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• Which logs will tell me about the Touchpad and Keyboard locking up?

  - by Sepero

  I have an Asus N53SM laptop that I leave running for several weeks at a time. I never put it in hibernate or suspend, I only close the lid when I'm not using it. After a few days or weeks of running, the touchpad and keyboard will Both lock up (at the same time) for no apparent reason. I could be just surfing the internet when it happens. The touchpad and keyboard seem to only lock up when I'm actively using the laptop (not when idle), which may mean it's related to something I press, but I'm not sure? The touchpad never locks or unlocks when Pressing FN and the designated touchpad lock key (it does not seem to work on Linux). While the touchpad and keyboard are locked, I am able to plug in my USB mouse and successfully use it to control the screen cursor. I can also remotely get into the system with vnc and ssh, everything seems to run fine there as well. No processes appear out of control. It's just the laptops physical touchpad and keyboard that are locking up. How might I go about diagnosing this problem? What system logs to look at? (anything specific to look for in them?) Perhaps I should try reloading some modules? Any thing else I should inspect?

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• Disk space suddenly 100% used?

  - by dannymcc

  I'm trying to identify why, suddenly, 100% of our disk space is in use. I have already rebooted but the issue persists. Here are the outputs of some commands that are showing some strange (for me) results: danny@hydrogen:~$ df -h Filesystem Size Used Avail Use% Mounted on /dev/cciss/c0d0p1 130G 122G 949M 100% / none 1.9G 196K 1.9G 1% /dev none 2.0G 0 2.0G 0% /dev/shm none 2.0G 40K 2.0G 1% /var/run none 2.0G 0 2.0G 0% /var/lock none 2.0G 0 2.0G 0% /lib/init/rw danny@hydrogen:/$ sudo du -chs / du: cannot access `/proc/1662/task/1662/fd/4': No such file or directory du: cannot access `/proc/1662/task/1662/fdinfo/4': No such file or directory du: cannot access `/proc/1662/fd/4': No such file or directory du: cannot access `/proc/1662/fdinfo/4': No such file or directory danny@hydrogen:/$ df Filesystem 1K-blocks Used Available Use% Mounted on /dev/cciss/c0d0p1 135342296 128144108 323104 100% / none 1991336 196 1991140 1% /dev none 1995788 0 1995788 0% /dev/shm none 1995788 40 1995748 1% /var/run none 1995788 0 1995788 0% /var/lock none 1995788 0 1995788 0% /lib/init/rw danny@hydrogen:/$ mount /dev/cciss/c0d0p1 on / type ext4 (rw,errors=remount-ro) proc on /proc type proc (rw,noexec,nosuid,nodev) none on /sys type sysfs (rw,noexec,nosuid,nodev) none on /sys/fs/fuse/connections type fusectl (rw) none on /sys/kernel/debug type debugfs (rw) none on /sys/kernel/security type securityfs (rw) none on /dev type devtmpfs (rw,mode=0755) none on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=0620) none on /dev/shm type tmpfs (rw,nosuid,nodev) none on /var/run type tmpfs (rw,nosuid,mode=0755) none on /var/lock type tmpfs (rw,noexec,nosuid,nodev) none on /lib/init/rw type tmpfs (rw,nosuid,mode=0755) danny@hydrogen:/$ sudo du -h --max-depth=1 634M ./premvet_sync 5.6M ./etc 4.0K ./opt 16K ./lost+found 7.4M ./bin 623M ./lib 196K ./dev 0 ./sys 4.0K ./srv 4.0K ./cdrom 8.0K ./media 52K ./tmp ... it hangs for ages here..... The server is running Ubuntu 10.04.4 LTS. System load: 2.85 Temperature: 8 C Usage of /: 94.7% of 129.07GB Processes: 132 Memory usage: 39% Users logged in: 0 Swap usage: 0% IP address for eth0: 192.168.1.124 => / is using 94.7% of 129.07GB I'm struggling to comprehend why this is happening! Any pointers would be appreciated.

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• Diagnosing xmodmap errors

  - by intuited

  I'm getting this error when trying to use xmodmap to get rid of caps lock: $ xmodmap -e 'clear Lock' X Error of failed request: BadValue (integer parameter out of range for operation) Major opcode of failed request: 118 (X_SetModifierMapping) Value in failed request: 0x17 Serial number of failed request: 8 Current serial number in output stream: 8 I'm running xfce on Maverick "10.10" Meercat. This problem did not occur before I added the Keyboard Layouts applet to a panel; before doing that, I was able to run my xmodmap script to swap Esc and CapsLock: !Remap Caps_Lock as Escape remove Lock = Caps_Lock keysym Caps_Lock = Escape It may be relevant that I chose alt-capslock as the keyboard switch combo in the Keyboard Layouts preferences. I've had a similar problem before, on a different machine, running openbox. On that machine, this problem started when I upgraded to Lucid, and has persisted in Maverick (release 10.10). I reported a bug in xorg. However, it remains unclear whether it's really a problem with xorg, or if I'm just doing something wrong with my configuration. Have other people experienced this problem? Can someone shed some light on what's going on here? It seems there are quite a few layers involved, and I don't understand any of them particularly well, so any information would be helpful. update I've discovered that the problem is specifically triggered by adding the Canada layout variant "Multilingual" (ca-multix). If I instead add the variant "Multilingual (first part)", the problem does not occur. I think this will probably end up being a usable workaround, but I don't yet know what the difference between these variants is. I've filed a freedesktop issue, and am commenting on a related ubuntu issue.

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• Session state provider and atomic operations

  - by vtortola

  Hi, I've been thinking about this and it is blowing my mind... How does a session state provider properly works internally? I mean, I tried to write a custom session state provider based on Azure Tables or Blobs, but quickly I realized that because there is no way to ensure an atomic operation or establish a lock, race conditions are suitable to happen when several web servers do operation on that shared information. I know that there is a SQL Server Session State Provider (SQLS-SSP) and people is happy with it, so I guess that it's using some kind of transaction isolation level in order to accomplish some degree of concurrent safety, like checking is the data is lock (a simple column), locking it if not and returning the data in an atomic operation, but is that so? what does happen if the data is lock? does it returns an error? block the call for a while? returns it in read-only fashion? Cloud computing paradigms could be somehow new, but webfarms have been here for a while, so as I'm pretty new on it... do you recommend any good lecture about the topic? Thanks.

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• reinstalling phpmyadmin

  - by explorex

  EDIT:: installed mysql-server but no phpmyadmin (since phpmyadmin was installed before mysql, that resulted an error). How to reinstall phpmyadmin with database (there is no phpmyadmin datbase)? unstalling it and reinstalling it didn't help. i was trying to install phpmyadmin (and zend framework) through synaptic manager but in the middle i was prompted for password i thought it was phpmyadmin password and i proceeded but i got error and i aborted. and then again i tried to reinstall, it reinstalled but i am not getting phpmyadmin. EDIT::The following is invalid so please don't bother apache is running but mysql is not some of it's characteristics are: santosh@explorer:~$ mysql ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2) santosh@explorer:~$ sudo apt-get install mysql-server E: Could not get lock /var/lib/dpkg/lock - open (11: Resource temporarily unavailable) E: Unable to lock the administration directory (/var/lib/dpkg/), is another process using it? Should i be asking this question here or stackoverflow? UPDATES:: after restarting my computer santosh@explorer:~$ sudo service mysql start [sudo] password for santosh: mysql: unrecognized service UPDATES:: santosh@explorer:~$ sudo apt-get install mysql Reading package lists... Done Building dependency tree Reading state information... Done E: Unable to locate package mysql

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• Ubuntu hangs after replugging the modem

  - by Iftekhar Ahmed Shafi

  I am facing this issue on Ubuntu 12.04, which is for my Wimax modem with beceem chipset. If I replug the device Ubuntu goes in hang state. Its happens very often. If I plug the USB and restart it works most of the time. But it is very annoying to restart every time it hangs. The modem works smoothly in Windows 7. And it used to work OK in Ubuntu 11.10. Jun 13 19:25:54 iftekhar-HP-520-Notebook-PC dbus[1102]: [system] Activating service name='org.freedesktop.UDisks' (using servicehelper) Jun 13 19:25:54 iftekhar-HP-520-Notebook-PC dbus[1102]: [system] Successfully activated service 'org.freedesktop.UDisks' Jun 13 19:26:00 iftekhar-HP-520-Notebook-PC goa[2168]: goa-daemon version 3.4.0 starting [main.c:112, main()] Jun 13 19:26:47 iftekhar-HP-520-Notebook-PC udevd[432]: timeout 'cdrom_id --lock-media /dev/sr1' Jun 13 19:26:48 iftekhar-HP-520-Notebook-PC udevd[432]: timeout: killing 'cdrom_id --lock-media /dev/sr1' [1072] Jun 13 19:26:49 iftekhar-HP-520-Notebook-PC kernel: [ 85.820162] sr 2:0:0:0: Device offlined - not ready after error recovery Jun 13 19:26:49 iftekhar-HP-520-Notebook-PC udevd[432]: timeout: killing 'cdrom_id --lock-media /dev/sr1' [1072] Jun 13 19:27:20 udevd[432]: last message repeated 31 times Jun 13 19:27:25 udevd[432]: last message repeated 4 times What can I do to avoid this hangs and restarts?

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• How to fix out the error dpkg: error processing colord (--configure):

  - by ranjitpradhan

  I have upgrade my ubuntu from 11.10 to 12.04. at last i can found that when i tries to install some packages it shows a error. after reading some blog i tried to fix that error by "sudo dpkg --configure -a". but when i run this command it show another error this Setting up colord (0.1.16-2) ... useradd: cannot lock /etc/passwd; try again later. adduser: `/usr/sbin/useradd -d /var/lib/colord -g colord -s /bin/false -u 115 colord' returned error code 1. Exiting. dpkg: error processing colord (--configure): subprocess installed post-installation script returned error exit status 1 Setting up whoopsie (0.1.32) ... useradd: cannot lock /etc/passwd; try again later. adduser: `/usr/sbin/useradd -d /nonexistent -g whoopsie -s /bin/false -u 115 whoopsie' returned error code 1. Exiting. dpkg: error processing whoopsie (--configure): subprocess installed post-installation script returned error exit status 1 Setting up lightdm (1.2.1-0ubuntu1) ... Adding system user `lightdm' (UID 115) ... Adding new user `lightdm' (UID 115) with group `lightdm' ... useradd: cannot lock /etc/passwd; try again later. adduser: `/usr/sbin/useradd -d /var/lib/lightdm -g lightdm -s /bin/false -u 115 lightdm' returned error code 1. Exiting. dpkg: error processing lightdm (--configure): subprocess installed post-installation script returned error exit status 1 dpkg: dependency problems prevent configuration of ubuntu-desktop: ubuntu-desktop depends on lightdm; however: Package lightdm is not configured yet. dpkg: error processing ubuntu-desktop (--configure): dependency problems - leaving unconfigured Errors were encountered while processing: colord whoopsie lightdm ubuntu-desktop what can i do now ?

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• Broken Package on Update Manager

  - by Widy Graycloud

  I dont know what's wrong with my update manager.. It says that the softwares that I installed was broken. Maybe because I force shutdown my laptop, because Ubuntu wont shutdown,showing up desktop wallpaper but not title bar and launcher, but It won't shut down (+that's another bug). I've just update the broken softwares. the size is 60 to 70 MB.. But It doesn't work. Now I cannot update or install any software from Update Manager or Ubuntu Software Center. Can anybody tellme what's wrong? This is what appears when I use Update Manager I use Ubuntu Software Center, and this message appeared I chose repair and when it update the broken softwares using Ubuntu Software Center. It failed. And show up this message. The problem is I can't update or install any program from Ubuntu Software Center and Device Manager anymore. (I closed allprograms include ubuntu software center,and device manager in this case). Some one helpme? I tried to use apt-get install -f in terminal but it shows message like this: E: Could not open lock file /var/lib/dpkg/lock - open (13: Permission denied) E: Unable to lock the administration directory (/var/lib/dpkg/), are you root?

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• Touchpad and Keyboard both stop working after long uptime

  - by Sepero

  I have an Asus N53SM laptop that I leave running for several weeks at a time. I never put it in hibernate or suspend, I only close the lid when I'm not using it. After a few days or weeks of running, the touchpad and keyboard will Both lock up (at the same time) for no apparent reason. I could be just surfing the internet when it happens. The touchpad and keyboard seem to only lock up when I'm actively using the laptop (not when idle), which may mean it's related to something I press, but I'm not sure? The touchpad never locks or unlocks when Pressing FN and the designated touchpad lock key (it does not seem to work on Linux). While the touchpad and keyboard are locked, I am able to plug in my USB mouse and successfully use it to control the screen cursor. I can also remotely get into the system with vnc and ssh, everything seems to run fine there as well. No processes appear out of control. It's just the laptops physical touchpad and keyboard that are locking up. How might I go about diagnosing this problem? What system logs to look at? (anything specific to look for in them?) Perhaps I should try reloading some modules? Any thing else I should inspect?

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• ????????????3?????

  - by Feng

  ?? ??blog?????oracle????????????,??????????????,??????: ?????????. ???????: ??????????,????????; ????????????,?” ???”??. 1. OS swapping/paging ??????concurrency??????? Oracle?????????, ??latch/mutex???????”?”,??????????????/???(????????????,??????????????????). ????OS??????swapping/paging????,???????????,??latch/mutex???????,????????????hung/slow???. ??swapping/paging??????: a). ???? b). ??????; ?????, ?????????????? c). ?????/????? ????????????????? ???????: Lock SGA, ??SGA(???latch/mutex)???pin???????swapping???. ???SGA??????,????large page(hugepage)??,??latch/mutex??/?????. 2. SGA resizing?????????? ?AMM/ASMM??????????, shared pool?buffer cache?????component????????????,??ora-4031???.??????????,???????resize????????????(?latch/mutex?????)?????, ?????????latch/mutex??. ????shared pool?resize??????,??latch/mutex???????. ?????????:  ?????bug; ???????????,??resize???????????????,???????????. ??bug?fix??????????impact, ???????????. ???????: 1). ??buffer cache?shared pool??(???????????,?????????) 2). ??resize???????16?? alter system set "_memory_broker_stat_interval"=999; Disable AMM/ASMM?????????,?????: ??ora-4031????????????. 3. DDL?????????? ??????????????????. ???????????DDL (??grant, ?????, ????????),???????????SQL?????invalidate?;????????SQL????????????,?????????hard parse ? SQL??????. ??????? “hardparse storm”, latch/mutex????????, ??library cache lock/row cache lock????; ??????????slow/hung. ???????: ???????????DDL ??????????,???????????,?? “????????????3?????"?

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• Python: nonblocking read from stdout of threaded subprocess

  - by sberry2A

  I have a script (worker.py) that prints unbuffered output in the form... 1 2 3 . . . n where n is some constant number of iterations a loop in this script will make. In another script (service_controller.py) I start a number of threads, each of which starts a subprocess using subprocess.Popen(stdout=subprocess.PIPE, ...); Now, in my main thread (service_controller.py) I want to read the output of each thread's worker.py subprocess and use it to calculate an estimate for the time remaining till completion. I have all of the logic working that reads the stdout from worker.py and determines the last printed number. The problem is that I can not figure out how to do this in a non-blocking way. If I read a constant bufsize then each read will end up waiting for the same data from each of the workers. I have tried numerous ways including using fcntl, select + os.read, etc. What is my best option here? I can post my source if needed, but I figured the explanation describes the problem well enough. Thanks for any help here. EDIT Adding sample code I have a worker that starts a subprocess. class WorkerThread(threading.Thread): def __init__(self): self.completed = 0 self.process = None self.lock = threading.RLock() threading.Thread.__init__(self) def run(self): cmd = ["/path/to/script", "arg1", "arg2"] self.process = subprocess.Popen(cmd, stdout=subprocess.PIPE, bufsize=1, shell=False) #flags = fcntl.fcntl(self.process.stdout, fcntl.F_GETFL) #fcntl.fcntl(self.process.stdout.fileno(), fcntl.F_SETFL, flags | os.O_NONBLOCK) def get_completed(self): self.lock.acquire(); fd = select.select([self.process.stdout.fileno()], [], [], 5)[0] if fd: self.data += os.read(fd, 1) try: self.completed = int(self.data.split("\n")[-2]) except IndexError: pass self.lock.release() return self.completed I then have a ThreadManager. class ThreadManager(): def __init__(self): self.pool = [] self.running = [] self.lock = threading.Lock() def clean_pool(self, pool): for worker in [x for x in pool is not x.isAlive()]: worker.join() pool.remove(worker) del worker return pool def run(self, concurrent=5): while len(self.running) + len(self.pool) > 0: self.clean_pool(self.running) n = min(max(concurrent - len(self.running), 0), len(self.pool)) if n > 0: for worker in self.pool[0:n]: worker.start() self.running.extend(self.pool[0:n]) del self.pool[0:n] time.sleep(.01) for worker in self.running + self.pool: worker.join() and some code to run it. threadManager = ThreadManager() for i in xrange(0, 5): threadManager.pool.append(WorkerThread()) threadManager.run() I have stripped out a log of the other code in hopes to try to pinpoint the issue.

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• Unlocking a mutex from a different thread (C++)

  - by dan

  I'm using the C++ boost::thread library, which in my case means I'm using pthreads. Officially, a mutex must be unlocked from the same thread which locks it, and I want the effect of being able to lock in one thread and then unlock in another. There are many ways to accomplish this. One possibility would be to write a new mutex class which allows this behavior. For example: class inter_thread_mutex{ bool locked; boost::mutex mx; boost::condition_variable cv; public: void lock(){ boost::unique_lock<boost::mutex> lck(mx); while(locked) cv.wait(lck); locked=true; } void unlock(){ { boost::lock_guard<boost::mutex> lck(mx); if(!locked) error(); locked=false; } cv.notify_one(); } // bool try_lock(); void error(); etc. } I should point out that the above code doesn't guarantee FIFO access, since if one thread calls lock() while another calls unlock(), this first thread may acquire the lock ahead of other threads which are waiting. (Come to think of it, the boost::thread documentation doesn't appear to make any explicit scheduling guarantees for either mutexes or condition variables). But let's just ignore that (and any other bugs) for now. My question is, if I decide to go this route, would I be able to use such a mutex as a model for the boost Lockable concept. For example, would anything go wrong if I use a boost::unique_lock< inter_thread_mutex for RAII-style access, and then pass this lock to boost::condition_variable_any.wait(), etc. On one hand I don't see why not. On the other hand, "I don't see why not" is usually a very bad way of determining whether something will work. The reason I ask is that if it turns out that I have to write wrapper classes for RAII locks and condition variables and whatever else, then I'd rather just find some other way to achieve the same effect.

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• Zero code coverage with cobertura 1.9.2 but tests are working

  - by eraonel

  I run the code coverage target: <junit fork="yes" dir="${basedir}" failureProperty="test.failed"> <!-- Note the classpath order: instrumented classes are before the original (uninstrumented) classes. This is important. --> <classpath path="${instrumented.dir}" /> <classpath path="${classes.dir}" /> <classpath refid="classpath" /> <!-- The instrumented classes reference classes used by the Cobertura runtime, so Cobertura and its dependencies must be on your classpath. --> <classpath refid="cobertura.classpath" /> <formatter type="xml" /> <!--<test name="${testcase}" todir="${reports.xml.dir}" if="testcase" />--> <batchtest fork="yes" todir="${reports.xml.dir}"> <fileset dir="${classes.dir}"> <include name="**/generated/AllTests.class" /> </fileset> </batchtest> </junit> <junitreport todir="${reports.xml.dir}"> <fileset dir="${reports.xml.dir}"> <include name="TEST-*.xml" /> </fileset> <report format="frames" todir="${reports.html.dir}" /> </junitreport> Then I get the following output ( when using fork="true"): java.lang.reflect.InvocationTargetException at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:585) at net.sourceforge.cobertura.util.FileLocker.lock(FileLocker.java:124) at net.sourceforge.cobertura.coveragedata.ProjectData.saveGlobalProjectData(ProjectData.java:331) at net.sourceforge.cobertura.coveragedata.SaveTimer.run(SaveTimer.java:31) at java.lang.Thread.run(Thread.java:595) Caused by: java.io.IOException: No locks available at sun.nio.ch.FileChannelImpl.lock0(Native Method) at sun.nio.ch.FileChannelImpl.lock(FileChannelImpl.java:784) at java.nio.channels.FileChannel.lock(FileChannel.java:865) ... 8 more --------------------------------------- Unable to get lock on /vobs/rnc/rrt/roam2/roamSs/RoamMao_swb/RoamMao_bldu/ant_build/cobertura.ser.lock: null This is known to happen on Linux kernel 2.6.20. Make sure cobertura.jar is in the root classpath of the jvm process running the instrumented code. If the instrumented code is running in a web server, this means cobertura.jar should be in the web server's lib directory. Don't put multiple copies of cobertura.jar in different WEB-INF/lib directories. Only one classloader should load cobertura. It should be the root classloader. I am using Ant 1.7.0 and cobertura 1.9.2. Any ideas why there is no coverage? Test run ok as I see in my target. I have tried to switch java versions ( 1.5.0_06 and 1.6.0_10) but no difference.

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• Snap App Windows to Pre-Defined Screen Sections with Acer GridVista

  - by Asian Angel

  The window snapping feature in Windows 7 and the ability to organize monitor(s) into specific gridded sections have both become popular lately. If you love the idea of having both combined in a single software then join us as we look at Acer GridVista. Note: Acer GridVista works with Windows XP, Vista, & 7. It will also work with dual monitors. Setup Acer GridVista comes in a zip file format and at first you might assume that it is portable in nature but it is not. Once you unzip the enclosed folder you will need to double click on “Setup.exe” to install the program. Acer GridVista in Action Once you have installed the program and started it up all that you will notice at first is the new “System Tray Icon”. Here you can see the “Context Menu”… The only menu command that you will likely use most of the time is the “Grid Configuration Command”. Notice that for our single monitor setup that it lists “Display 1”. The “Single Setting” is enabled by default and you can easily choose the layout that best suits your needs. The enabled layout style will always be highlighted in yellow for easy reference. For our example we chose the “Triple (primary at right)” layout style. Each section will be specifically numbered as shown here. Do not worry…the grid and numbers only appear for a moment and then become invisible again until you move an app window into that section/area of your screen. On every regular app window that you open you will notice three new buttons in the upper right corner. Here is what each of these new buttons do: Acer GridVista Extensions (Transparent, Send To Window Grid, About Acer GridVista): Viewable in a drop-down menu Lock To Grid (Enable/Disable): Enabled by default –> Note: Set to disable on a particular window to keep it free of the “grid locking function” Always On Top (Enable/Disable): Disabled by default A good look at the “Extensions Drop-Down Menu” where you can set an app window to be transparent or send it to a specific screen section on your monitor(s). If you open an app it will not automatically lock into a specific section. To lock the window into a specific section drag-and-drop the app window into the desired section. Notice the red outline and highlighted number on “Section 2” below. The red outline and highlighted number serves as an indicator that if you release the app window at that moment it will lock into the outlined/highlighted section. Now that Notepad is locked into “Section 2” you can see that it is maximized within that section. Continue to drag-and-drop your app windows into the appropriate sections as desired…apps can still be reduced to the “Taskbar” the same as before. Options These are the options available for Acer GridVista… Conclusion If you have been wanting the ability to “snap” windows and organize them into specific screen areas then Acer GridVista is definitely a program that you should try out. Links Download Acer GridVista at Softpedia View detailed information at the Acer GridVista Homepage Similar Articles Productive Geek Tips Multitask Like a Pro with AquaSnapHelp Troubleshoot the Blue Screen of Death by Preventing Automatic RebootAdd Windows 7’s AeroSnap Feature to Vista and XPResize Windows to Specific Dimensions Easily With SizerKeyboard Ninja: Assign a Hotkey to any Window TouchFreeze Alternative in AutoHotkey The Icy Undertow Desktop Windows Home Server – Backup to LAN The Clear & Clean Desktop Use This Bookmarklet to Easily Get Albums Use AutoHotkey to Assign a Hotkey to a Specific Window Latest Software Reviews Tinyhacker Random Tips DVDFab 6 Revo Uninstaller Pro Registry Mechanic 9 for Windows PC Tools Internet Security Suite 2010 Playing Games In Chrome Made Easier Stop In The Name Of Love (Firefox addon) Chitika iPad Labs Gives Live iPad Sale Stats Heaven & Hell Finder Icon Using TrueCrypt to Secure Your Data Quickly Schedule Meetings With NeedtoMeet

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• C++ thread safety - exchange data between worker and controller

  - by peterchen

  I still feel a bit unsafe about the topic and hope you folks can help me - For passing data (configuration or results) between a worker thread polling something and a controlling thread interested in the most recent data, I've ended up using more or less the following pattern repeatedly: Mutex m; tData * stage; // temporary, accessed concurrently // send data, gives up ownership, receives old stage if any tData * Send(tData * newData) { ScopedLock lock(m); swap(newData, stage); return newData; } // receiving thread fetches latest data here tData * Fetch(tData * prev) { ScopedLock lock(m); if (stage != 0) { // ... release prev prev = stage; stage = 0; } return prev; // now current } Note: This is not supposed to be a full producer-consumer queue, only the msot recent data is relevant. Also, I've skimmed ressource management somewhat here. When necessary I'm using two such stages: one to send config changes to the worker, and for sending back results. Now, my questions assuming that ScopedLock implements a full memory barrier: do stage and/or workerData need to be volatile? is volatile necessary for tData members? can I use smart pointers instead of the raw pointers - say boost::shared_ptr? Anything else that can go wrong? I am basically trying to avoid "volatile infection" spreading into tData, and minimize lock contention (a lock free implementation seems possible, too). However, I'm not sure if this is the easiest solution. ScopedLock acts as a full memory barrier. Since all this is more or less platform dependent, let's say Visual C++ x86 or x64, though differences/notes for other platforms are welcome, too. (a prelimenary "thanks but" for recommending libraries such as Intel TBB - I am trying to understand the platform issues here)

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• SQL deadlock on delete then bulk insert

  - by StarLite

  I have an issue with a deadlock in SQL Server that I haven't been able to resolve. Basically I have a large number of concurrent connections (from many machines) that are executing transactions where they first delete a range of entries and then re-insert entries within the same range with a bulk insert. Essentially, the transaction looks like this BEGIN TRANSACTION T1 DELETE FROM [TableName] WITH( XLOCK HOLDLOCK ) WHERE [Id]=@Id AND [SubId]=@SubId INSERT BULK [TableName] ( [Id] Int , [SubId] Int , [Text] VarChar(max) COLLATE SQL_Latin1_General_CP1_CI_AS ) WITH(CHECK_CONSTRAINTS, FIRE_TRIGGERS) COMMIT TRANSACTION T1 The bulk insert only inserts items matching the Id and SubId of the deletion in the same transaction. Furthermore, these Id and SubId entries should never overlap. When I have enough concurrent transaction of this form, I start to see a significant number of deadlocks between these statements. I added the locking hints XLOCK HOLDLOCK to attempt to deal with the issue, but they don't seem to be helpling. The canonical deadlock graph for this error shows: Connection 1: Holds RangeX-X on PK_TableName Holds IX Page lock on the table Requesting X Page lock on the table Connection 2: Holds IX Page lock on the table Requests RangeX-X lock on the table What do I need to do in order to ensure that these deadlocks don't occur. I have been doing some reading on the RangeX-X locks and I'm not sure I fully understand what is going on with these. Do I have any options short of locking the entire table here?

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• Synchronizing ASP.NET MVC action methods with ReaderWriterLockSlim

  - by James D

  Any obvious issues/problems/gotchas with synchronizing access (in an ASP.NET MVC blogging engine) to a shared object model (NHibernate, but it could be anything) at the Controller/Action level via ReaderWriterLockSlim? (Assume the object model is very large and expensive to build per-request, so we need to share it among requests.) Here's how a typical "Read Post" action would look. Enter the read lock, do some work, exit the read lock. public ActionResult ReadPost(int id) { // ReaderWriterLockSlim allows multiple concurrent writes; this method // only blocks in the unlikely event that some other client is currently // writing to the model, which would only happen if a comment were being // submitted or a new post were being saved. _lock.EnterReadLock(); try { // Access the model, fetch the post with specificied id // Pseudocode, etc. Post p = TheObjectModel.GetPostByID(id); ActionResult ar = View(p); return ar; } finally { // Under all code paths, we must release the read lock _lock.ExitReadLock(); } } Meanwhile, if a user submits a comment or an author authors a new post, they're going to need write access to the model, which is done roughly like so: [AcceptVerbs(HttpVerbs.Post)] public ActionResult SaveComment(/* some posted data */) { // try/finally omitted for brevity _lock.EnterWriteLock(); // Save the comment to the DB, update the model to include the comment, etc. _lock.ExitWriteLock(); } Of course, this could also be done by tagging those action methods with some sort of "synchronized" attribute... but however you do it, my question is is this a bad idea? ps. ReaderWriterLockSlim is optimized for multiple concurrent reads, and only blocks if the write lock is held. Since writes are so infrequent (1000s or 10,000s or 100,000s of reads for every 1 write), and since they're of such a short duration, the effect is that the model is synchronized , and almost nobody ever locks, and if they do, it's not for very long.

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• Lightweight alternative to Manual/AutoResetEvent in C#

  - by sweetlilmre

  Hi, I have written what I hope is a lightweight alternative to using the ManualResetEvent and AutoResetEvent classes in C#/.NET. The reasoning behind this was to have Event like functionality without the weight of using a kernel locking object. Although the code seems to work well in both testing and production, getting this kind of thing right for all possibilities can be a fraught undertaking and I would humbly request any constructive comments and or criticism from the StackOverflow crowd on this. Hopefully (after review) this will be useful to others. Usage should be similar to the Manual/AutoResetEvent classes with Notify() used for Set(). Here goes: using System; using System.Threading; public class Signal { private readonly object _lock = new object(); private readonly bool _autoResetSignal; private bool _notified; public Signal() : this(false, false) { } public Signal(bool initialState, bool autoReset) { _autoResetSignal = autoReset; _notified = initialState; } public virtual void Notify() { lock (_lock) { // first time? if (!_notified) { // set the flag _notified = true; // unblock a thread which is waiting on this signal Monitor.Pulse(_lock); } } } public void Wait() { Wait(Timeout.Infinite); } public virtual bool Wait(int milliseconds) { lock (_lock) { bool ret = true; // this check needs to be inside the lock otherwise you can get nailed // with a race condition where the notify thread sets the flag AFTER // the waiting thread has checked it and acquires the lock and does the // pulse before the Monitor.Wait below - when this happens the caller // will wait forever as he "just missed" the only pulse which is ever // going to happen if (!_notified) { ret = Monitor.Wait(_lock, milliseconds); } if (_autoResetSignal) { _notified = false; } return (ret); } } }

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• In app purchase on iphone.: How to receive your available products *before* someone may be able to b

  - by Thorsten S.

  Currently I am loading my supported products from a plist and after that I send a SKProductsRequest to guarantee that my SKProducts are still valid. So I set up the request, start it and get the response in: (void)productsRequest:(SKProductsRequest *)request didReceiveResponse:(SKProductsResponse *)response Now, so far all functions correctly. Problem: From calling the request until receiving the response it may last several seconds. Until that my app is already loaded and the user may be able to choose and buy a product. But because no products have been received, the available products are not in sync with the validated products - unlikely, but possible error. So my idea is to wait until the data is loaded and only continue when the list is validated. (Just a few seconds waiting...). I have a singleton instance managing all products. + (MyClass *) sharedInstance { if (!sharedInstance) sharedInstance = [MyClass new]; // Now wait until we have our data [condition lock]; while (noEntriesYet) // is yes at begin [condition wait]; [condition unlock]; return sharedInstance; } - productsRequest: didReceiveResponse: { [condition lock]; // I have my data noEntriesYet = false; [condition signal]; [condition unlock]; } Problem: The app freezes. Everything works fine if didReceiveResponse is completed before the sharedInstance is queried. There are different threads, the lock is working if wait is reached during didReceiveResponse, everything fine. But if not, didReceiveResponse is never called even if the request was sent. The lock is released, everything looks ok. I have tried to send the product request in a separate NSThread, with NSOperationQueue...without avail. Why ? What is happening ? How to solve the problem ?

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• How to make a thread that runs at x:00 x:15 x:30 and x:45 do something different at 2:00.

  - by rmarimon

  I have a timer thread that needs to run at a particular moments of the day to do an incremental replication with a database. Right now it runs at the hour, 15 minutes past the hour, 30 minutes past the hour and 45 minutes past the hour. This is the code I have which is working ok: public class TimerRunner implements Runnable { private static final Semaphore lock = new Semaphore(1); private static final ScheduledExecutorService executor = Executors.newSingleThreadScheduledExecutor(); public static void initialize() { long delay = getDelay(); executor.schedule(new TimerRunner(), delay, TimeUnit.SECONDS); } public static void destroy() { executor.shutdownNow(); } private static long getDelay() { Calendar now = Calendar.getInstance(); long p = 15 * 60; // run at 00, 15, 30 and 45 minutes past the hour long second = now.get(Calendar.MINUTE) * 60 + now.get(Calendar.SECOND); return p - (second % p); } public static void replicate() { if (lock.tryAcquire()) { try { Thread t = new Thread(new Runnable() { public void run() { try { // here is where the magic happens } finally { lock.release(); } } }); t.start(); } catch (Exception e) { lock.release(); } } else { throw new IllegalStateException("already running a replicator"); } } public void run() { try { TimerRunner.replicate(); } finally { long delay = getDelay(); executor.schedule(new TimerRunner(), delay, TimeUnit.SECONDS); } } } This process is started by calling TimerRunner.initialize() when a server starts and calling TimerRunner.destroy(). I have created a full replication process (as opposed to incremental) that I would like to run at a certain moment of the day, say 2:00am. How would change the above code to do this? I think that it should be very simple something like if it is now around 2:00am and it's been a long time since I did the full replication then do it now, but I can't get the if right. Beware that sometimes the replicate process takes way longer to complete. Sometimes beyond the 15 minutes, posing a problem in running at around 2:00am.

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• BASH echo write mysql input

  - by jmituzas

  Have a bash menu where variables write to file for mysql input. heres what I have: echo "CREATE DATABASE '$mysqldbn'; #GRANT ALL PRIVILEGES ON *.* TO '$mysqlu'@'$myhost' IDENTIFIED BY '$mysqlup' WITH GRANT OPTION; GRANT SELECT, INSERT, UPDATE, DELETE, CREATE, DROP, INDEX, ALTER, CREATE TEMPORARY TABLES, LOCK TABLES ON '$mysqldbn'.* TO '$mysqlu'@'$myhost' IDENTIFIED BY '$mysqlup'; GRANT SELECT, INSERT, UPDATE, DELETE, CREATE, DROP, INDEX, ALTER, CREATE TEMPORARY TABLES, LOCK TABLES ON '$mysqldbn'.* TO '$mysqlu'@'$myip' IDENTIFIED BY '$mysqlup'; GRANT SELECT, INSERT, UPDATE, DELETE, CREATE, DROP, INDEX, ALTER, CREATE TEMPORARY TABLES, LOCK TABLES ON '$mysqldbn'.* TO '$mysqlu'@'localhost' IDENTIFIED BY '$mysqlup'; GRANT SELECT, INSERT, UPDATE, DELETE, CREATE, DROP, INDEX, ALTER, CREATE TEMPORARY TABLES< LOCK TABLES on '$mysqldbn'.* TO '$mysqlu'@'$rip' IDENTIFIED BY '$mysqlup';" > nmysql.db mysql -u root -p$mypass < nmysql.db problem is to get variables to show I had to put them in single quotes, the single quotes show up as I want for instances like '$mysqlu'@'localhost'. But how can I remove the quotes and still get to use the variable in the instance like, CREATE DATABASE '$mysqldbn' ? Double quotes wont work either, I am at a loss. Thanks in advance, Joe

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• ReaderWriterLockSlim and Pulse/Wait

  - by Jono

  Is there an equivalent of Monitor.Pulse and Monitor.Wait that I can use in conjunction with a ReaderWriterLockSlim? I have a class where I've encapsulated multi-threaded access to an underlying queue. To enqueue something, I acquire a lock that protects the underlying queue (and a couple of other objects) then add the item and Monitor.Pulse the locked object to signal that something was added to the queue. public void Enqueue(ITask task) { lock (mutex) { underlying.Enqueue(task); Monitor.Pulse(mutex); } } On the other end of the queue, I have a single background thread that continuously processes messages as they arrive on the queue. It uses Monitor.Wait when there are no items in the queue, to avoid unnecessary polling. (I consider this to be good design, but any flames (within reason) are welcome if they help me learn otherwise.) private void DequeueForProcessing(object state) { while (true) { ITask task; lock (mutex) { while (underlying.Count == 0) { Monitor.Wait(mutex); } task = underlying.Dequeue(); } Process(task); } } As more operations are added to this class (requiring read-only access to the lock protected underlying), someone suggested using ReaderWriterLockSlim. I've never used the class before, and assuming it can offer some performance benefit, I'm not against it, but only if I can keep the Pulse/Wait design.

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• problem with implementing a simple work queue

  - by John Deerikio

  Hi all, I am having troubles with implementing a simple work queue. Doing some analysis, I am facing a subtle problem. The work queue is backed by a regular linked list. The code looks like this (simplified): 0. while (true) 1. while (enabled == true) 2. acquire lock on the list and get the next action to be executed (blocking operation) (store it in a local variable) 3. execute the action (outside the lock on the list on previous line) 4. get lock on this work queue 5. wait until this work queue has been notified (triggered when setEnabled(true) has been callled) The setEnabled(e) operation looks like this (simplified): enabled = e if (enabled == true) acquire lock on this work queue and do notify() Although this works, there is a condition in which a deadlock occurs. It happens in the following rare situation: while an action is being executed, setEnabled(false) is called just before step (4) is entered, setEnabled(true) is called now step (5) keeps waiting forever, because this work queue has already been notified How do I solve this? I have been looking at this for some time, but I cannot come up with a solution. Please note I am fairly new to thread synchronization. Thanks a lot.

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• Is there a better way to write this repetitive event-declaration code in C# when implementing an int

  - by Damien Wildfire

  I have a lot of code like the following, where I explicitly implement some events required by an interface. public class IMicrowaveNotifier { event EventHandler<EventArgs> DoorClosed; event EventHandler<EventArgs> LightbulbOn; // ... } public class Microwave : IMicrowaveNotifier { private EventHandler<EventArgs> _doorClosed; event EventHandler<EventArgs> IMicrowaveNotifier.DoorClosed { add { lock (this) _doorClosed += value; } remove { lock (this) _doorClosed -= value; } } private EventHandler<EventArgs> _lightbulbOn; event EventHandler<EventArgs> IMicrowaveNotifier.LightbulbOn { add { lock (this) _lightbulbOn += value; } remove { lock (this) _lightbulbOn -= value; } } // ... } You can see that much of this is boilerplate. In Ruby I'd be able to do something like this: class Microwave has_events :door_closed, :lightbulb_on, ... end Is there a similar shorter way of removing this boilerplate in C#? Update: I left a very important part out of my example: namely, the events getting implemented are part of an interface, and I want to implement it explicitly. Sorry for not mentioning this earlier!

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• Does Monitor.Wait ensure that fields are re-read?

  - by Marc Gravell

  It is generally accepted (I believe!) that a lock will force any values from fields to be reloaded (essentially acting as a memory-barrier or fence - my terminology in this area gets a bit loose, I'm afraid), with the consequence that fields that are only ever accessed inside a lock do not themselves need to be volatile. (If I'm wrong already, just say!) A good comment was raised here, questioning whether the same is true if code does a Wait() - i.e. once it has been Pulse()d, will it reload fields from memory, or could they be in a register (etc). Or more simply: does the field need to be volatile to ensure that the current value is obtained when resuming after a Wait()? Looking at reflector, Wait calls down into ObjWait, which is managed internalcall (the same as Enter). The scenario in question was: bool closing; public bool TryDequeue(out T value) { lock (queue) { // arbitrary lock-object (a private readonly ref-type) while (queue.Count == 0) { if (closing) { // <==== (2) access field here value = default(T); return false; } Monitor.Wait(queue); // <==== (1) waits here } ...blah do something with the head of the queue } } Obviously I could just make it volatile, or I could move this out so that I exit and re-enter the Monitor every time it gets pulsed, but I'm intrigued to know if either is necessary.

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