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  • Cocoa multhithreads, locks don't work

    - by Igor
    I have a threadMethod which shows in console robotMotorsStatus every 0.5 sec. But when I try to change robotMotorsStatus in changeRobotStatus method I receive an exception. Where I need to put locks in that program. #import "AppController.h" @implementation AppController extern char *robotMotorsStatus; - (IBAction)runThread:(id)sender { [self performSelectorInBackground:@selector(threadMethod) withObject:nil]; } - (void)threadMethod { char string_to_send[]="QFF001100\r"; //String prepared to the port sending (first inintialization) string_to_send[7] = robotMotorsStatus[0]; string_to_send[8] = robotMotorsStatus[1]; while(1){ [theLock lock]; usleep(500000); NSLog (@"Robot status %s", robotMotorsStatus); [theLock unlock]; } } - (IBAction)changeRobotStatus:(id)sender { robotMotorsStatus[0]='1'; }

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  • c++11 atomic ordering: extended total order memory_order_seq_cst for locks

    - by itaj
    There's this note in c++11 29.3-p3: [ Note: Although it is not explicitly required that S include locks, it can always be extended to an order that does include lock and unlock operations, since the ordering between those is already included in the "happens before" ordering. - end note ] What does it mean by "always"? I can understand that any certain implementation can be designed to support such an extended S. But in some general implementation that wasn't designed for it, I don't see that S can be extended so. I had sent this question to comp.std.c++ but got no answers there. http://groups.google.com/group/comp.std.c++/browse_frm/thread/5242fa70d0594d1b#

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  • No method error in controller create action

    - by user2799827
    I have read a number of Q&As on SO in search of some help on this but have so far not solved my issue. I am trying to teach myself ruby/rails, and as a test project, I want to create a list of tvshows and a list of characters where each tvshow has_many characters and each character belongs_to a specific show. I am sure I am doing something basic incorrectly. Any assistance would be greatly appreciated. here is the characters controller: class CharactersController < ApplicationController before_action :set_character, only: [:show, :edit, :update, :destroy] # GET /characters # GET /characters.json def index @characters = Character.all end # GET /characters/1 # GET /characters/1.json def show end # GET /characters/new def new @character = Character.new end # GET /characters/1/edit def edit end # POST /characters # POST /characters.json def create @character = @tvshow.characters.create(params[:character]) respond_to do |format| if @character.save format.html { redirect_to @character, notice: 'Character was successfully created.' } format.json { render action: 'show', status: :created, location: @character } else format.html { render action: 'new' } format.json { render json: @character.errors, status: :unprocessable_entity } end end end # PATCH/PUT /characters/1 # PATCH/PUT /characters/1.json def update respond_to do |format| if @character.update(character_params) format.html { redirect_to @character, notice: 'Character was successfully updated.' } format.json { head :no_content } else format.html { render action: 'edit' } format.json { render json: @character.errors, status: :unprocessable_entity } end end end # DELETE /characters/1 # DELETE /characters/1.json def destroy @character.destroy respond_to do |format| format.html { redirect_to characters_url } format.json { head :no_content } end end private # Use callbacks to share common setup or constraints between actions. def set_character @character = Character.find(params[:id]) end # Never trust parameters from the scary internet, only allow the white list through. def character_params params.require(:character).permit(:first_name, :last_name, :bio) end end character model: class Character < ActiveRecord::Base belongs_to :tvshow default_scope -> { order('created_at DESC') } validates :tvshow_id, presence: true end tvshow model: class Tvshow < ActiveRecord::Base has_many :characters, dependent: :destroy end error gets returned when I attempt to create a character. here is the full trace: app/controllers/characters_controller.rb:27:in `create' actionpack (4.0.0) lib/action_controller/metal/implicit_render.rb:4:in `send_action' actionpack (4.0.0) lib/abstract_controller/base.rb:189:in `process_action' actionpack (4.0.0) lib/action_controller/metal/rendering.rb:10:in `process_action' actionpack (4.0.0) lib/abstract_controller/callbacks.rb:18:in `block in process_action' activesupport (4.0.0) lib/active_support/callbacks.rb:413:in `_run__1211653665462320621__process_action__callbacks' activesupport (4.0.0) lib/active_support/callbacks.rb:80:in `run_callbacks' actionpack (4.0.0) lib/abstract_controller/callbacks.rb:17:in `process_action' actionpack (4.0.0) lib/action_controller/metal/rescue.rb:29:in `process_action' actionpack (4.0.0) lib/action_controller/metal/instrumentation.rb:31:in `block in process_action' activesupport (4.0.0) lib/active_support/notifications.rb:159:in `block in instrument' activesupport (4.0.0) lib/active_support/notifications/instrumenter.rb:20:in `instrument' activesupport (4.0.0) lib/active_support/notifications.rb:159:in `instrument' actionpack (4.0.0) lib/action_controller/metal/instrumentation.rb:30:in `process_action' actionpack (4.0.0) lib/action_controller/metal/params_wrapper.rb:245:in `process_action' activerecord (4.0.0) lib/active_record/railties/controller_runtime.rb:18:in `process_action' actionpack (4.0.0) lib/abstract_controller/base.rb:136:in `process' actionpack (4.0.0) lib/abstract_controller/rendering.rb:44:in `process' actionpack (4.0.0) lib/action_controller/metal.rb:195:in `dispatch' actionpack (4.0.0) lib/action_controller/metal/rack_delegation.rb:13:in `dispatch' actionpack (4.0.0) lib/action_controller/metal.rb:231:in `block in action' actionpack (4.0.0) lib/action_dispatch/routing/route_set.rb:80:in `call' actionpack (4.0.0) lib/action_dispatch/routing/route_set.rb:80:in `dispatch' actionpack (4.0.0) lib/action_dispatch/routing/route_set.rb:48:in `call' actionpack (4.0.0) lib/action_dispatch/journey/router.rb:71:in `block in call' actionpack (4.0.0) lib/action_dispatch/journey/router.rb:59:in `each' actionpack (4.0.0) lib/action_dispatch/journey/router.rb:59:in `call' actionpack (4.0.0) lib/action_dispatch/routing/route_set.rb:655:in `call' rack (1.5.2) lib/rack/etag.rb:23:in `call' rack (1.5.2) lib/rack/conditionalget.rb:35:in `call' rack (1.5.2) lib/rack/head.rb:11:in `call' actionpack (4.0.0) lib/action_dispatch/middleware/params_parser.rb:27:in `call' actionpack (4.0.0) lib/action_dispatch/middleware/flash.rb:241:in `call' rack (1.5.2) lib/rack/session/abstract/id.rb:225:in `context' rack (1.5.2) lib/rack/session/abstract/id.rb:220:in `call' actionpack (4.0.0) lib/action_dispatch/middleware/cookies.rb:486:in `call' activerecord (4.0.0) lib/active_record/query_cache.rb:36:in `call' activerecord (4.0.0) lib/active_record/connection_adapters/abstract/connection_pool.rb:626:in `call' activerecord (4.0.0) lib/active_record/migration.rb:369:in `call' actionpack (4.0.0) lib/action_dispatch/middleware/callbacks.rb:29:in `block in call' activesupport (4.0.0) lib/active_support/callbacks.rb:373:in `_run__2792846465963916895__call__callbacks' activesupport (4.0.0) lib/active_support/callbacks.rb:80:in `run_callbacks' actionpack (4.0.0) lib/action_dispatch/middleware/callbacks.rb:27:in `call' actionpack (4.0.0) lib/action_dispatch/middleware/reloader.rb:64:in `call' actionpack (4.0.0) lib/action_dispatch/middleware/remote_ip.rb:76:in `call' actionpack (4.0.0) lib/action_dispatch/middleware/debug_exceptions.rb:17:in `call' actionpack (4.0.0) lib/action_dispatch/middleware/show_exceptions.rb:30:in `call' railties (4.0.0) lib/rails/rack/logger.rb:38:in `call_app' railties (4.0.0) lib/rails/rack/logger.rb:21:in `block in call' activesupport (4.0.0) lib/active_support/tagged_logging.rb:67:in `block in tagged' activesupport (4.0.0) lib/active_support/tagged_logging.rb:25:in `tagged' activesupport (4.0.0) lib/active_support/tagged_logging.rb:67:in `tagged' railties (4.0.0) lib/rails/rack/logger.rb:21:in `call' actionpack (4.0.0) lib/action_dispatch/middleware/request_id.rb:21:in `call' rack (1.5.2) lib/rack/methodoverride.rb:21:in `call' rack (1.5.2) lib/rack/runtime.rb:17:in `call' activesupport (4.0.0) lib/active_support/cache/strategy/local_cache.rb:83:in `call' rack (1.5.2) lib/rack/lock.rb:17:in `call' actionpack (4.0.0) lib/action_dispatch/middleware/static.rb:64:in `call' railties (4.0.0) lib/rails/engine.rb:511:in `call' railties (4.0.0) lib/rails/application.rb:97:in `call' rack (1.5.2) lib/rack/lock.rb:17:in `call' rack (1.5.2) lib/rack/content_length.rb:14:in `call' rack (1.5.2) lib/rack/handler/webrick.rb:60:in `service' /Users/dariusgoore/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/webrick/httpserver.rb:138:in `service' /Users/dariusgoore/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/webrick/httpserver.rb:94:in `run' /Users/dariusgoore/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/webrick/server.rb:191:in `block in start_thread'

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  • How does Photoshop (Or drawing programs) blit?

    - by user146780
    I'm getting ready to make a drawing application in Windows. I'm just wondering, do drawing programs have a memory bitmap which they lock, then set each pixel, then blit? I don't understand how Photoshop can move entire layers without lag or flicker without using hardware acceleration. Also in a program like Expression Design, I could have 200 shapes and move them around all at once with no lag. I'm really wondering how this can be done without GPU help. I don't think super efficient algorithms could justify that? Thanks

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  • DispatcherOperations.Wait()

    - by Mark
    What happens if you call dispatcherOperation.Wait() on an operation that has already completed? Also, the docs say that it returns a DispatcherOperationStatus, but wouldn't that always be Completed since it (supposedly) doesn't return until it's done? I was trying to use it like this: private void Update() { while (ops.Count > 0) ops.Dequeue().Wait(); } public void Add(T item) { lock (sync) { if (dispatcher.CheckAccess()) { list.Add(item); OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, item)); } else { ops.Enqueue(dispatcher.BeginInvoke(new Action<T>(Add), item)); } } } I'm using this in WPF, so all the Add operations have to occur on the UI thread, but I figured I could basically just queue them up without having to wait for it to switch threads, and then just call Update() before any read operations to ensure that the list is up to date, but my program started hanging.

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  • Generating a set of files containing dumps of individual tables in a way that guarantees database co

    - by intuited
    I'd like to dump a MySQL database in such a way that a file is created for the definition of each table, and another file is created for the data in each table. I'd like this to be done in a way that guarantees database integrity by locking the entire database for the duration of the dump. What is the best way to do this? Similarly, what's the best way to lock the database while restoring a set of these dump files? edit I can't assume that mysql will have permission to write to files.

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  • Preventing dictionary attacks on a web application

    - by Kevin Pang
    What's the best way to prevent a dictionary attack? I've thought up several implementations but they all seem to have some flaw in them: Lock out a user after X failed login attempts. Problem: easy to turn into a denial of service attack, locking out many users in a short amount of time. Incrementally increase response time per failed login attempt on a username. Problem: dictionary attacks might use the same password but different usernames. Incrementally increase response time per failed login attempt from an IP address. Problem: easy to get around by spoofing IP address. Incrementally increase response time per failed login attempt within a session. Problem: easy to get around by creating a dictionary attack that fires up a new session on each attempt.

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  • Threading Problems in ActionScript 2.0?

    - by yar
    Is it possible to have concurrency problems (thread competition) in an onEnterFrame method in ActionScript 2.0? I have written this cheesy code as a guard: if (!busy) { // I suspect some threading problems: is that even possible in flash busy = true; movePanels(); busy = false; } but this is no assurance against thread competition. If so, how can I do a basic semaphore/lock? Note: I suspect threading problems in my app, but if they're impossible, I'll check my code differently.

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  • Should I make my MutexLock volatile?

    - by sje397
    I have some code in a function that goes something like this: void foo() { { // scope the locker MutexLocker locker(&mutex); // do some stuff.. } bar(); } The function call bar() also locks the mutex. I am having an issue whereby the program crashes (for someone else, who has not as yet provided a stack trace or more details) unless the mutex lock inside bar is disabled. Is it possible that some optimization is messing around with the way I have scoped the locker instance, and if so, would making it volatile fix it? Is that a bad idea? Thanks.

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  • Are SqlCipher open cursors a security concern?

    - by user1178479
    I'm using SqlCipher with content providers. Right now, when I want to lock the app I just clear out the cached password. However, the app can continue to work with any open cursors. This means that re-opening the app grants access to the sensitive data. I fix this issue on the surface by redirecting to a login screen if the app doesn't have passwords. However, I'm concerned if there are any security issues with these open cursors or if I should just continue to block UI access and not worry? SqlCipher's docs say that it reads/writes encrypted pages on the fly, as opposed to decrypting the entire DB, this makes me think that open cursors are still secure. The main concern here is that someone loses their phone and then a knowledgeable individual can use these open cursors to extract sensitive data.

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  • One account, multiple users, multiple shopping cart in a web application

    - by lemotdit
    I received a somewhat unusual request (imo) for a transactional web site. I have to implement the possibility of having multiple shopping cart for the same user. Those really are shopping carts, not order templates. I.E: A store with several departments ordering under the same account, but with a different person placing orders for a specific department only. Having more than one user per account is not an option since it would involve 'too much' management from the stores owner and the admins. Anyone had to deal with this before? The option so far is to have names for shopping cart, and a dropdown list or something alike after login to choose the cart with some kind of 'busy flag' to lock the cart if it's in use in another session.

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  • Fast way to pass a simple java object from one thread to another

    - by Adal
    I have a callback which receives an object. I make a copy of this object, and I must pass it on to another thread for further processing. It's very important for the callback to return as fast as possible. Ideally, the callback will write the copy to some sort of lock-free container. I only have the callback called from a single thread and one processing thread. I only need to pass a bunch of doubles to the other thread, and I know the maximum number of doubles (around 40). Any ideas? I'm not very familiar with Java, so I don't know the usual ways to pass stuff between threads.

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  • How to maipulate the shell output in php

    - by Mirage
    I am trying to write php script which does some shell functions like reporting. So i am starting with diskusage report I want in following format drive path ------------total-size --------free-space Nothing else My script is $output = shell_exec('df -h -T'); echo "<pre>$output</pre>"; and its ouput is like below Filesystem Type Size Used Avail Use% Mounted on /dev/sda6 ext3 92G 6.6G 81G 8% / none devtmpfs 3.9G 216K 3.9G 1% /dev none tmpfs 4.0G 176K 4.0G 1% /dev/shm none tmpfs 4.0G 1.1M 4.0G 1% /var/run none tmpfs 4.0G 0 4.0G 0% /var/lock none tmpfs 4.0G 0 4.0G 0% /lib/init/rw /dev/sdb1 ext3 459G 232G 204G 54% /media/Server /dev/sdb2 fuseblk 466G 254G 212G 55% /media/BACKUPS /dev/sda5 fuseblk 738G 243G 495G 33% /media/virtual_machines How can i convert that ouput into my forn\matted output

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  • Mysql Master Slave Replication on Large Database table (how to sync initial data)

    - by Brian Lovett
    We have a production server and a dev server. We have found that backups are nearly impossible on the production server because of the query volume we experience. So, we're looking at setting up replication with our dev server being the slave. This is ideal because we can afford to lock the tables on that server and additionally it will be nice to have up to date data for the developers. Now, the issues. The production server can't really be taken down or locked at this point, at least not easily. We have a high query volume and fairly large 30+ GB innodb tables. Both servers are running all innodb and are also both on mysql 5.1. What can we do to sync the data initially to get replication started? I've tried a few options, but so far, none have worked.

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  • Is this query safe in SQL Server?

    - by xaw
    I have this SQL update query: UPDATE table1 SET table1.field1 = 1 WHERE table1.id NOT IN (SELECT table2.table1id FROM table2); Other portions of the application can add records to table2 which use the field table1id to reference table1. The goal here is to remove records from table1 which aren't referenced by table2. Does SQL Server automatically lock table2 with this kind of query so that a new record can't be added to table2 while executing this query? I've also considered: UPDATE table1 SET field1 = 1 WHERE 0 = (SELECT COUNT(*) FROM table2 WHERE table1.id = table2.table1id); Which seems possibly safer, but much slower (because a SELECT would be called on each row of table1 instead of just one select for the NOT IN)

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  • [MySQL, InnoDb] Rating place

    - by Pavel
    I'm trying to generate rating place table using following receipt http://stackoverflow.com/questions/1776821/assign-places-in-the-rating-mysql-php but my database is high loaded. I tried not to create table, but use MEMORY TABLE and update it using following SQL query insert into tops (uid) select uid from users order by exp desc; but got the following MySQL error Deadlock found when trying to get lock; try restarting transaction because there are too many queries until SQL select is being executed. How to solve this problem? P.S. CREATE TABLE tops as SELECT work almost fine except high server load... up to load average: 50 if tops are non-memory table. My table users has near 4.5 millions of rows. Thanks for any advices.

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  • Could not find generator mini_test:install

    - by David James
    I expected these generators to be available: $ rails g Usage: rails generate GENERATOR [args] [options] MiniTest: mini_test:controller mini_test:helper mini_test:install mini_test:mailer mini_test:model mini_test:scaffold So I ran: $ rails g mini_test:install But got this error: Could not find generator mini_test:install. As for my environment, here is the relevant portion of my Gemfile: group :test, :development do gem 'minitest-rails' end And the resulting portions of my Gemfile.lock: minitest (2.12.1) minitest-rails (0.0.7) minitest (~> 2.12) rails (~> 3.1) I am now in the process of debugging this. I would appreciate any tips. In any case, I will report back.

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  • How can I kill MySQL queries every 60 seconds in Windows?

    - by Ethan Allen
    I want to check my MySQL server every minute and kill queries that have run longer than 150 seconds. The main reason I want to do this is because I don't want queries from certain people to lock up the DB for everyone else. I know this is not the ultimate solution to the problem, but at least it's a fallback in case something goes wrong with a query. I don't have a slave DB (this is just an at-home project). I'd like to schedule a script to run that does this for me. I'm unfamiliar with Perl or Ruby and I need it done on my Windows 2008 Server box. I've looked into creating a simple cmd line script, but that doesn't seem to be possible. I know currently I can do something like this but I have to do it manually: mysqladmin processlist mysqladmin kill Anyone have any ideas or examples on how I could do this?

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  • how to configure hibernate not to update @Version on each access to entity

    - by radai
    i have a simple query that returns an entity, and when i look at hibernate SQL output i see that when i execute this query hibernate updates the @Version field (on each consecutive read the @version field is updated). i dont modify anything in the entity i fetch, and i dont pass is as an argument to either persist or merge. this effectively means every read i make turns into a read+write. i've tried setting the lock mode t oboth NONE (jpa 2) and READ (jpa 1) to no avail. is there any way to achieve this? if so, is there any way to set this as the default behavior in persistence.xml in some way ? im using jpa2 over hibernate 3.6

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  • How do I prevent Window resizing when the Workstation is Locked then Unlocked?

    - by Terry
    We have an application that is run in multi-monitor environments. Users normally have the application dialog spread out to span multiple mointors. If the user locks the workstation, and then unlocks it, our application is told to resize. Our users find this behavior frustrating, as they then spend some time restoring the previous layout. We're not yet sure whether it is the graphics driver requesting the resize or Windows. Hopefully through this question, it will become clearer which component is responsible, Popular applications like (File) Explorer and Firefox behave the same way in this setup. To replicate just: open Explorer (Win+E) drag the Explorer window to being horizontally larger than 1 screen lock workstation (Win+L), unlock the application should now resize to being solely on 1 screen How do I prevent Window resizing when the Workstation is Locked then Unlocked? Will we need to code in checks for (un)locking? Is there another mechanism we're not aware of?

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  • How to detect an active x component that does not respond any more?

    - by koschi
    My application is written in C++ and uses the Qt framework. I use the QAxWidget class to access an active x component. Now I need some kind of mechanism that notifies my application each time the active x component has crashed or does not respond any more (due to dead lock or infinite loop). (1) can easily been done by watching the external process of the active x component. But maybe there is a more elegant approach? But how can (2) be implemented?

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  • Devise role based routing

    - by teknull
    I have an app with multiple users. Each user as a theoretical role (user, client, etc). I've designed a view/controller for each user type. I want to be able to login each type of user do a different root url and lock them to it. Originally I was going to add a column to Users in Devise called role and so I can differentiate the users. The problem I'm having is how to say in routes.rb if current_user.role == "client" root :to = 'controller#index' Once they are logged in to the page I also want to keep them from being able to visit any of my other paths ie: domain.com/calls domain.com/units I've been looking into cancan to run alongside Devise but I'm not sure if this is the answer.

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  • .NET "Timer" would block other method calls?

    - by Ricky
    Hi guys: In ASP.NET 3.5, we suspect a delegate triggering by a "Timer" will block other method calls. From logs, some function calls will wait for the finishing of the delegate and continue to work. Is it true? If yes, what workaround can I do? PS: The delegate contains codes to use WCF to retrieve data and the following code private void Replace<T>(ref IList<T> src, IList<T> des) { lock(src) { while (src.Count > 0) { GC.SuppressFinalize(src.ElementAt(0)); src.RemoveAt(0); } GC.SuppressFinalize(src); src = des; } } Thanks a lot.

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  • Do I need to syncronize thread access to an int

    - by Martin Harris
    I've just written a method that is called by multiple threads simultaneously and I need to keep track of when all the threads have completed, the code uses this pattern: private void RunReport() { _reportsRunning++; try { //code to run the report } finally { _reportsRunning--; } } This is the only place within the code that _reportsRunning's value is changed, and the method takes about a second to run. Occasionally when I have more than six or so threads running reports together the final result for _reportsRunning can get down to -1, if I wrap the calls to _runningReports++ and _runningReports-- in a lock then the behaviour appears to be correct and consistant. So, to the question: When I was learning multithreading in C++ I was taught that you didn't need to synchronize calls to increment and decrement operations because they were always one assembly instruction and therefore it was impossible for the thread to be switched out mid-call. Was I taught correctly, and if so how come that doesn't hold true for C#?

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  • AIR app still running when the iphone is blocked?

    - by nmarti
    I just made a simple game with flash professional 6.0 and adobe AIR sdk 3.4 for iPhone. The problem is this: when I lock the iphone pressing the power button, the screen switches off as usual, but the music of the game still sounds. If I exit the game pressing the home button it exits fine. Is only when locking the phone with the app opened. Also, I opted-out of multitasking for my app, so if I close my app with the home button and I reload it, it loads the main menu. Anyone knows how can I solve this?

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