");
+
+  TEST_CHECK(tp.threads().size() == 2);
+
+  int rv = tp.add_thread();
+
+  TEST_CHECK(rv == 0);
+  TEST_CHECK(tp.threads().size() == 3);
+}
+
+void
+test_tp_remove_thread()
+{
+  ThreadPool tp(3, 4, "test.rm");
+
+  TEST_CHECK(tp.threads().size() == 3);
+
+  int rv = tp.remove_thread();
+
+  TEST_CHECK(rv == 0);
+  TEST_CHECK(tp.threads().size() == 2);
+}
+
+void
+test_tp_remove_thread_refuses_last()
+{
+  ThreadPool tp(1, 4, "test.rmlast");
+
+  TEST_CHECK(tp.threads().size() == 1);
+
+  int rv = tp.remove_thread();
+
+  TEST_CHECK(rv == -EINVAL);
+  TEST_CHECK(tp.threads().size() == 1);
+}
+
+void
+test_tp_set_threads_grow()
+{
+  ThreadPool tp(2, 8, "test.grow");
+
+  TEST_CHECK(tp.threads().size() == 2);
+
+  int rv = tp.set_threads(4);
+
+  TEST_CHECK(rv == 0);
+  TEST_CHECK(tp.threads().size() == 4);
+}
+
+void
+test_tp_set_threads_shrink()
+{
+  ThreadPool tp(4, 8, "test.shrink");
+
+  TEST_CHECK(tp.threads().size() == 4);
+
+  int rv = tp.set_threads(2);
+
+  TEST_CHECK(rv == 0);
+  TEST_CHECK(tp.threads().size() == 2);
+}
+
+void
+test_tp_set_threads_zero()
+{
+  ThreadPool tp(2, 4, "test.sz");
+
+  int rv = tp.set_threads(0);
+
+  TEST_CHECK(rv == -EINVAL);
+  TEST_CHECK(tp.threads().size() == 2);
+}
+
+void
+test_tp_set_threads_same()
+{
+  ThreadPool tp(3, 4, "test.same");
+
+  int rv = tp.set_threads(3);
+
+  TEST_CHECK(rv == 0);
+  TEST_CHECK(tp.threads().size() == 3);
+}
+
+void
+test_tp_work_after_add_thread()
+{
+  ThreadPool tp(1, 4, "test.waat");
+
+  tp.add_thread();
+  tp.add_thread();
+
+  std::atomic<int> counter{0};
+  const int N = 20;
+
+  for(int i = 0; i < N; ++i)
+    tp.enqueue_work([&counter](){ counter.fetch_add(1); });
+
+  for(int i = 0; i < 2000 && counter.load() < N; ++i)
+    std::this_thread::sleep_for(std::chrono::milliseconds(1));
+
+  TEST_CHECK(counter.load() == N);
+}
+
+void
+test_tp_work_after_remove_thread()
+{
+  ThreadPool tp(3, 4, "test.wart");
+
+  tp.remove_thread();
+
+  std::atomic<int> counter{0};
+  const int N = 10;
+
+  for(int i = 0; i < N; ++i)
+    tp.enqueue_work([&counter](){ counter.fetch_add(1); });
+
+  for(int i = 0; i < 2000 && counter.load() < N; ++i)
+    std::this_thread::sleep_for(std::chrono::milliseconds(1));
+
+  TEST_CHECK(counter.load() == N);
+}
+
+void
+test_tp_worker_exception_no_crash()
+{
+  ThreadPool tp(2, 4, "test.exc");
+
+  // Enqueue work that throws -- pool should not crash
+  tp.enqueue_work([](){
+    throw std::runtime_error("deliberate error");
+  });
+
+  // Enqueue normal work after the exception
+  std::atomic<bool> ran{false};
+  tp.enqueue_work([&ran](){ ran.store(true); });
+
+  for(int i = 0; i < 1000 && !ran.load(); ++i)
+    std::this_thread::sleep_for(std::chrono::milliseconds(1));
+
+  TEST_CHECK(ran.load());
+}
+
+void
+test_tp_concurrent_enqueue()
+{
+  ThreadPool tp(4, 64, "test.conc");
+
+  std::atomic<int> counter{0};
+  const int PRODUCERS = 4;
+  const int ITEMS_PER = 50;
+  const int TOTAL = PRODUCERS * ITEMS_PER;
+
+  std::vector<std::thread> producers;
+  for(int p = 0; p < PRODUCERS; ++p)
+    {
+      producers.emplace_back([&tp, &counter]()
+        {
+          auto ptok = tp.ptoken();
+          for(int i = 0; i < ITEMS_PER; ++i)
+            tp.enqueue_work(ptok, [&counter](){ counter.fetch_add(1); });
+        });
+    }
+
+  for(auto &t : producers)
+    t.join();
+
+  for(int i = 0; i < 5000 && counter.load() < TOTAL; ++i)
+    std::this_thread::sleep_for(std::chrono::milliseconds(1));
+
+  TEST_CHECK(counter.load() == TOTAL);
+}
+
+void
+test_tp_enqueue_task_multiple()
+{
+  ThreadPool tp(4, 16, "test.etm");
+
+  std::vector<std::future<int>> futures;
+  const int N = 20;
+
+  for(int i = 0; i < N; ++i)
+    futures.push_back(tp.enqueue_task([i]() -> int { return i * i; }));
+
+  for(int i = 0; i < N; ++i)
+    TEST_CHECK(futures[i].get() == i * i);
+}
+
+void
+test_tp_ptoken_creation()
+{
+  ThreadPool tp(2, 4, "test.ptok");
+
+  // Multiple ptokens should be independently usable
+  auto ptok1 = tp.ptoken();
+  auto ptok2 = tp.ptoken();
+
+  std::atomic<int> counter{0};
+
+  tp.enqueue_work(ptok1, [&counter](){ counter.fetch_add(1); });
+  tp.enqueue_work(ptok2, [&counter](){ counter.fetch_add(1); });
+
+  for(int i = 0; i < 1000 && counter.load() < 2; ++i)
+    std::this_thread::sleep_for(std::chrono::milliseconds(1));
+
+  TEST_CHECK(counter.load() == 2);
+}
+
+void
+test_tp_destruction_drains_queue()
+{
+  std::atomic<int> counter{0};
+
+  {
+    ThreadPool tp(2, 64, "test.drain");
+
+    for(int i = 0; i < 50; ++i)
+      tp.enqueue_work([&counter](){
+        counter.fetch_add(1);
+      });
+
+    // destructor runs here -- should drain all queued work
+  }
+
+  TEST_CHECK(counter.load() == 50);
+}
+
+void
+test_tp_move_only_callable()
+{
+  ThreadPool tp(2, 4, "test.moc");
+
+  auto ptr = std::make_unique<int>(99);
+
+  auto future = tp.enqueue_task([p = std::move(ptr)]() -> int
+    {
+      return *p;
+    });
+
+  TEST_CHECK(future.get() == 99);
+}
+
+void
+test_tp_work_ordering_single_thread()
+{
+  // With a single thread, work should execute in FIFO order
+  ThreadPool tp(1, 16, "test.order");
+
+  std::vector<int> results;
+  std::mutex mtx;
+  const int N = 10;
+
+  for(int i = 0; i < N; ++i)
+    tp.enqueue_work([i, &results, &mtx](){
+      std::lock_guard<std::mutex> lk(mtx);
+      results.push_back(i);
+    });
+
+  // Wait for all work to complete
+  for(int i = 0; i < 2000; ++i)
+    {
+      {
+        std::lock_guard<std::mutex> lk(mtx);
+        if((int)results.size() == N)
+          break;
+      }
+      std::this_thread::sleep_for(std::chrono::milliseconds(1));
+    }
+
+  std::lock_guard<std::mutex> lk(mtx);
+  TEST_CHECK((int)results.size() == N);
+  for(int i = 0; i < N; ++i)
+    TEST_CHECK(results[i] == i);
+}
+
 TEST_LIST =
   {
    {"nop",test_nop},
@@ -499,5 +1016,36 @@ TEST_LIST =
    {"config_xattr",test_config_xattr},
    {"config",test_config},
    {"str",test_str_stuff},
+   {"tp_construct_default",test_tp_construct_default},
+   {"tp_construct_named",test_tp_construct_named},
+   {"tp_construct_zero_threads_throws",test_tp_construct_zero_threads_throws},
+   {"tp_enqueue_work",test_tp_enqueue_work},
+   {"tp_enqueue_work_with_ptoken",test_tp_enqueue_work_with_ptoken},
+   {"tp_try_enqueue_work",test_tp_try_enqueue_work},
+   {"tp_try_enqueue_work_with_ptoken",test_tp_try_enqueue_work_with_ptoken},
+   {"tp_try_enqueue_work_for",test_tp_try_enqueue_work_for},
+   {"tp_try_enqueue_work_for_with_ptoken",test_tp_try_enqueue_work_for_with_ptoken},
+   {"tp_enqueue_task_int",test_tp_enqueue_task_int},
+   {"tp_enqueue_task_void",test_tp_enqueue_task_void},
+   {"tp_enqueue_task_string",test_tp_enqueue_task_string},
+   {"tp_enqueue_task_exception",test_tp_enqueue_task_exception},
+   {"tp_enqueue_task_multiple",test_tp_enqueue_task_multiple},
+   {"tp_threads_returns_correct_count",test_tp_threads_returns_correct_count},
+   {"tp_threads_unique_ids",test_tp_threads_unique_ids},
+   {"tp_add_thread",test_tp_add_thread},
+   {"tp_remove_thread",test_tp_remove_thread},
+   {"tp_remove_thread_refuses_last",test_tp_remove_thread_refuses_last},
+   {"tp_set_threads_grow",test_tp_set_threads_grow},
+   {"tp_set_threads_shrink",test_tp_set_threads_shrink},
+   {"tp_set_threads_zero",test_tp_set_threads_zero},
+   {"tp_set_threads_same",test_tp_set_threads_same},
+   {"tp_work_after_add_thread",test_tp_work_after_add_thread},
+   {"tp_work_after_remove_thread",test_tp_work_after_remove_thread},
+   {"tp_worker_exception_no_crash",test_tp_worker_exception_no_crash},
+   {"tp_concurrent_enqueue",test_tp_concurrent_enqueue},
+   {"tp_ptoken_creation",test_tp_ptoken_creation},
+   {"tp_destruction_drains_queue",test_tp_destruction_drains_queue},
+   {"tp_move_only_callable",test_tp_move_only_callable},
+   {"tp_work_ordering_single_thread",test_tp_work_ordering_single_thread},
    {NULL,NULL}
   };

vendored/libfuse/include/bounded_queue.hpp

@@ -0,0 +1,153 @@
+/*
+  ISC License
+
+  Copyright (c) 2026, Antonio SJ Musumeci <trapexit@spawn.link>
+
+  Permission to use, copy, modify, and/or distribute this software for any
+  purpose with or without fee is hereby granted, provided that the above
+  copyright notice and this permission notice appear in all copies.
+
+  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+
+#pragma once
+
+#include "moodycamel/blockingconcurrentqueue.h"
+#include "moodycamel/lightweightsemaphore.h"
+
+#include <cstdint>
+
+
+// Wraps an unbounded BlockingConcurrentQueue with a semaphore to enforce
+// a maximum queue depth. The semaphore tracks available slots:
+//   - Producers wait (decrement) before enqueuing, blocking when full.
+//   - Consumers signal (increment) after dequeuing, freeing a slot.
+// This co-locates the invariant so the pairing cannot drift apart.
+template<typename T, typename Traits = moodycamel::ConcurrentQueueDefaultTraits>
+class BoundedQueue
+{
+public:
+  using PToken = moodycamel::ProducerToken;
+  using CToken = moodycamel::ConsumerToken;
+
+private:
+  using Queue = moodycamel::BlockingConcurrentQueue<T,Traits>;
+
+  Queue _queue;
+  moodycamel::LightweightSemaphore _slots;
+
+public:
+  explicit
+  BoundedQueue(std::size_t max_depth_)
+    : _queue(),
+      _slots(max_depth_)
+  {
+  }
+
+  BoundedQueue(const BoundedQueue&) = delete;
+  BoundedQueue& operator=(const BoundedQueue&) = delete;
+  BoundedQueue(BoundedQueue&&) = delete;
+  BoundedQueue& operator=(BoundedQueue&&) = delete;
+
+  // -- Blocking enqueue (waits indefinitely for a slot) -------------------
+
+  template<typename U>
+  void
+  enqueue(U &&item_)
+  {
+    _slots.wait();
+    _queue.enqueue(std::forward<U>(item_));
+  }
+
+  template<typename U>
+  void
+  enqueue(PToken &ptok_, U &&item_)
+  {
+    _slots.wait();
+    _queue.enqueue(ptok_, std::forward<U>(item_));
+  }
+
+  // -- Non-blocking enqueue (fails immediately if full) -------------------
+
+  template<typename U>
+  bool
+  try_enqueue(U &&item_)
+  {
+    if(!_slots.tryWait())
+      return false;
+    _queue.enqueue(std::forward<U>(item_));
+    return true;
+  }
+
+  template<typename U>
+  bool
+  try_enqueue(PToken &ptok_, U &&item_)
+  {
+    if(!_slots.tryWait())
+      return false;
+    _queue.enqueue(ptok_, std::forward<U>(item_));
+    return true;
+  }
+
+  // -- Timed enqueue (waits up to timeout_usecs_ for a slot) --------------
+
+  template<typename U>
+  bool
+  try_enqueue_for(std::int64_t timeout_usecs_, U &&item_)
+  {
+    if(!_slots.wait(timeout_usecs_))
+      return false;
+    _queue.enqueue(std::forward<U>(item_));
+    return true;
+  }
+
+  template<typename U>
+  bool
+  try_enqueue_for(PToken &ptok_, std::int64_t timeout_usecs_, U &&item_)
+  {
+    if(!_slots.wait(timeout_usecs_))
+      return false;
+    _queue.enqueue(ptok_, std::forward<U>(item_));
+    return true;
+  }
+
+  // -- Unbounded enqueue (bypasses backpressure) --------------------------
+  // Used for internal control messages (e.g. thread exit signals) that
+  // must not be blocked by a full queue.
+
+  template<typename U>
+  void
+  enqueue_unbounded(U &&item_)
+  {
+    _queue.enqueue(std::forward<U>(item_));
+  }
+
+  // -- Blocking dequeue (signals a slot after consuming) ------------------
+
+  void
+  wait_dequeue(CToken &ctok_, T &item_)
+  {
+    _queue.wait_dequeue(ctok_, item_);
+    _slots.signal();
+  }
+
+  // -- Token creation -----------------------------------------------------
+
+  PToken
+  make_ptoken()
+  {
+    return PToken(_queue);
+  }
+
+  CToken
+  make_ctoken()
+  {
+    return CToken(_queue);
+  }
+};

vendored/libfuse/include/mutex.hpp

@@ -6,6 +6,8 @@
 #include "mutex_ndebug.hpp"
 #endif
 
+#include "scope_guard.hpp"
+
 typedef pthread_mutex_t mutex_t;
 
 // Simple mutex_t wrapper to provide RAII
@@ -50,3 +52,10 @@ public:
     mutex_unlock(_mutex);
   }
 };
+
+// Single-line mutex guard using scope_guard
+// Expands to mutex_lock() followed by DEFER mutex_unlock()
+// Both lock and unlock capture __FILE__/__func__/__LINE__ from the call site
+#define mutex_lockguard(m) \
+  mutex_lock(m);           \
+  DEFER { mutex_unlock(m); }

vendored/libfuse/include/thread_pool.hpp

@@ -1,41 +1,50 @@
+/*
+  ISC License
+
+  Copyright (c) 2026, Antonio SJ Musumeci <trapexit@spawn.link>
+
+  Permission to use, copy, modify, and/or distribute this software for any
+  purpose with or without fee is hereby granted, provided that the above
+  copyright notice and this permission notice appear in all copies.
+
+  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+
 #pragma once
 
-#include "moodycamel/blockingconcurrentqueue.h"
-#include "moodycamel/lightweightsemaphore.h"
+#include "bounded_queue.hpp"
 #include "invocable.h"
 
 #include "mutex.hpp"
 
 #include <algorithm>
 #include <atomic>
+#include <cerrno>
 #include <csignal>
+#include <cstdint>
 #include <cstring>
 #include <future>
 #include <memory>
+#include <optional>
 #include <stdexcept>
 #include <string>
 #include <thread>
-#include <vector>
 #include <utility>
+#include <vector>
 
 #include <pthread.h>
 #include <syslog.h>
 
-#define SEM
-//#undef SEM
-
-#ifdef SEM
-#define SEMA_WAIT(S) (S.wait())
-#define SEMA_SIGNAL(S) (S.signal())
-#else
-#define SEMA_WAIT(S)
-#define SEMA_SIGNAL(S)
-#endif
-
 
 struct ThreadPoolTraits : public moodycamel::ConcurrentQueueDefaultTraits
 {
-  static const int MAX_SEMA_SPINS = 1;
+  static const int MAX_SEMA_SPINS = 10;
 };
 
 
@@ -47,25 +56,29 @@ public:
 
 private:
   using Func  = ofats::any_invocable<void()>;
-  using Queue = moodycamel::BlockingConcurrentQueue<Func,ThreadPoolTraits>;
+  using Queue = BoundedQueue<Func,ThreadPoolTraits>;
+  struct ThreadExitSignal {};
 
 public:
   explicit
-  ThreadPool(const unsigned thread_count_    = std::thread::hardware_concurrency(),
-             const unsigned max_queue_depth_ = std::thread::hardware_concurrency(),
-             std::string const name_         = {});
+  ThreadPool(const unsigned thread_count_ = std::thread::hardware_concurrency(),
+             const unsigned max_queue_depth_ = std::thread::hardware_concurrency() * 2,
+             const std::string &name_ = {});
   ~ThreadPool();
 
+  ThreadPool(const ThreadPool&) = delete;
+  ThreadPool& operator=(const ThreadPool&) = delete;
+  ThreadPool(ThreadPool&&) = delete;
+  ThreadPool& operator=(ThreadPool&&) = delete;
+
 private:
   static void *start_routine(void *arg_);
 
 public:
-  int add_thread(std::string const name = {});
-  int remove_thread(void);
+  int add_thread(const std::string &name = {});
+  int remove_thread();
   int set_threads(const std::size_t count);
 
-  void shutdown(void);
-
 public:
   template<typename FuncType>
   void
@@ -76,6 +89,26 @@ public:
   void
   enqueue_work(FuncType &&func_);
 
+  template<typename FuncType>
+  bool
+  try_enqueue_work(ThreadPool::PToken &ptok_,
+                   FuncType &&func_);
+
+  template<typename FuncType>
+  bool
+  try_enqueue_work(FuncType &&func_);
+
+  template<typename FuncType>
+  bool
+  try_enqueue_work_for(ThreadPool::PToken  &ptok_,
+                       std::int64_t         timeout_usecs_,
+                       FuncType           &&func_);
+
+  template<typename FuncType>
+  bool
+  try_enqueue_work_for(std::int64_t  timeout_usecs_,
+                       FuncType    &&func_);
+
   template<typename FuncType>
   [[nodiscard]]
   std::future<std::invoke_result_t<FuncType>>
@@ -87,7 +120,6 @@ public:
 
 private:
   Queue _queue;
-  moodycamel::LightweightSemaphore _sema;
 
 private:
   std::string const      _name;
@@ -98,11 +130,10 @@ private:
 
 
 inline
-ThreadPool::ThreadPool(const unsigned    thread_count_,
-                       const unsigned    max_queue_depth_,
-                       const std::string name_)
-  : _queue(),
-    _sema(max_queue_depth_),
+ThreadPool::ThreadPool(const unsigned     thread_count_,
+                       const unsigned     max_queue_depth_,
+                       const std::string &name_)
+  : _queue(max_queue_depth_),
     _name(name_)
 {
   sigset_t oldset;
@@ -128,8 +159,11 @@ ThreadPool::ThreadPool(const unsigned    thread_count_,
           continue;
         }
 
-      if(!_name.empty())
-        pthread_setname_np(t,_name.c_str());
+      if(not _name.empty())
+        {
+          std::string name = _name.substr(0, 15);
+          pthread_setname_np(t, name.c_str());
+        }
 
       _threads.push_back(t);
     }
@@ -150,18 +184,25 @@ ThreadPool::ThreadPool(const unsigned    thread_count_,
 inline
 ThreadPool::~ThreadPool()
 {
+  std::vector<pthread_t> threads;
+
+  {
+    mutex_lockguard(_threads_mutex);
+    threads = _threads;
+  }
+
   syslog(LOG_DEBUG,
          "threadpool (%s): destroying %zu threads",
          _name.c_str(),
-         _threads.size());
+         threads.size());
 
-  for(auto t : _threads)
-    pthread_cancel(t);
-  for(auto t : _threads)
+  for(auto _ : threads)
+    _queue.enqueue_unbounded([](){ throw ThreadExitSignal{}; });
+  for(auto t : threads)
     pthread_join(t,NULL);
 }
 
-
+// Threads purposefully do not restore default signal handling.
 inline
 void*
 ThreadPool::start_routine(void *arg_)
@@ -171,8 +212,7 @@ ThreadPool::start_routine(void *arg_)
   bool done;
   ThreadPool::Func func;
   ThreadPool::Queue &q = btp->_queue;
-  moodycamel::LightweightSemaphore &sema = btp->_sema;
-  ThreadPool::CToken ctok(btp->_queue);
+  ThreadPool::CToken ctok(btp->_queue.make_ctoken());
 
   done = false;
   while(!done)
@@ -185,12 +225,26 @@ ThreadPool::start_routine(void *arg_)
         {
           func();
         }
-      catch(std::exception &e)
+      catch(const ThreadExitSignal&)
         {
           done = true;
         }
+      catch(std::exception &e)
+        {
+          syslog(LOG_CRIT,
+                 "threadpool (%s): uncaught exception caught by worker - %s",
+                 btp->_name.c_str(),
+                 e.what());
+        }
+      catch(...)
+        {
+          syslog(LOG_CRIT,
+                 "threadpool (%s): uncaught non-standard exception caught by worker",
+                 btp->_name.c_str());
+        }
 
-      SEMA_SIGNAL(sema);
+      // force destruction to release resources
+      func = {};
 
       pthread_setcancelstate(PTHREAD_CANCEL_ENABLE,NULL);
     }
@@ -198,11 +252,9 @@ ThreadPool::start_routine(void *arg_)
   return nullptr;
 }
 
-
-
 inline
 int
-ThreadPool::add_thread(const std::string name_)
+ThreadPool::add_thread(const std::string &name_)
 {
   int rv;
   pthread_t t;
@@ -227,120 +279,157 @@ ThreadPool::add_thread(const std::string name_)
       return -rv;
     }
 
-  if(!name.empty())
-    pthread_setname_np(t,name.c_str());
+  if(not name.empty())
+    {
+      std::string n = name.substr(0, 15);
+      pthread_setname_np(t,n.c_str());
+    }
 
   {
-    LockGuard lg(_threads_mutex);
-
+    mutex_lockguard(_threads_mutex);
     _threads.push_back(t);
   }
 
   return 0;
 }
 
-
 inline
 int
-ThreadPool::remove_thread(void)
+ThreadPool::remove_thread()
 {
   {
-    LockGuard lg(_threads_mutex);
-
+    mutex_lockguard(_threads_mutex);
     if(_threads.size() <= 1)
       return -EINVAL;
   }
 
-  std::promise<pthread_t> promise;
+  auto promise = std::make_shared<std::promise<std::optional<pthread_t>>>();
+
   auto func =
-    [this,&promise]()
+    [this,promise]()
     {
       pthread_t t;
 
       t = pthread_self();
-      promise.set_value(t);
 
       {
-        LockGuard lg(_threads_mutex);
+        mutex_lockguard(_threads_mutex);
 
-        for(auto i = _threads.begin(); i != _threads.end(); ++i)
+        if(_threads.size() <= 1)
           {
-            if(*i != t)
-              continue;
-
-            _threads.erase(i);
-            break;
+            promise->set_value(std::nullopt);
+            return;
           }
+
+        auto it = std::find(_threads.begin(),
+                            _threads.end(),
+                            t);
+        if(it != _threads.end())
+          _threads.erase(it);
       }
 
-      pthread_exit(NULL);
+      promise->set_value(t);
+
+      throw ThreadExitSignal{};
     };
 
-  enqueue_work(std::move(func));
-  pthread_join(promise.get_future().get(),NULL);
+  _queue.enqueue_unbounded(std::move(func));
 
-  return 0;
+  auto result = promise->get_future().get();
+  if(result.has_value())
+    {
+      pthread_join(result.value(),NULL);
+      return 0;
+    }
+
+  return -EINVAL;
 }
 
-
 inline
 int
-ThreadPool::set_threads(std::size_t const count_)
+ThreadPool::set_threads(const std::size_t count_)
 {
-  int diff;
+  if(count_ == 0)
+    return -EINVAL;
+
+  std::size_t current;
 
   {
-    LockGuard lg(_threads_mutex);
-
-    diff = ((int)count_ - (int)_threads.size());
+    mutex_lockguard(_threads_mutex);
+    current = _threads.size();
   }
 
-  for(auto i = diff; i > 0; --i)
+  for(std::size_t i = current; i < count_; ++i)
     add_thread();
-  for(auto i = diff; i < 0; ++i)
+  for(std::size_t i = count_; i < current; ++i)
     remove_thread();
 
-  return diff;
+  return 0;
 }
 
-
-inline
-void
-ThreadPool::shutdown(void)
-{
-  LockGuard lg(_threads_mutex);
-
-  for(pthread_t tid : _threads)
-    pthread_cancel(tid);
-  for(pthread_t tid : _threads)
-    pthread_join(tid,NULL);
-
-  _threads.clear();
-}
-
-
 template<typename FuncType>
 inline
 void
 ThreadPool::enqueue_work(ThreadPool::PToken  &ptok_,
                          FuncType           &&func_)
 {
-  SEMA_WAIT(_sema);
   _queue.enqueue(ptok_,
                  std::forward<FuncType>(func_));
 }
 
-
 template<typename FuncType>
 inline
 void
 ThreadPool::enqueue_work(FuncType &&func_)
 {
-  SEMA_WAIT(_sema);
   _queue.enqueue(std::forward<FuncType>(func_));
 }
 
 
+template<typename FuncType>
+inline
+bool
+ThreadPool::try_enqueue_work(ThreadPool::PToken &ptok_,
+                             FuncType &&func_)
+{
+  return _queue.try_enqueue(ptok_,
+                            std::forward<FuncType>(func_));
+}
+
+
+template<typename FuncType>
+inline
+bool
+ThreadPool::try_enqueue_work(FuncType &&func_)
+{
+  return _queue.try_enqueue(std::forward<FuncType>(func_));
+}
+
+
+template<typename FuncType>
+inline
+bool
+ThreadPool::try_enqueue_work_for(ThreadPool::PToken  &ptok_,
+                                 std::int64_t         timeout_usecs_,
+                                 FuncType           &&func_)
+{
+  return _queue.try_enqueue_for(ptok_,
+                                timeout_usecs_,
+                                std::forward<FuncType>(func_));
+}
+
+
+template<typename FuncType>
+inline
+bool
+ThreadPool::try_enqueue_work_for(std::int64_t  timeout_usecs_,
+                                 FuncType    &&func_)
+{
+  return _queue.try_enqueue_for(timeout_usecs_,
+                                std::forward<FuncType>(func_));
+}
+
+
 template<typename FuncType>
 [[nodiscard]]
 inline
@@ -359,8 +448,15 @@ ThreadPool::enqueue_task(FuncType&& func_)
     {
       try
         {
-          auto rv = func_();
-          promise_.set_value(std::move(rv));
+          if constexpr (std::is_void_v<TaskReturnType>)
+            {
+              func_();
+              promise_.set_value();
+            }
+          else
+            {
+              promise_.set_value(func_());
+            }
         }
       catch(...)
         {
@@ -368,7 +464,6 @@ ThreadPool::enqueue_task(FuncType&& func_)
         }
     };
 
-  SEMA_WAIT(_sema);
   _queue.enqueue(std::move(work));
 
   return future;
@@ -379,7 +474,7 @@ inline
 std::vector<pthread_t>
 ThreadPool::threads() const
 {
-  LockGuard lg(_threads_mutex);
+  mutex_lockguard(_threads_mutex);
 
   return _threads;
 }
@@ -389,5 +484,5 @@ inline
 ThreadPool::PToken
 ThreadPool::ptoken()
 {
-  return ThreadPool::PToken(_queue);
+  return _queue.make_ptoken();
 }