Guava has something like this being released in 13.0; you can get it out of HEAD if you like. Striped<Lock> more or less allocates a specific number of locks, and then assigns strings to locks based on their hash code. The API looks more or less like Striped<Lock> locks = Striped.lock(stripes); Lock l = locks.get(string); … Read more
You can use Darwin notifications, to listen for the events. From my testing on a jailbroken iOS 5.0.1 iPhone 4, I think that one of these events might be what you need: com.apple.springboard.lockstate com.apple.springboard.lockcomplete Note: according to the poster’s comments to a similar question I answered here, this should work on a non-jailbroken phone, too. … Read more
I know this question is a bit older, but I just had the same issue and wanted to share my learnings. I wasn’t quite satisfied with st0nes answer, since (at least for postgres) a LOCK TABLE statement can only be issued within a transaction. And although in Django usually almost everything happens within a transaction, … Read more
from the (pre-edit) link Slower than page-level or table-level locks when used on a large part of the table because you must acquire many more locks use a row level lock if you are only hitting a row or two. If your code hits many or unknown rows, stick with table lock.
You can lock tables using the MySQL LOCK TABLES command like this: LOCK TABLES tablename WRITE; # Do other queries here UNLOCK TABLES; See: http://dev.mysql.com/doc/refman/5.5/en/lock-tables.html
Take a look at the enlightening presentation File Locking Tricks and Traps: This short talk presents several common pitfalls of file locking and a few useful tricks for using file locking more effectively. Edit: To address your questions more precisely: Is there a better synchronization method than the lock file? As @Hasturkun already mentioned and … Read more
Normally when you look into optimistic locking you also use a library like Hibernate or an other JPA-Implementation with @Version support. Example could read like this: public class Person { private String firstName; private String lastName; private int age; private Color favoriteColor; @Version private Long version; } while obviously there is no point of adding … Read more
According to MSDN, SemaphoreSlim.WaitAsync may throw: ObjectDisposedException – If the semaphore has been disposed ArgumentOutOfRangeException – if you choose the overload which accepts an int and it is a negative number (excluding -1) In both cases, the SemaphoreSlim wont acquire the lock, which makes it unnessacery to release it in a finally block. One thing … Read more
As the other answerer noted, the original code is removing the SemaphoreSlim from the ConcurrentDictionary before it releases the semaphore. So, you’ve got too much semaphore churn going on – they’re being removed from the dictionary when they could still be in use (not acquired, but already retrieved from the dictionary). The problem with this … Read more
In the simple case given, unlocking in the reverse order is not necessary to avoid a deadlock. However, as the code gets more complicated, unlocking in the reverse order helps you maintain proper lock ordering. Consider: A.lock(); B.lock(); Foo(); A.unlock(); Bar(); B.unlock(); If Bar() attempts to reacquire A, you’ve effectively broken your lock ordering. You’re … Read more