locking

I have a class which can be created by multiple threads. But at one function the code needs to be protected, so I decided to use the boost interprocess mutex. Every class creates or opens the same Mutex in it's constructor: MyClass::MyClass() { boost::interprocess::named_mutex m_Lock( boost::interprocess::open_or_create, "myLock" ); } So now there comes the point where the critical code part is called: int MyClass::MyFunction() { boost::interprocess::scoped_lock<boost::interprocess::named_mutex> lock( m_Lock, boost::interprocess::try_to_lock); if(!lock) { return -1; } // else do some stuff

(question revised): So far, the answers all include a single thread re-entering the lock region linearly, through things like recursion, where you can trace the steps of a single thread entering the lock twice. But is it possible somehow, for a single thread (perhaps from the ThreadPool, perhaps as a result of timer events or async events or a thread going to sleep and being awaken/reused in some other chunk of code separately) to somehow be spawned in two different places independently of each other, and hence, run into the lock re-entrance problem when the developer didn't expect it by

I tried using temp files: char *temp = tempnam(NULL, "myapp_"); printf("Tempname: %s", temp) // Prints /tmp/myapp_random while (1) { } But when I check /tmp (while the app is still running), the myapp_random is not there! As for using File Locks, I can't get a good grasp on it, I tried looking at <fcntl.h> but it seems to focus on locks in specified portions of a file. I just want to use the file entirely as a lock (which is why I prefer trying the temp file approach). Any ideas? tempnam doesn't create the file, it just gives you a filename that didn't exist at the time you called it. You

We have an issue with some deadlock and I posted this question . With some help and a lot of searching myself I believe I figured out what is going on. In order to solve the deadlocks without controlling lock escalation I need to understand why sql server locks the whole table on inserting one row. Here is my insert statement (with renamed variables): DECLARE @Type1 INT = 11, @Type2 INT = NULL, @Value1 VARCHAR(20) = '0', @Value2 VARCHAR(20) = '0', @Value3 VARCHAR(20) = '0', @Value4 VARCHAR(20) = '0', @Date1 DATETIME = '2011-11-25', @Date2 DATETIME = '2011-11-25', @Value5 NVARCHAR(50) = '',

I have some functions that interactively load python modules using __import__ I recently stumbled upon some article about an "import lock" in Python, that is, a lock specifically for imports (not just the GIL). But the article was old so maybe that's not true anymore. This makes me wonder about the practice of importing in a thread. Are import / __import__ thread safe? Can they create dead locks? Can they cause performance issues in a threaded application? EDIT 12 Sept 2012 Thanks for the great reply Soravux. So import are thread safe, and I'm not worrying about deadlocks, since the functions

I have several threads (some of which are spawned by Process X, others by Process Y, et cetera ), and each thread needs to write to a file MyFile . However, if Thread T1 starts writing to MyFile first, then, when Thread T2 starts writing, it needs to wait for T1 to release the file , so that it can read the contents that were written in Thread T1 . In other words, each thread would have a finalizeThread method, like so: private void finalizeThread() { File f = new File("MyFile.dat"); f.createNewFile(); // atomically creates the file, if it doesn't exist locked_section { readContentsFromFile(f)

What are the API calls to copy a file that is currently locked. I'm hoping to be able to use .Net, but Win32 calls would be fine as well. Please feel free to chime in about the same functionality on Unix, or any other OS. You can use the VSS (Volume Shadow Copy Service, not Visual SourceSafe) API for this purpose. While powerful, this isn't exactly an easy-to-use API: the Overview of Processing a Backup Under VSS should give you an idea what's involved. Even though it's a relatively recent API, .NET support for VSS is pretty much (and inexcusably) nonexistent. You can't call most of the API