shared-memory

Possible Duplicate: Thread safety in Java class I'm reading Java concurrency in Practice , and I've come to an example that puzzles me. The authors state that this class is not threadsafe public class MutableInteger { private int number; public int getInt() { return number; } public void setInt(int val) { number = val; } } And they also state that synchronizing only one method (the setter for example) would not do; you have to syncronize both. My question is: Why? Wouldn't synchronizing the setter just do? Java has a happens before/happens after memory model. There needs to be some common

I'm trying to connect to a local database (SQL Server 2008) from Java. I have disabled the tcp connections per customer requirements and I can't connect. I have to disable too the service SQL Server Browser. I write the next statement in Java: conexion = DriverManager.getConnection("jdbc:sqlserver://localhost\\SQLEXPRESS;user=user;password=password"); and I have the following error: "java.net.SocketTimeoutException: Receive timed out". (then it tells me that probably there is a firewall and that I should run the SQL Server Browser). If I try to connect from the Microsoft SQL Server Managment

After thinking about the the whole concept of shared memory , a question came up: can two processes share the same shared memory segment ? can two threads share the same shared memory ? After thinking about it a little more clearly , I'm almost positive that two processes can share the same shared memory segment , where the first is the father and the second is the son , that was created with a fork() , but what about two threads ? Thanks can two processes share the same shared memory segment? Yes and no. Typically with modern operating systems, when another process is forked from the first,

How do I prevent the GC from provoking copy-on-write, when I fork my process ? I have recently been analyzing the garbage collector's behavior in Ruby, due to some memory issues that I encountered in my program (I run out of memory on my 60core 0.5Tb machine even for fairly small tasks). For me this really limits the usefulness of ruby for running programs on multicore servers. I would like to present my experiments and results here. The issue arises when the garbage collector runs during forking. I have investigated three cases that illustrate the issue. Case 1: We allocate a lot of objects

I have a shared memory used by multiple processes, these processes are created using MPI . Now I need a mechanism to control the access of this shared memory. I know that named semaphore and flock mechanisms can be used to do this but just wanted to know if MPI provides any special locking mechanism for shared memory usage ? I am working on C under Linux. MPI actually does provide support for shared memory now (as of version 3.0). You might try looking at the One-sided communication chapter ( http://www.mpi-forum.org/docs/mpi-3.0/mpi30-report.pdf ) starting with MPI_WIN_ALLOCATE_SHARED (11.2.3

Does the POSIX standard allow a named shared memory block to contain a mutex and condition variable? We've been trying to use a mutex and condition variable to synchronise access to named shared memory by two processes on a LynuxWorks LynxOS-SE system (POSIX-conformant). One shared memory block is called "/sync" and contains the mutex and condition variable, the other is "/data" and contains the actual data we are syncing access to. We're seeing failures from pthread_cond_signal() if both processes don't perform the mmap() calls in exactly the same order , or if one process mmaps in some other

I'm using boost::interprocess::vector to share some strings between processes, and I want to make sure I do not overflow the shared memory segment it lives in. How do I find how much space the vector takes in memory, and how much memory a special segment-allocated string will take? typedef boost::interprocess::managed_shared_memory::segment_manager SegmentManager; typedef boost::interprocess::allocator<char, SegmentManager> CharAllocator; typedef boost::interprocess::basic_string<char, std::char_traits<char>, CharAllocator> ShmString; typedef boost::interprocess::allocator<ShmString,