The approach with stream is not correct. See here https://stackoverflow.com/a/8701748/355264 Correct code from above link: Image img; using (var bmpTemp = new Bitmap(“image_file_path”)) { img = new Bitmap(bmpTemp); }
Most filesystems (but not all) use locking to guard concurrent access to the same file. The lock can be exclusive, so the first user to get the lock gets access – subsequent users get a “access denied” error. In your example scenario, user A will be able to read the file and gets the file … Read more
Since C++ 17 (VS2015) you can use the standard: #include <shared_mutex> typedef std::shared_mutex Lock; typedef std::unique_lock< Lock > WriteLock; typedef std::shared_lock< Lock > ReadLock; Lock myLock; void ReadFunction() { ReadLock r_lock(myLock); //Do reader stuff } void WriteFunction() { WriteLock w_lock(myLock); //Do writer stuff } For older compiler versions and standards you can use boost to … Read more
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): with … Read more
Perform a WaitOne on the event with a timeout value of zero. It will return true if the event is set, or false if the timeout occurs. In other words, true -> event is set, false -> event is not set.
You can’t pass normal multiprocessing.Lock objects to Pool methods, because they can’t be pickled. There are two ways to get around this. One is to create Manager() and pass a Manager.Lock(): def main(): iterable = [1, 2, 3, 4, 5] pool = multiprocessing.Pool() m = multiprocessing.Manager() l = m.Lock() func = partial(target, l) pool.map(func, iterable) … Read more
You will still need locks if you share state between threads. The GIL only protects the interpreter internally. You can still have inconsistent updates in your own code. For example: #!/usr/bin/env python import threading shared_balance = 0 class Deposit(threading.Thread): def run(self): for _ in xrange(1000000): global shared_balance balance = shared_balance balance += 100 shared_balance = … Read more
First of, please think long and hard if you really want to disable the Home button or any other button for that matter (e.g. the Back button), this is not something that should be done (at least most of the times, this is a bad design). I can speak only for myself, but if I … Read more
In your example, the sleeps mean that generally there is no contention. An uncontended lock is very fast. For this to matter, you would need a contended lock; if there are writes in that contention, they should be about the same (lock may even be quicker) – but if it is mostly reads (with a … Read more
run this and then try your insert… select * from yourTable with (holdlock,tablockx) here, you can lock it for 5 minutes: BEGIN TRANSACTION SELECT * FROM yourTable WITH (TABLOCKX, HOLDLOCK) WHERE 0 = 1 WAITFOR DELAY ’00:05′ ROLLBACK TRANSACTION