Only send one byte and ignore any following calls to poke.

src/torrent/utils/thread_interrupt.cc

@@ -45,8 +45,14 @@
 
 namespace torrent {
 
+thread_interrupt::thread_interrupt(int fd) :
+  m_poking(false) {
+  m_fileDesc = fd;
+  get_fd().set_nonblock();
+}
+
 thread_interrupt::~thread_interrupt() {
-  if (m_fileDesc != -1)
+  if (m_fileDesc == -1)
     return;
 
   ::close(m_fileDesc);
@@ -55,6 +61,11 @@ thread_interrupt::~thread_interrupt() {
 
 bool
 thread_interrupt::poke() {
+  if (is_poking())
+    return true;
+
+  __sync_bool_compare_and_swap(&m_other->m_poking, false, true);
+
   int result = ::send(m_fileDesc, "a", 1, 0);
 
   if (result == 0 ||
@@ -66,17 +77,16 @@ thread_interrupt::poke() {
 
 thread_interrupt::pair_type
 thread_interrupt::create_pair() {
-  int fd1;
-  int fd2;
+  int fd1, fd2;
 
   if (!SocketFd::open_socket_pair(fd1, fd2))
     throw internal_error("Could not create socket pair for thread_interrupt: " + std::string(rak::error_number::current().c_str()) + ".");
 
   thread_interrupt* t1 = new thread_interrupt(fd1);
   thread_interrupt* t2 = new thread_interrupt(fd2);
 
-  t1->get_fd().set_nonblock();
-  t2->get_fd().set_nonblock();
+  t1->m_other = t2;
+  t2->m_other = t1;
 
   return pair_type(t1, t2);
 }
@@ -89,6 +99,8 @@ thread_interrupt::event_read() {
   if (result == 0 ||
       (result == -1 && !rak::error_number::current().is_blocked_momentary()))
     throw internal_error("Invalid result reading from thread_interrupt socket.");
+
+  __sync_bool_compare_and_swap(&m_poking, true, false);
 }
 
 }

src/torrent/utils/thread_interrupt.h

@@ -52,18 +52,29 @@ class LIBTORRENT_EXPORT lt_cacheline_aligned thread_interrupt : public Event {
 
   static pair_type    create_pair();
 
+  bool                is_poking() const;
+
   bool                poke();
 
   void                event_read();
   void                event_write() {}
   void                event_error() {}
 
 private:
+  thread_interrupt(int fd);
+
   SocketFd&           get_fd() { return *reinterpret_cast<SocketFd*>(&m_fileDesc); }
 
-  thread_interrupt(int fd) { m_fileDesc = fd; }
+  thread_interrupt*   m_other;
+  bool                m_poking lt_cacheline_aligned;
 };
 
+inline bool
+thread_interrupt::is_poking() const {
+  __sync_synchronize();
+  return m_poking;
+}
+
 }
 
 #endif