CMakeLists.txt

@@ -187,6 +187,7 @@ set( fc_sources
      src/interprocess/signals.cpp
      src/interprocess/file_mapping.cpp
      src/interprocess/mmap_struct.cpp
+     src/interprocess/file_mutex.cpp
      src/rpc/cli.cpp
      src/rpc/http_api.cpp
      src/rpc/json_connection.cpp
@@ -374,6 +375,9 @@ add_definitions(-DBOOST_TEST_DYN_LINK)
 ENDIF(MSVC)
 ENDIF()
 
+add_executable( bip_lock tests/bip_lock.cpp )
+target_link_libraries( bip_lock fc )
+
 add_executable( api tests/api.cpp )
 target_link_libraries( api fc )
 

include/fc/interprocess/file_mutex.hpp

@@ -0,0 +1,42 @@
+#pragma once
+#include <fc/time.hpp>
+#include <fc/thread/spin_yield_lock.hpp>
+
+namespace fc { 
+  class microseconds;
+  class time_point;
+  class path;
+  struct context;
+
+  namespace detail { class file_mutex_impl; }
+
+  /**
+   *  The purpose of this class is to support synchronization of 
+   *  processes, threads, and coop-threads.  
+   *
+   *  Before grabbing the lock for a thread or coop, a file_mutex will first
+   *  grab a process-level lock.  After grabbing the process level lock, it will
+   *  synchronize in the same way as a local process lock.
+   */
+  class file_mutex {
+     public:
+        file_mutex( const fc::path& filename );
+        ~file_mutex();
+
+        bool try_lock();
+        bool try_lock_for( const microseconds& rel_time );
+        bool try_lock_until( const time_point& abs_time );
+        void lock();
+        void unlock();
+
+        void lock_shared();
+        void unlock_shared();
+        bool try_lock_shared();
+
+        int  readers()const;
+
+     private:
+        std::unique_ptr<detail::file_mutex_impl> my;
+  };
+
+} // namespace fc

src/interprocess/file_mutex.cpp

@@ -0,0 +1,100 @@
+#include <fc/interprocess/file_mutex.hpp>
+//#include <fc/thread/mutex.hpp>
+#include <fc/thread/mutex.hpp>
+#include <fc/filesystem.hpp>
+#include <boost/interprocess/sync/file_lock.hpp>
+#include <boost/interprocess/sync/scoped_lock.hpp>
+#include <boost/atomic.hpp>
+
+#include <fc/thread/thread.hpp>
+#include <fc/log/logger.hpp>
+
+namespace fc {
+  namespace bip = boost::interprocess;
+
+  void yield();
+
+  namespace detail { 
+     class file_mutex_impl  {
+        public:
+          file_mutex_impl( const char* f )
+          :_file_mutex( f ),_reader_count(0){}
+
+          fc::mutex  _write_lock;
+          bip::file_lock       _file_mutex;
+          boost::atomic<int>   _reader_count;
+     };
+  }
+
+  file_mutex::file_mutex( const fc::path& file )
+  {
+     my.reset( new detail::file_mutex_impl( file.generic_string().c_str() ) );
+  }
+
+  file_mutex::~file_mutex() {
+  }
+
+  int  file_mutex::readers()const {
+    return my->_reader_count.load();
+  }
+
+  bool file_mutex::try_lock() {
+     return false;
+     if( my->_write_lock.try_lock() ) {
+        if( my->_file_mutex.try_lock() )
+           return true;
+     }
+     if( my->_file_mutex.try_lock() ) {
+        if( my->_write_lock.try_lock() ) {
+          return true;
+        } else {
+          my->_file_mutex.unlock();
+        }
+     }
+     return false;
+  }
+
+  bool file_mutex::try_lock_for( const microseconds& rel_time ) {
+     return false;
+  }
+
+  bool file_mutex::try_lock_until( const time_point& abs_time ) {
+     return false;
+  }
+
+  void file_mutex::lock() {
+     my->_write_lock.lock();
+     while( my->_reader_count.load() > 0 ) {
+        fc::usleep( fc::microseconds(10) );
+     }
+     my->_file_mutex.lock();
+  }
+
+  void file_mutex::unlock() {
+     my->_file_mutex.unlock();
+     my->_write_lock.unlock();
+  }
+
+  void file_mutex::lock_shared() {
+    bip::scoped_lock< fc::mutex > lock( my->_write_lock );
+    if( 0 == my->_reader_count.fetch_add( 1, boost::memory_order_relaxed ) )
+       my->_file_mutex.lock_sharable();
+  }
+
+  void file_mutex::unlock_shared() {
+    if( 1 == my->_reader_count.fetch_add( -1, boost::memory_order_relaxed ) )
+       my->_file_mutex.unlock_sharable();
+  }
+
+  bool file_mutex::try_lock_shared() {
+    return false;
+    if( my->_write_lock.try_lock() ) {
+       if( my->_reader_count.load() == 0 && my->_file_mutex.try_lock_sharable() ) {
+          my->_reader_count++;
+       }
+       my->_write_lock.unlock();
+    }
+    return false;
+  }
+
+} // namespace fc 

tests/bip_lock.cpp

@@ -0,0 +1,44 @@
+#include <iostream>
+#include <fc/interprocess/file_mutex.hpp>
+#include <fc/filesystem.hpp>
+#include <fc/log/logger.hpp>
+#include <fc/thread/thread.hpp>
+
+int main( int argc, char** argv ) {
+   if( argc < 2 ) return 0;
+   fc::file_mutex m( argv[1] );
+   auto mptr = &m;
+
+   fc::thread in("in");
+
+  std::string cmd;
+  std::cout << ">>> ";
+  std::cin >> cmd;
+  int i = 0;
+  while( !std::cin.eof() && cmd != "q" ) {
+    ++i;
+    fc::async( [i, cmd,mptr]() {
+       ilog( "start ${c} ${i}", ("c",cmd)("i",i) );
+       if( cmd == "L" ) {
+          mptr->lock();
+       } else if( cmd == "l" ) {
+          mptr->lock_shared();
+       } else if( cmd == "U" ) {
+          mptr->unlock();
+       } else if( cmd == "u" ) {
+          mptr->unlock_shared();
+       }
+       ilog( "end ${c} ${i}", ("c",cmd)("i",i) );
+    } );
+    fc::usleep( fc::microseconds( 1000 ) );
+    cmd = in.async( [&]() {
+       std::string tmp;
+       wdump((m.readers()));
+       std::cin >> tmp;
+       return tmp;
+    } );
+  }
+  std::cout << "done";
+
+  return 0;
+}