extended multiqueue to support blocking push

lib/include/srslte/common/multiqueue.h

@@ -51,69 +51,103 @@ class multiqueue_handler
     using std::queue<myobj>::size;
     using std::queue<myobj>::empty;
     using std::queue<myobj>::front;
+
+    std::condition_variable cv_full;
+    bool                    active = true;
   };
 
 public:
   explicit multiqueue_handler(uint32_t capacity_ = std::numeric_limits<uint32_t>::max()) : capacity(capacity_) {}
-  ~multiqueue_handler()
+  ~multiqueue_handler() { reset(); }
+
+  void reset()
   {
-    std::lock_guard<std::mutex> lck(mutex);
-    queues_active.clear();
-    queues.clear();
+    std::unique_lock<std::mutex> lock(mutex);
     running = false;
+    while (nof_threads_waiting > 0) {
+      uint32_t size = queues.size();
+      lock.unlock();
+      cv_empty.notify_one();
+      for (uint32_t i = 0; i < size; ++i) {
+        queues[i].cv_full.notify_all();
+      }
+      lock.lock();
+      // wait for all threads to unblock
+      cv_exit.wait(lock);
+    }
+    queues.clear();
   }
 
   int add_queue()
   {
-    uint32_t qidx = 0;
-    for (; qidx < queues_active.size() and queues_active[qidx]; ++qidx)
+    uint32_t                    qidx = 0;
+    std::lock_guard<std::mutex> lock(mutex);
+    if (not running) {
+      return -1;
+    }
+    for (; qidx < queues.size() and queues[qidx].active; ++qidx)
       ;
-    if (qidx == queues_active.size()) {
+    if (qidx == queues.size()) {
       // create new queue
-      std::lock_guard<std::mutex> lck(mutex);
-      queues_active.push_back(true);
       queues.emplace_back();
     } else {
-      queues_active[qidx] = true;
+      queues[qidx].active = true;
     }
     return (int)qidx;
   }
 
   int nof_queues()
   {
-    std::lock_guard<std::mutex> lck(mutex);
-    return std::count(queues_active.begin(), queues_active.end(), true);
+    std::lock_guard<std::mutex> lock(mutex);
+    uint32_t                    count = 0;
+    for (uint32_t i = 0; i < queues.size(); ++i) {
+      count += queues[i].active ? 1 : 0;
+    }
+    return count;
   }
 
-  bool try_push(int q_idx, const myobj& value)
+  template <typename FwdRef>
+  void push(int q_idx, FwdRef&& value)
   {
-    if (not running) {
-      return false;
+    {
+      std::unique_lock<std::mutex> lock(mutex);
+      while (is_queue_active_(q_idx) and queues[q_idx].size() >= capacity) {
+        nof_threads_waiting++;
+        queues[q_idx].cv_full.wait(lock);
+        nof_threads_waiting--;
+      }
+      if (not is_queue_active_(q_idx)) {
+        cv_exit.notify_one();
+        return;
+      }
+      queues[q_idx].push(std::forward<FwdRef>(value));
     }
+    cv_empty.notify_one();
+  }
+
+  bool try_push(int q_idx, const myobj& value)
+  {
     {
-      std::lock_guard<std::mutex> lck(mutex);
-      if (queues[q_idx].size() >= capacity) {
+      std::lock_guard<std::mutex> lock(mutex);
+      if (not is_queue_active_(q_idx) or queues[q_idx].size() >= capacity) {
         return false;
       }
       queues[q_idx].push(value);
     }
-    cv.notify_one();
+    cv_empty.notify_one();
     return true;
   }
 
   std::pair<bool, myobj> try_push(int q_idx, myobj&& value)
   {
-    if (not running) {
-      return {false, std::move(value)};
-    }
     {
       std::lock_guard<std::mutex> lck(mutex);
-      if (queues[q_idx].size() >= capacity) {
+      if (not is_queue_active_(q_idx) or queues[q_idx].size() >= capacity) {
         return {false, std::move(value)};
       }
       queues[q_idx].push(std::move(value));
     }
-    cv.notify_one();
+    cv_empty.notify_one();
     return {true, std::move(value)};
   }
 
@@ -121,19 +155,26 @@ public:
   {
     std::unique_lock<std::mutex> lock(mutex);
     while (running) {
-      cv.wait(lock);
       // Round-robin for all queues
-      for (uint32_t i = 0; queues.size(); ++i) {
+      for (const queue_wrapper& q : queues) {
         spin_idx = (spin_idx + 1) % queues.size();
-        if (queues_active[spin_idx] and not queues[spin_idx].empty()) {
+        if (is_queue_active_(spin_idx) and not queues[spin_idx].empty()) {
           if (value) {
             *value = std::move(queues[spin_idx].front());
           }
           queues[spin_idx].pop();
+          if (nof_threads_waiting > 0) {
+            lock.unlock();
+            queues[spin_idx].cv_full.notify_one();
+          }
           return spin_idx;
         }
       }
+      nof_threads_waiting++;
+      cv_empty.wait(lock);
+      nof_threads_waiting--;
     }
+    cv_exit.notify_one();
     return -1;
   }
 
@@ -152,14 +193,14 @@ public:
   const myobj& front(int qidx)
   {
     std::lock_guard<std::mutex> lck(mutex);
-    return queues.front();
+    return queues[qidx].front();
   }
 
   void erase_queue(int qidx)
   {
     std::lock_guard<std::mutex> lck(mutex);
-    if (queues_active[qidx]) {
-      queues_active[qidx] = false;
+    if (is_queue_active_(qidx)) {
+      queues[qidx].active = false;
       while (not queues[qidx].empty()) {
         queues[qidx].pop();
       }
@@ -169,17 +210,19 @@ public:
   bool is_queue_active(int qidx)
   {
     std::lock_guard<std::mutex> lck(mutex);
-    return queues_active[qidx];
+    return is_queue_active_(qidx);
   }
 
 private:
+  bool is_queue_active_(int qidx) const { return running and queues[qidx].active; }
+
   std::mutex                 mutex;
-  std::condition_variable    cv;
+  std::condition_variable    cv_empty, cv_exit;
   uint32_t                   spin_idx = 0;
   bool                       running  = true;
-  std::vector<bool>          queues_active;
   std::vector<queue_wrapper> queues;
   uint32_t                   capacity;
+  uint32_t                   nof_threads_waiting = 0;
 };
 
 } // namespace srslte

lib/test/common/queue_test.cc

@@ -21,6 +21,8 @@
 
 #include <iostream>
 #include <srslte/common/multiqueue.h>
+#include <thread>
+#include <unistd.h>
 
 #define TESTASSERT(cond)                                                                                               \
   {                                                                                                                    \
@@ -98,7 +100,117 @@ int test_multiqueue()
   return 0;
 }
 
+int test_multiqueue_threading()
+{
+  std::cout << "\n===== TEST multiqueue threading test: start =====\n";
+
+  int                     capacity = 4, number, start_number = 2, nof_pushes = capacity + 1;
+  multiqueue_handler<int> multiqueue(capacity);
+  int                     qid1 = multiqueue.add_queue();
+  auto push_blocking_func      = [&multiqueue](int qid, int start_value, int nof_pushes, bool* is_running) {
+    for (int i = 0; i < nof_pushes; ++i) {
+      multiqueue.push(qid, start_value + i);
+      std::cout << "t1: pushed item " << i << std::endl;
+    }
+    std::cout << "t1: pushed all items\n";
+    *is_running = false;
+  };
+
+  bool        t1_running = true;
+  std::thread t1(push_blocking_func, qid1, start_number, nof_pushes, &t1_running);
+
+  TESTASSERT(t1_running)
+  usleep(1000);
+  TESTASSERT((int)multiqueue.size(qid1) == capacity)
+
+  for (int i = 0; i < nof_pushes; ++i) {
+    TESTASSERT(multiqueue.wait_pop(&number) == qid1)
+    TESTASSERT(number == start_number + i)
+    std::cout << "main: popped item " << i << "\n";
+  }
+  std::cout << "main: popped all items\n";
+  usleep(1000);
+  TESTASSERT(not t1_running)
+  TESTASSERT(multiqueue.size(qid1) == 0)
+
+  multiqueue.reset();
+  t1.join();
+
+  std::cout << "outcome: Success\n";
+  std::cout << "==================================================\n";
+
+  return 0;
+}
+
+int test_multiqueue_threading2()
+{
+  std::cout << "\n===== TEST multiqueue threading test 2: start =====\n";
+  // Description: push items until blocking in thread t1. Unblocks in main thread by calling multiqueue.reset()
+
+  int                     capacity = 4, start_number = 2, nof_pushes = capacity + 1;
+  multiqueue_handler<int> multiqueue(capacity);
+  int                     qid1 = multiqueue.add_queue();
+  auto push_blocking_func      = [&multiqueue](int qid, int start_value, int nof_pushes, bool* is_running) {
+    for (int i = 0; i < nof_pushes; ++i) {
+      multiqueue.push(qid, start_value + i);
+    }
+    std::cout << "t1: pushed all items\n";
+    *is_running = false;
+  };
+
+  bool        t1_running = true;
+  std::thread t1(push_blocking_func, qid1, start_number, nof_pushes, &t1_running);
+
+  TESTASSERT(t1_running)
+  usleep(1000);
+  TESTASSERT((int)multiqueue.size(qid1) == capacity)
+
+  multiqueue.reset();
+  t1.join();
+
+  std::cout << "outcome: Success\n";
+  std::cout << "===================================================\n";
+
+  return 0;
+}
+
+int test_multiqueue_threading3()
+{
+  std::cout << "\n===== TEST multiqueue threading test 3: start =====\n";
+  // pop will block in a separate thread, but multiqueue.reset() will unlock it
+
+  int                     capacity = 4;
+  multiqueue_handler<int> multiqueue(capacity);
+  int                     qid1              = multiqueue.add_queue();
+  auto                    pop_blocking_func = [&multiqueue](int qid, bool* success) {
+    int number;
+    int id   = multiqueue.wait_pop(&number);
+    *success = id < 0;
+  };
+
+  bool        t1_success = false;
+  std::thread t1(pop_blocking_func, qid1, &t1_success);
+
+  TESTASSERT(not t1_success)
+  usleep(1000);
+  TESTASSERT(not t1_success)
+  TESTASSERT((int)multiqueue.size(qid1) == 0)
+
+  // Should be able to unlock all
+  multiqueue.reset();
+  t1.join();
+  TESTASSERT(t1_success)
+
+  std::cout << "outcome: Success\n";
+  std::cout << "===================================================\n";
+
+  return 0;
+}
+
 int main()
 {
   TESTASSERT(test_multiqueue() == 0);
+  TESTASSERT(test_multiqueue_threading() == 0);
+  TESTASSERT(test_multiqueue_threading2() == 0);
+  TESTASSERT(test_multiqueue_threading3() == 0);
 }