fcntl() is the one API to choose, since it is the least broken and is POSIX. It is the only one that works across NFS. That said it is a complete disaster, too, since locks are bound to processes, not file descriptors. That means that if you lock a file and then some other thread … Read more
When you use the Image.FromFile(strFileName) method to create the Image, the method locks the file until you release the Image. The exact reason is explained below. And it’s why you can’t access more than one time to the same image file with this method. You could instead: use the Image.FromStream(stream) method. that you use with … Read more
Yes, the ACTION_USER_PRESENT is broadcasted after the user unlocks: http://developer.android.com/reference/android/content/Intent.html#ACTION_USER_PRESENT Note that this is a protected broadcast and if the user is using a lock screen replacement such as WidgetLocker or NoLock the USER_PRESENT may not be sent or may be sent at the wrong time. For detecting WidgetLocker‘s unlock see: http://teslacoilsw.com/widgetlocker/developers
Yes, there is indeed a race condition in the sample script. You can use bash’s noclobber option in order to get a failure in case of a race, when a different script sneaks in between the -f test and the touch. The following is a sample code-snippet (inspired by this article) that illustrates the mechanism: … Read more
The best guide for locking and threading I found, is this page (this is the text I consult when working with locking and threading): http://www.albahari.com/threading/ You want the paragraph “Locking and Thread Safety”, but read the rest as well, it is very well written.
I like doing it like this public class Synchronizer { private Dictionary<int, object> locks; private object myLock; public Synchronizer() { locks = new Dictionary<int, object>(); myLock = new object(); } public object this[int index] { get { lock (myLock) { object result; if (locks.TryGetValue(index, out result)) return result; result = new object(); locks[index] = result; … Read more
As Dani has already mentioned in the comment: It’s a bug in Windows 7 and likely in Windows Server 2008 (possibly 64bit versions only). It surfaces when you disable Application Experience service. Re-enabling this service has fixed this problem for me. A bit more info here as to why it’s causing a problem. List of … Read more
Let me go through your cases and explain how these locks work: 1 case T1 wants to update some rows in your test table. This transaction puts IX lock on all table and X lock on the first 5 rows. T2 wants to update some rows in your test table. This transaction puts IX (because … Read more
I like to beat dead horses! 🙂 The “lightest” way to increment the count from multiple threads is: Interlocked.Increment(ref count); But as others have pointed out: if you’re doing it inside Parallel.ForEach then you’re probably doing something wrong. I’m suspecting that for some reason you’re using ForEach but you need an index to the item … Read more
EDIT: as @Bonshington commented, this answer refers to NSCondition (as opposed to NSConditionLock): – (void) method1 { [myCondition lock]; while (!someCheckIsTrue) [myCondition wait]; // Do something. [myCondition unlock]; } – (void) method2 { [myCondition lock]; // Do something. someCheckIsTrue = YES; [myCondition signal]; [myCondition unlock]; } The someCheckIsTrue can be anything, it could be a … Read more