The main difference is that a Lock can only be acquired once. It cannot be acquired again, until it is released. (After it’s been released, it can be re-acaquired by any thread). An RLock on the other hand, can be acquired multiple times, by the same thread. It needs to be released the same number … Read more
The snippet synchronized(X.class) uses the class instance as a monitor. As there is only one class instance (the object representing the class metadata at runtime) one thread can be in this block. With synchronized(this) the block is guarded by the instance. For every instance only one thread may enter the block. synchronized(X.class) is used to … Read more
Try adding <lockingModel type=”log4net.Appender.FileAppender+MinimalLock” /> to your <appender /> element. There is some performance impact because this means that log4net will lock the file, write to it, and unlock it for each write operation (as opposed to the default behavior, which acquires and holds onto the lock for a long time). One implication of the … Read more
Here is an article that goes into the cost. Short answer is 50ns.
No, not as long as you are locking on the same object. The recursive code effectively already has the lock and so can continue unhindered. lock(object) {…} is shorthand for using the Monitor class. As Marc points out, Monitor allows re-entrancy, so repeated attempts to lock on an object on which the current thread already … Read more
Re-entrant locking A reentrant lock is one where a process can claim the lock multiple times without blocking on itself. It’s useful in situations where it’s not easy to keep track of whether you’ve already grabbed a lock. If a lock is non re-entrant you could grab the lock, then block when you go to … Read more
It isn’t “very common to use a private static readonly object for locking in multi threading” – rather, it is common to use a lock at the appropriate / chosen granularity. Sometimes that is static. More often, IMO, it isn’t – but is instance based. The main time you see a static lock is for … Read more
Locking tables prevents other DB users from affecting the rows/tables you’ve locked. But locks, in and of themselves, will NOT ensure that your logic comes out in a consistent state. Think of a banking system. When you pay a bill online, there’s at least two accounts affected by the transaction: Your account, from which the … Read more
Use this: Objective-C: [[UIApplication sharedApplication] setIdleTimerDisabled: YES]; Swift (legacy): UIApplication.sharedApplication().idleTimerDisabled = true Swift 3 and above: UIApplication.shared.isIdleTimerDisabled = true Make sure to import UIKit. Here is the link to the documentation from developer.apple.com.
Since 9.6 this is a lot easier as it introduced the function pg_blocking_pids() to find the sessions that are blocking another session. So you can use something like this: select pid, usename, pg_blocking_pids(pid) as blocked_by, query as blocked_query from pg_stat_activity where cardinality(pg_blocking_pids(pid)) > 0;