A good resource for understanding why volatile is needed comes from the JCIP book. Wikipedia has a decent explanation of that material as well. The real problem is that Thread A may assign a memory space for instance before it is finished constructing instance. Thread B will see that assignment and try to use it. … Read more
I wouldn’t be suprised if it was someone who saw this: private readonly object lockObj = new object(); private void MyMethod() { lock(lockObj) { // do amazing stuff, so amazing it can only run once at a time // e.g. comands on the Mars Rover, or programs on iOS pre 4 / 5 ?? } … Read more
Linux has a reference-count mechanism, so you can delete the file while it is executing, and it will continue to exist as long as some process (Which previously opened it) has an open handle for it. The directory entry for the file is removed when you delete it, so it cannot be opened any more, … Read more
In general, for any thread safety problem you will need to protect your internal data structures with locks. This can be done with various levels of granularity. You can use fine-grained locking, where every separate structure has its own lock. You can use coarse-grained locking where one lock protects everything (the GIL approach). There are … Read more
Yes. Reads and writes of the following data types are atomic: bool, char, byte, sbyte, short, ushort, uint, int, float, and reference types. as found in C# Language Spec. Edit: It’s probably also worthwhile understanding the volatile keyword.
I note that no one has mentioned in their answers to this old question that releasing a lock upon an exception is an incredibly dangerous thing to do. Yes, lock statements in C# have “finally” semantics; when control exits the lock normally or abnormally, the lock is released. You’re all talking about this like it … Read more
You can use a concurrent collection. The System.Collections.Concurrent namespace provides several thread-safe collection classes that should be used in place of the corresponding types in the System.Collections and System.Collections.Generic namespaces whenever multiple threads are accessing the collection concurrently. You could for example use ConcurrentBag since you have no guarantee which order the items will be … Read more
Why would UPDLOCK block selects? The Lock Compatibility Matrix clearly shows N for the S/U and U/S contention, as in No Conflict. As for the HOLDLOCK hint the documentation states: HOLDLOCK: Is equivalent to SERIALIZABLE. For more information, see SERIALIZABLE later in this topic. … SERIALIZABLE: … The scan is performed with the same semantics … Read more
Lock is a questionable idea in JS which is intended to be threadless and not needing concurrency protection. You’re looking to combine calls on deferred execution. The pattern I follow for this is the use of callbacks. Something like this: var functionLock = false; var functionCallbacks = []; var lockingFunction = function (callback) { if … Read more