locking

How often do you find yourself actually using spinlocks in your code? How common is it to come across a situation where using a busy loop actually outperforms the usage of locks? Personally, when I write some sort of code that requires thread safety, I tend to benchmark it with different synchronization primitives, and as far as it goes, it seems like using locks gives better performance than using spinlocks. No matter for how little time I actually hold the lock, the amount of contention I receive when using spinlocks is far greater than the amount I get from using locks (of course, I run my

From the docs : threading.RLock() -- A factory function that returns a new reentrant lock object. A reentrant lock must be released by the thread that acquired it. Once a thread has acquired a reentrant lock, the same thread may acquire it again without blocking; the thread must release it once for each time it has acquired it. I am not sure why do we need this? what's the difference between Rlock and Lock ? 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

Reading through the Python docs I came across RLock . Can someone explain to me (with example) a scenario in which RLock would be preferred to Lock ? With particular reference to: RLock 's “recursion level”. How is this useful? A threads "ownership" of an RLock object Performance? User This is one example where I see the use: Useful when you want to have thread-safe access from outside the class and use the same methods from inside the class: class X: def __init__(self): self.a = 1 self.b = 2 self.lock = threading.RLock() def changeA(self): with self.lock: self.a = self.a + 1 def changeB(self)

How can I prevent screen lock only when using Navigation. Waze has the option to do that, how can I do this in my App? atwalsh Use this: Objective-C: [[UIApplication sharedApplication] setIdleTimerDisabled: YES]; Swift (legacy): UIApplication.sharedApplication().idleTimerDisabled = true Swift 3/4: UIApplication.shared.isIdleTimerDisabled = true Make sure to import UIKit . Here is the link to the documentation from apple.developer.com. For Swift 3.0 here are two options depending on where you want to invoke the code: Inside AppDelegate.swift: application.idleTimerDisabled = true Outside

What's the best way to implement a Hash that can be modified across multiple threads, but with the smallest number of locks. For the purposes of this question, you can assume that the Hash will be read-heavy. It must be thread-safe in all Ruby implementations, including ones that operate in a truly simultaneous fashion, such as JRuby, and it must be written in pure-Ruby (no C or Java allowed). Feel free to submit a naïve solution that always locks, but that isn't likely to be the best solution. Points for elegance, but a smaller likelihood of locking wins over smaller code. ara t howard Okay,