race-condition

问题 I`m making the multithread system on python 2.7. Basically, it has 3 thread and one singleton-class with shared data. Red arrow - invoke ; Blue arrow - access Every thread is separate class in a file. The file main.py import working and communication files, and shared data. Then main thread invoke working class in one thread and communication in another one thread. Herewith shared data, as only one instance of singleton, is passed in constructors of working class and communication class. File

问题 #include <pthread.h> #include <stdio.h> #include <unistd.h> #include <vector> #include <string> #include <iostream> FILE* fp; pthread_mutex_t demoMutex = PTHREAD_MUTEX_INITIALIZER; pthread_cond_t conditionVariable = PTHREAD_COND_INITIALIZER; unsigned int condition = 0; struct serverInfo { unsigned int serverId; pthread_t threadId; std::vector<std::string> queue; }; std::vector<serverInfo> serverInfoVector; void* printHello(void* threadId) { pthread_t* my_tid = (pthread_t*)threadId; pthread

问题 I would like to know if there is a real case scenario in which race condition problems can actually occur on an insertion query. So I have a table "User" with the following fields: User: iduser | idcompany | name | email I use a composite primary key for this table that is (iduser, idcompany). None of these fields is set to AUTO_INCREMENT. I get the value of the field "idcompany" through a session variable, so there's is not a real problem in this. However, I use a getNextUserId() function to

问题 This one has me a bit perplexed. I have a Shown event for a form, but the event's implementation doesn't process unless I display a MessageBox. Here is my code which does not work: private void MainForm_Shown(object sender, EventArgs e) { string[] arguments = Environment.GetCommandLineArgs(); foreach (var argument in arguments) { if (argument == "someArgs") { var something = doSomeStuff(); } } } Whenever I add a message box like this though, it works: private void MainForm_Shown(object sender

问题 I have implemented a "safe save" operation that goes something like this: Save some data to temporary file A Copy contents of A to final destination B Delete A I have a race condition at step 3 where Mac OS X will occasionally come back with error -47 ( fBsyErr ) when trying to delete the file using FSDeleteObject . I am completely confident I am the only one modifying this file and suspect the OS is doing something (e.g., background caching tasks) at the time I try to delete the file,

问题 I've implemented an Object cache like so: // Dictionary with weak keys & values private Map<Object, WeakReference<Object>> cache = new WeakHashMap<>(); private Object checkCache(Object obj) { // If it's in the cache, returned the cached copy. if (cache.containsKey(obj)) return cache.get(obj).get(); // Store it in, and return it. cache.put(obj, new WeakReference<>(obj)); return obj; } Picture the following race-condition scenario: cache.containsKey(obj) returns true The garbage collector kicks

问题 I am running a website with a LAMP system. Contents come from a database. For caching purposes, I create files on my webserver (containing cachable contents) (via fwrite() ). Every once in a while I am deleting the cache files (via unlink() ). File creation and deletion is done with a cronjob. My question is: what happens when a visitor to my website is currently browsing (=requesting from webserver) file A.php and I am trying to write to or delete this very same file A.php. To be precise:

问题 I have designed a prototype app with the following classes: Ticker class (discussed here) that has an assignable callback that will be executed every tick (specified by _tickInterval ) on a separate thread. SongPosition class that basically represents a position in a song. BeatClock class that assigns a callback to _ticker which is supposed to update _songpos and here I have a problem... Here is what Ticker class implementation looks like: #include <cstdint> #include <functional> #include

问题 I am trying to implement the Optimistic Locking for Race Condition. For that, I added an extra column lock_version in the Product: Model through migration. #Product: Model's new field: # attribute_1 # lock_version :integer(4) default(0), not null before_validation :method_1, :if => :recalculation_required_attribute def method_1 #### #### if self.lock_version == Product.find(self.id).lock_version Product.where(:id => self.id).update_all(attributes) self.attributes = attributes self.save! end

问题 I am working on an application written in Flask and backed by Amazon's DynamoDB accessed through boto. For a specific use case, we need to retrieve a value from a table and then make it unavailable for other users. However, by retrieving and then deleting the value, a race-condition could occur in between the retrieval and deletion. Is there any way to retrieve an item from a table and immediately delete or update it in an atomic fashion? 回答1: If your logic: get item delete without any