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  • CVE-2009-2260 Information Exposure vulnerability in Stardict

    - by Umang_D
    CVE DescriptionCVSSv2 Base ScoreComponentProduct and Resolution CVE-2009-2260 Information Exposure vulnerability 5.0 Stardict Solaris 11 11/11 SRU 12.4 This notification describes vulnerabilities fixed in third-party components that are included in Oracle's product distributions.Information about vulnerabilities affecting Oracle products can be found on Oracle Critical Patch Updates and Security Alerts page.

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  • CVE-2012-1573 Denial of Service vulnerability in gnutls

    - by Umang_D
    CVE DescriptionCVSSv2 Base ScoreComponentProduct and Resolution CVE-2012-1573 Cryptographic Issues vulnerability 5.0 gnutls Solaris 11 11/11 SRU 12.4 This notification describes vulnerabilities fixed in third-party components that are included in Oracle's product distributions.Information about vulnerabilities affecting Oracle products can be found on Oracle Critical Patch Updates and Security Alerts page.

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  • CVE-2012-3524 Permissions, Privileges, and Access Controls vulnerability in libdbus

    - by Umang_D
    CVE DescriptionCVSSv2 Base ScoreComponentProduct and Resolution CVE-2012-3524 Permissions, Privileges, and Access Controls vulnerability 6.9 libdbus Solaris 11 11/11 SRU 12.4 This notification describes vulnerabilities fixed in third-party components that are included in Oracle's product distributions.Information about vulnerabilities affecting Oracle products can be found on Oracle Critical Patch Updates and Security Alerts page.

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  • CVE-2012-4244 Denial of Service vulnerability in ISC BIND

    - by Umang_D
    CVE DescriptionCVSSv2 Base ScoreComponentProduct and Resolution CVE-2012-4244 Denial of Service vulnerability 7.8 BIND Solaris 11 Contact Support Solaris 10 SPARC : 119783-24 , x86 : 119784-24 Solaris 9 SPARC : 112837-28 , x86 : 114265-27 This notification describes vulnerabilities fixed in third-party components that are included in Oracle's product distributions.Information about vulnerabilities affecting Oracle products can be found on Oracle Critical Patch Updates and Security Alerts page.

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  • Multiple vulnerabilities in PostgreSQL

    - by Umang_D
    CVE DescriptionCVSSv2 Base ScoreComponentProduct and Resolution CVE-2012-3488 Permissions, Privileges, and Access Controls vulnerability 5.8 PostgreSQL Solaris 10 SPARC : 138822-11 , 138824-11 , 138826-11 x86 : 138823-11 , 138825-11 , 138827-11 CVE-2012-3489 Improper Input Validation vulnerability 5.0 This notification describes vulnerabilities fixed in third-party components that are included in Oracle's product distributions.Information about vulnerabilities affecting Oracle products can be found on Oracle Critical Patch Updates and Security Alerts page.

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  • CVE-2011-2728 Denial of Service (DoS) vulnerability in Perl

    - by chandan
    CVE DescriptionCVSSv2 Base ScoreComponentProduct and Resolution CVE-2011-2728 Denial of Service (DoS) vulnerability 4.3 Perl 5.6 Solaris 10 SPARC: 146032-03 X86: 146033-03 Solaris 9 Patches planned but not yet available This notification describes vulnerabilities fixed in third-party components that are included in Oracle's product distributions.Information about vulnerabilities affecting Oracle products can be found on Oracle Critical Patch Updates and Security Alerts page.

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  • Qt 5.2 facilitera fortement le déploiement vers les plateformes Android, avec une automatisation de la création des paquets dans Qt Creator 3.0

    Voici une rapide mise à jour des fonctionnalités prévues pour la sortie de Qt 5.2 pour Android. Cette nouvelle version se concentre sur les premières interactions avec l'écosystème, et les finitions en général. Cela inclut des améliorations sur la prise en charge d'Android par Qt Creator, désormais en version 3.0. La création d'applications Android avec Qt s'en retrouve facilitée. Exemple d'amélioration dans Qt Creator 3.0 : vous recevrez maintenant une notification si le...

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  • CVE-2011-1944 Denial of Service (DoS) vulnerability in libxml2

    - by chandan
    CVE DescriptionCVSSv2 Base ScoreComponentProduct and Resolution CVE-2011-1944 Numeric Errors vulnerability 9.3 libxml2 Solaris 10 SPARC: 125731-07 X86: 125732-07 Solaris 9 Contact Support This notification describes vulnerabilities fixed in third-party components that are included in Sun's product distribution.Information about vulnerabilities affecting Oracle Sun products can be found on Oracle Critical Patch Updates and Security Alerts page.

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  • Multiple vulnerabilities in International Components for Unicode (ICU)

    - by chandan
    CVE DescriptionCVSSv2 Base ScoreComponentProduct and Resolution CVE-2011-2791 Improper Restriction of Operations within the Bounds of a Memory Buffer vulnerability 7.5 International Components for Unicode (ICU) Solaris 10 SPARC: 119810-07 X86: 119811-07 Solaris 11 11/11 SRU 11.4 CVE-2011-4599 Improper Restriction of Operations within the Bounds of a Memory Buffer vulnerability 7.5 This notification describes vulnerabilities fixed in third-party components that are included in Oracle's product distributions.Information about vulnerabilities affecting Oracle products can be found on Oracle Critical Patch Updates and Security Alerts page.

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  • Multiple vulnerabilities in Webmin

    - by RitwikGhoshal
    CVE DescriptionCVSSv2 Base ScoreComponentProduct and Resolution CVE-2012-2981 Improper Input Validation vulnerability 6.0 Webmin Solaris 10 SPARC: 145006-04 X86: 145007-04 CVE-2012-2982 Arbitrary code execution vulnerability 6.5 CVE-2012-2983 Improper Authentication vulnerability 5.0 This notification describes vulnerabilities fixed in third-party components that are included in Oracle's product distributions.Information about vulnerabilities affecting Oracle products can be found on Oracle Critical Patch Updates and Security Alerts page.

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  • CVE-2011-0216 Denial of Service (DoS) vulnerability in libxml2

    - by chandan
    CVE DescriptionCVSSv2 Base ScoreComponentProduct and Resolution CVE-2011-0216 Numeric Errors vulnerability 9.3 libxml2 Solaris 11 Contact Support Solaris 10 SPARC: 125731-07 X86: 125732-07 Solaris 9 Contact Support This notification describes vulnerabilities fixed in third-party components that are included in Sun's product distribution.Information about vulnerabilities affecting Oracle Sun products can be found on Oracle Critical Patch Updates and Security Alerts page.

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  • Cisco PIX to Juniper Netscreen Policy-based VPN fails Phase 2 Proposal

    - by elint
    I've followed the instructions to configure a VPN between a netscreen device and a Cisco PIX as directed by Cisco's [netscreen to PIX VPN]http://www.cisco.com/en/US/tech/tk583/tk372/technologies_configuration_example09186a00801c4445.shtml article. The only differences are that I'm running PIX 6.3(5) and Juniper Netscreen 6.1.0r2.0 (Firewall+VPN). I followed both configurations exactly, and when I try to connect, the Juniper returns with: 2010-02-21 12:54:28 information IKE: Removed Phase 2 SAs after receiving a notification message. 2010-02-21 12:54:28 information IKE pix_public_IP: Received a notification message for DOI 1 14 NO-PROPOSAL-CHOSEN. 2010-02-21 12:54:28 information IKE pix_public_IP Phase 2: Initiated negotiations. On the Netscreen, I've created a Phase 2 Proposal called ToCorpOffice using DH Group#2, 3DES-CBC, and SHA-1, and when configuring the AutoKey IKE, I chose ToCorpOffice and removed all other transforms. I believe I've configured the same on the PIX with: sysopt connection permit-ipsec crypto ipsec transform-set mytrans esp-3des esp-sha-hmac crypto map mymap 10 ipsec-isakmp crypto map mymap 10 match address nonat crypto map mymap 10 set pfs group2 crypto map mymap 10 set peer netscreen_public_ip crypto map mymap 10 set transform-set mytrans crypto map mymap interface outside Saved that and rebooted, so here's the cryptomap info: PIX-FW1# show crypto map Crypto Map: "mymap" interfaces: { outside } Crypto Map "mymap" 10 ipsec-isakmp Peer = netscreen_public_ip access-list nonat; 1 elements access-list nonat line 1 permit ip 192.168.1.0 255.255.255.0 192.168.2.0 255.255.255.0 (hitcnt=0) Current peer: netscreen_public_ip Security association lifetime: 4608000 kilobytes/28800 seconds PFS (Y/N): Y DH group: group2 Transform sets={ mytrans, } PIX-FW1# Any idea why I'm getting a NO-PROPOSAL-CHOSEN error?

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  • How to disable all bounce back email in exim 4.69

    - by liame
    I have set up an email server to send out solicited newsletters. There should be no "regular" users of this server, so it is not desirable to send bounce notifications back to the recipient. Especially so since I am tracking bounces myself by parsing the log files periodically. What I want is to unconditionally prevent exim from ever sending a bounce notification email back to a sender. How can I do this? Thank you! (I accidentally posted this to superuser before posting it here, disregard that if you come across) What I want is an email server that will accept all incoming emails, deliver it accordingly (that is remotely or locally) and not send a bounce notification the sender upon bounce. I log bounces myself, in a database. The only function bounce messages have in my setting is to waste resources and bandwidth. I need to send emails fast, using exiwhat during a run, I see a significant number of deliveries to [email protected]. I could potentially increase my email productivity by 10~20% if all bounce emails are eliminated.

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  • How to completely disable laptop sound?

    - by Alvaro Rodriguez
    I have a HP Pavillion DV7 laptop with win 8 pro. The laptop has an unidentified problem with sound drivers or hardware that sometimes causes volume to constantly jiggle up and down. This is very annoying because of these consequences: Renders mute unusable - as the volume changes the sound unmutes automatically Causes an annoying win 8 "surface UI" notification to appear constantly in the upper left corner, which is distracting enough by itself, but more importantly Renders the whole "surface UI" unusable, because it loses focus whenever the sound changing notification appears When the jiggling happens, the laptop also loses the ability to redirect sound to earphones - sound comes out of the speakers even if earphones are connected. To solve these issues I want to completely disable sound in the laptop (I've tried reinstalling drivers several times to no end). I have tried disabling all sound related drivers and devices in the Device Manager but Windows re-enables those automatically whenever I restart the laptop. The BIOS doesn't have any settings to disable sound hardware either. Please don't suggest having the laptop sound serviced or fixed. It's not worth the expense. I just want to remove sound support so I can use it normally. It is very unusable as it is now.

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  • Emails sent to outlook.com not being delivered

    - by imukcedup
    I'm having an issue that is a little strange. I have a cPanel webserver that I own and have root. I was testing out emailing and noticed some issues. When I send an email to outlook.com address the email sends ok but nothing is recieved at the outlook mailbox. I also dont get an 'email delivery failure notification' in any mailbox. 2014-06-12 09:53:47 SMTP connection from [127.0.0.1]:45334 (TCP/IP connection count = 1) 2014-06-12 09:53:47 1Wv5Rr-0003rA-2K <= [email protected] H=localhost (ourdomain.com) [127.0.0.1]:45334 P=esmtpa A=dovecot_login:joe S=667 [email protected] T="This is a test message" for [email protected] 2014-06-12 09:53:47 SMTP connection from localhost (ourdomain.com) [127.0.0.1]:45334 closed by QUIT 2014-06-12 09:53:50 cwd=/var/spool/MailScanner/incoming/1029481 5 args: /usr/sbin/exim -C /etc/exim_outgoing.conf -Mc 1Wv5Rr-0003rA-2K 2014-06-12 09:53:50 1Wv5Rr-0003rA-2K SMTP connection outbound 1402581230 1Wv5Rr-0003rA-2K ourdomain.com [email protected] 2014-06-12 09:53:50 1Wv5Rr-0003rA-2K => Test Account <[email protected]> R=archive_outgoing_email T=archiver_outgoing 2014-06-12 09:53:52 1Wv5Rr-0003rA-2K => [email protected] R=dkim_lookuphost T=dkim_remote_smtp H=mx1.hotmail.com [65.54.188.110] X=UNKNOWN:AES128-SHA256:128 C="250 <[email protected]> Queued mail for delivery" 2014-06-12 09:53:52 1Wv5Rr-0003rA-2K Completed I have checked the outlook.com's spam folders and its not in there either. This is a new IP address allocation from our ISP and there was a block on gmail addresses, so we know it was used for spam. But with gmail we got a notifaction of failure and I know outlook/microsoft also send out notification. Does anyone know what could be happening here? Thanks

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  • ASP.NET Web API returns 404 for PUT only on some servers

    - by Greg Bacchus
    Ok, I have been racking my brain and the internet for a solution to this. I just can't figure it out. I have written a site that uses ASP.NET MVC Web API and all working nicely until I put it on staging server. The site works fine on my local machine and the dev web server. Both dev and staging servers are Win Server 2008 R2. The problem is this: basically the site works, but there are some API calls that use the HTTP PUT method. These fail on staging returning a 404, but work fine elsewhere. The first problem that I came across and fixed was in Request Filtering. But still getting the 404. I have turned on tracing in IIS and get the following problem. 168. -MODULE_SET_RESPONSE_ERROR_STATUS ModuleName IIS Web Core Notification 16 HttpStatus 404 HttpReason Not Found HttpSubStatus 0 ErrorCode 2147942402 ConfigExceptionInfo Notification MAP_REQUEST_HANDLER ErrorCode The system cannot find the file specified. (0x80070002) The configs are the same on dev and staging, matter of fact the whole site is a direct copy. Why would the GETs and POSTs work, but not the PUTs? Thanks Greg

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  • Incorrect deployment of WSGI app to AWS using Elastic Beanstalk

    - by Dzmitry Zhaleznichenka
    cross-link to AWS forums I have developed a simple Python web service using WSGI and would like to deploy it to AWS cloud using Elastic Beanstalk. My problem is I cannot make all the options I specify in Elastic Beanstalk configuration to be correctly configured in the cloud. For deployment, I use Elastic Beanstalk CLI utility. I have run eb init command and set up the required parameters. After this, a directory named .elasticbeanstalk was created in my source tree. It has two config files that are used for deployment, namely config and optionsettings. The latter one among the other options contains the WSGI configuration that has to update /etc/httpd/conf.d/wsgi.conf at the instances. After some of my adjustments the file has the following settings: [aws:elasticbeanstalk:application:environment] DJANGO_SETTINGS_MODULE = PARAM1 = PARAM2 = PARAM4 = PARAM3 = PARAM5 = [aws:elasticbeanstalk:container:python] WSGIPath = handler.py NumProcesses = 2 StaticFiles = /static= NumThreads = 10 [aws:elasticbeanstalk:container:python:staticfiles] /static = static/ [aws:elasticbeanstalk:hostmanager] LogPublicationControl = false [aws:autoscaling:launchconfiguration] InstanceType = t1.micro EC2KeyName = zmicier-aws [aws:elasticbeanstalk:application] Application Healthcheck URL = [aws:autoscaling:asg] MaxSize = 10 MinSize = 1 Custom Availability Zones = [aws:elasticbeanstalk:monitoring] Automatically Terminate Unhealthy Instances = true [aws:elasticbeanstalk:sns:topics] Notification Endpoint = Notification Protocol = email It turns out that not all of these options are considered when I start the environment or update it. Thus, when I update NumThreads or NumProcesses, the respective parameters get changed in wsgi.conf as expected. But whatever I write to the WSGIPath and StaticFiles parameters, I'm not able to automatically change the respective values of wsgi.conf, they remain Alias /static /opt/python/current/app/ WSGIScriptAlias / /opt/python/current/app/application.py which drives me nuts. Moreover, when I deploy my application using git aws.push and having the following contents of .ebextensions/python.config file, neither of options I specify in it affects the deployment. option_settings: - namespace: aws:elasticbeanstalk:container:python option_name: WSGIPath value: mysite/wsgi.py - namespace: aws:elasticbeanstalk:container:python option_name: NumProcesses value: 5 - namespace: aws:elasticbeanstalk:container:python option_name: NumThreads value: 25 - namespace: aws:elasticbeanstalk:container:python:staticfiles option_name: /static/ value: app/static/ I wonder what I should do to force AWS use all the parameters I specify in the configuration, namely the WSGI Path and path to my static data.

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  • Postfix with relayhost - relay access denied for bounces

    - by Alex
    I have set up a Postfix Mailserver, outgoing mail is being sent through a smarthost/relayhost which requires authentification. That works great, internal clients can send to foreign recipients though this relayhost. However, when an external mail for a local, non-existent user arrives at the server, postfix tries to send a non-delivery notification to the sender. This mail is also sent through the relayhost obviously, but it fails with error 554 5.7.1 : Relay access denied This gets logged to the mail.log: Nov 9 10:26:42 mail postfix/local[5051]: 6568CC1383: to=<[email protected]>, relay=local, delay=0.13, delays=0.02/0.02/0/0.09, dsn=5.1.1, status=bounced (unknown user: "test") Nov 9 10:26:42 mail postfix/cleanup[5045]: 85DF9BFECD: message-id=<[email protected]> Nov 9 10:26:42 mail postfix/qmgr[4912]: 85DF9BFECD: from=<>, size=3066, nrcpt=1 (queue active) Nov 9 10:26:42 mail postfix/bounce[5052]: 6568CC1383: sender non-delivery notification: 85DF9BFECD Nov 9 10:26:42 mail postfix/qmgr[4912]: 6568CC1383: removed Nov 9 10:26:43 mail postfix/smtp[5053]: 85DF9BFECD: to=<[email protected]>, relay=mail.provider.com[168.84.25.111]:587, delay=0.48, delays=0.02/0.01/0.26/0.18, dsn=5.7.1, status=bounced (host mail.provider.com[168.84.25.111] said: 554 5.7.1 <[email protected]>: Relay access denied (in reply to RCPT TO command)) Nov 9 10:26:43 mail postfix/qmgr[4912]: 85DF9BFECD: removed According to this error, I suppose that postfix does not login at the relayhost when sending those bounces. Why? Normal outgoing mail works just fine. This is how my main.cf looks like: http://pastebin.com/Uu1Dryxy And of course /etc/postfix/sasl_password contains the correct credentials for the relayhost. Thanks in advance!

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  • Why does HP Update at remote system trigger RDP printing at local system?

    - by lcbrevard
    This is obscure. When connected with RDP to another system that has HP Update installed on it, either directly running the HP Update or having the notification pop up to ask if you want to run HP Update causes the local system to try to print something to peculiarly-chosen-local-printer. Case 1: Desktop Win 7 Ult system RDP connected to HP Laptop Win 7 Ult system. When HP Update runs on the laptop a dialog for XPS Writer Save As... appears on Desktop system. Even if you put in a name, nothing gets generated and the dialog repeats. And repeats. Until you (a) close the RDP connection and (b) clean out the queued entries. If the HP Update pops up the request to run the update and you are not at the desk when this happens, there can be dozens of queued requests for this bogus printing. NOTE: the XPS Writer is not selected as a default printer on either system. Case 2: (Different) HP Laptop Win 7 Ult system RDP connected to XP Pro "brand X" desktop system but with HP printer drivers installed. If the request to run HP Update notification pops on the XP system, dozens of attempts to print, in this case to a Versa Check Printer driver, are queued. Dismissing the HP request, closing RDP, and cleaning out the queue are required to stop this. NOTE: the Versa Check Writer is not selected as a default printer on either system. THE QUESTION: What the heck is going on here? Some kind of scripting or COM activity that is misdirected?

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  • What should I use to ping multiple IPs and get notified of time outs?

    - by HumanVirus
    I've been using MultiPing to ping hundreds of IPs (from access points and such) and check their performance (packet loss, latency) and uptime. The program is very easy to use, but I was wondering if someone could recommend me something that would work better and that would also work in Linux. The features I'm looking for are: Notification Types: At least desktop notifications and SMS, but it would be great if it also had e-mail, IM, or other types of notifications. (MultiPing has some of these, but they don't work too well.) Being notified about the root problem only: Since some devices are dependent on others, I'd like to be notified only about the root problem. E.g. Let's say I have A[x.x.x.222]B[x.x.x.33C[x.x.x.44]D[x.x.x.55], and B goes down, therefore C and D will also be down. Is it possible to get a notification only about B being down? Light on resources. Ideally multiplatform or at least available for both Linux and Windows. I've heard about Nagios and Shinken being used for monitoring. Would you recommend that I use something of the sort or would that be too much for my needs? If using Nagios, Shinken, or similar software is recommended, can anyone tell me what sites I should go to or what books I should get that would be good for someone who is totally new at this? I'd appreciate any suggestions.

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  • C#/.NET Little Wonders: Interlocked CompareExchange()

    - by James Michael Hare
    Once again, in this series of posts I look at the parts of the .NET Framework that may seem trivial, but can help improve your code by making it easier to write and maintain. The index of all my past little wonders posts can be found here. Two posts ago, I discussed the Interlocked Add(), Increment(), and Decrement() methods (here) for adding and subtracting values in a thread-safe, lightweight manner.  Then, last post I talked about the Interlocked Read() and Exchange() methods (here) for safely and efficiently reading and setting 32 or 64 bit values (or references).  This week, we’ll round out the discussion by talking about the Interlocked CompareExchange() method and how it can be put to use to exchange a value if the current value is what you expected it to be. Dirty reads can lead to bad results Many of the uses of Interlocked that we’ve explored so far have centered around either reading, setting, or adding values.  But what happens if you want to do something more complex such as setting a value based on the previous value in some manner? Perhaps you were creating an application that reads a current balance, applies a deposit, and then saves the new modified balance, where of course you’d want that to happen atomically.  If you read the balance, then go to save the new balance and between that time the previous balance has already changed, you’ll have an issue!  Think about it, if we read the current balance as $400, and we are applying a new deposit of $50.75, but meanwhile someone else deposits $200 and sets the total to $600, but then we write a total of $450.75 we’ve lost $200! Now, certainly for int and long values we can use Interlocked.Add() to handles these cases, and it works well for that.  But what if we want to work with doubles, for example?  Let’s say we wanted to add the numbers from 0 to 99,999 in parallel.  We could do this by spawning several parallel tasks to continuously add to a total: 1: double total = 0; 2:  3: Parallel.For(0, 10000, next => 4: { 5: total += next; 6: }); Were this run on one thread using a standard for loop, we’d expect an answer of 4,999,950,000 (the sum of all numbers from 0 to 99,999).  But when we run this in parallel as written above, we’ll likely get something far off.  The result of one of my runs, for example, was 1,281,880,740.  That is way off!  If this were banking software we’d be in big trouble with our clients.  So what happened?  The += operator is not atomic, it will read in the current value, add the result, then store it back into the total.  At any point in all of this another thread could read a “dirty” current total and accidentally “skip” our add.   So, to clean this up, we could use a lock to guarantee concurrency: 1: double total = 0.0; 2: object locker = new object(); 3:  4: Parallel.For(0, count, next => 5: { 6: lock (locker) 7: { 8: total += next; 9: } 10: }); Which will give us the correct result of 4,999,950,000.  One thing to note is that locking can be heavy, especially if the operation being locked over is trivial, or the life of the lock is a high percentage of the work being performed concurrently.  In the case above, the lock consumes pretty much all of the time of each parallel task – and the task being locked on is relatively trivial. Now, let me put in a disclaimer here before we go further: For most uses, lock is more than sufficient for your needs, and is often the simplest solution!    So, if lock is sufficient for most needs, why would we ever consider another solution?  The problem with locking is that it can suspend execution of your thread while it waits for the signal that the lock is free.  Moreover, if the operation being locked over is trivial, the lock can add a very high level of overhead.  This is why things like Interlocked.Increment() perform so well, instead of locking just to perform an increment, we perform the increment with an atomic, lockless method. As with all things performance related, it’s important to profile before jumping to the conclusion that you should optimize everything in your path.  If your profiling shows that locking is causing a high level of waiting in your application, then it’s time to consider lighter alternatives such as Interlocked. CompareExchange() – Exchange existing value if equal some value So let’s look at how we could use CompareExchange() to solve our problem above.  The general syntax of CompareExchange() is: T CompareExchange<T>(ref T location, T newValue, T expectedValue) If the value in location == expectedValue, then newValue is exchanged.  Either way, the value in location (before exchange) is returned. Actually, CompareExchange() is not one method, but a family of overloaded methods that can take int, long, float, double, pointers, or references.  It cannot take other value types (that is, can’t CompareExchange() two DateTime instances directly).  Also keep in mind that the version that takes any reference type (the generic overload) only checks for reference equality, it does not call any overridden Equals(). So how does this help us?  Well, we can grab the current total, and exchange the new value if total hasn’t changed.  This would look like this: 1: // grab the snapshot 2: double current = total; 3:  4: // if the total hasn’t changed since I grabbed the snapshot, then 5: // set it to the new total 6: Interlocked.CompareExchange(ref total, current + next, current); So what the code above says is: if the amount in total (1st arg) is the same as the amount in current (3rd arg), then set total to current + next (2nd arg).  This check and exchange pair is atomic (and thus thread-safe). This works if total is the same as our snapshot in current, but the problem, is what happens if they aren’t the same?  Well, we know that in either case we will get the previous value of total (before the exchange), back as a result.  Thus, we can test this against our snapshot to see if it was the value we expected: 1: // if the value returned is != current, then our snapshot must be out of date 2: // which means we didn't (and shouldn't) apply current + next 3: if (Interlocked.CompareExchange(ref total, current + next, current) != current) 4: { 5: // ooops, total was not equal to our snapshot in current, what should we do??? 6: } So what do we do if we fail?  That’s up to you and the problem you are trying to solve.  It’s possible you would decide to abort the whole transaction, or perhaps do a lightweight spin and try again.  Let’s try that: 1: double current = total; 2:  3: // make first attempt... 4: if (Interlocked.CompareExchange(ref total, current + i, current) != current) 5: { 6: // if we fail, go into a spin wait, spin, and try again until succeed 7: var spinner = new SpinWait(); 8:  9: do 10: { 11: spinner.SpinOnce(); 12: current = total; 13: } 14: while (Interlocked.CompareExchange(ref total, current + i, current) != current); 15: } 16:  This is not trivial code, but it illustrates a possible use of CompareExchange().  What we are doing is first checking to see if we succeed on the first try, and if so great!  If not, we create a SpinWait and then repeat the process of SpinOnce(), grab a fresh snapshot, and repeat until CompareExchnage() succeeds.  You may wonder why not a simple do-while here, and the reason it’s more efficient to only create the SpinWait until we absolutely know we need one, for optimal efficiency. Though not as simple (or maintainable) as a simple lock, this will perform better in many situations.  Comparing an unlocked (and wrong) version, a version using lock, and the Interlocked of the code, we get the following average times for multiple iterations of adding the sum of 100,000 numbers: 1: Unlocked money average time: 2.1 ms 2: Locked money average time: 5.1 ms 3: Interlocked money average time: 3 ms So the Interlocked.CompareExchange(), while heavier to code, came in lighter than the lock, offering a good compromise of safety and performance when we need to reduce contention. CompareExchange() - it’s not just for adding stuff… So that was one simple use of CompareExchange() in the context of adding double values -- which meant we couldn’t have used the simpler Interlocked.Add() -- but it has other uses as well. If you think about it, this really works anytime you want to create something new based on a current value without using a full lock.  For example, you could use it to create a simple lazy instantiation implementation.  In this case, we want to set the lazy instance only if the previous value was null: 1: public static class Lazy<T> where T : class, new() 2: { 3: private static T _instance; 4:  5: public static T Instance 6: { 7: get 8: { 9: // if current is null, we need to create new instance 10: if (_instance == null) 11: { 12: // attempt create, it will only set if previous was null 13: Interlocked.CompareExchange(ref _instance, new T(), (T)null); 14: } 15:  16: return _instance; 17: } 18: } 19: } So, if _instance == null, this will create a new T() and attempt to exchange it with _instance.  If _instance is not null, then it does nothing and we discard the new T() we created. This is a way to create lazy instances of a type where we are more concerned about locking overhead than creating an accidental duplicate which is not used.  In fact, the BCL implementation of Lazy<T> offers a similar thread-safety choice for Publication thread safety, where it will not guarantee only one instance was created, but it will guarantee that all readers get the same instance.  Another possible use would be in concurrent collections.  Let’s say, for example, that you are creating your own brand new super stack that uses a linked list paradigm and is “lock free”.  We could use Interlocked.CompareExchange() to be able to do a lockless Push() which could be more efficient in multi-threaded applications where several threads are pushing and popping on the stack concurrently. Yes, there are already concurrent collections in the BCL (in .NET 4.0 as part of the TPL), but it’s a fun exercise!  So let’s assume we have a node like this: 1: public sealed class Node<T> 2: { 3: // the data for this node 4: public T Data { get; set; } 5:  6: // the link to the next instance 7: internal Node<T> Next { get; set; } 8: } Then, perhaps, our stack’s Push() operation might look something like: 1: public sealed class SuperStack<T> 2: { 3: private volatile T _head; 4:  5: public void Push(T value) 6: { 7: var newNode = new Node<int> { Data = value, Next = _head }; 8:  9: if (Interlocked.CompareExchange(ref _head, newNode, newNode.Next) != newNode.Next) 10: { 11: var spinner = new SpinWait(); 12:  13: do 14: { 15: spinner.SpinOnce(); 16: newNode.Next = _head; 17: } 18: while (Interlocked.CompareExchange(ref _head, newNode, newNode.Next) != newNode.Next); 19: } 20: } 21:  22: // ... 23: } Notice a similar paradigm here as with adding our doubles before.  What we are doing is creating the new Node with the data to push, and with a Next value being the original node referenced by _head.  This will create our stack behavior (LIFO – Last In, First Out).  Now, we have to set _head to now refer to the newNode, but we must first make sure it hasn’t changed! So we check to see if _head has the same value we saved in our snapshot as newNode.Next, and if so, we set _head to newNode.  This is all done atomically, and the result is _head’s original value, as long as the original value was what we assumed it was with newNode.Next, then we are good and we set it without a lock!  If not, we SpinWait and try again. Once again, this is much lighter than locking in highly parallelized code with lots of contention.  If I compare the method above with a similar class using lock, I get the following results for pushing 100,000 items: 1: Locked SuperStack average time: 6 ms 2: Interlocked SuperStack average time: 4.5 ms So, once again, we can get more efficient than a lock, though there is the cost of added code complexity.  Fortunately for you, most of the concurrent collection you’d ever need are already created for you in the System.Collections.Concurrent (here) namespace – for more information, see my Little Wonders – The Concurent Collections Part 1 (here), Part 2 (here), and Part 3 (here). Summary We’ve seen before how the Interlocked class can be used to safely and efficiently add, increment, decrement, read, and exchange values in a multi-threaded environment.  In addition to these, Interlocked CompareExchange() can be used to perform more complex logic without the need of a lock when lock contention is a concern. The added efficiency, though, comes at the cost of more complex code.  As such, the standard lock is often sufficient for most thread-safety needs.  But if profiling indicates you spend a lot of time waiting for locks, or if you just need a lock for something simple such as an increment, decrement, read, exchange, etc., then consider using the Interlocked class’s methods to reduce wait. Technorati Tags: C#,CSharp,.NET,Little Wonders,Interlocked,CompareExchange,threading,concurrency

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  • Why is Git telling me "Your branch is ahead of 'origin/master' by 11 commits." and how do I get it t

    - by spilth
    I'm a Git newbie. I recently moved a Rails project from Subversion to Git. I followed the tutorial here: http://www.simplisticcomplexity.com/2008/03/05/cleanly-migrate-your-subversion-repository-to-a-git-repository/ I am also using unfuddle.com to store my code. I make changes on my Mac laptop on the train to/from work and then push them to unfuddle when I have a network connection using the following command: git push unfuddle master I use Capistrano for deployments and pull code from the unfuddle repository using the master branch. Lately I've noticed the following message when I run "git status" on my laptop: # On branch master # Your branch is ahead of 'origin/master' by 11 commits. # nothing to commit (working directory clean) And I'm confused as to why. I thought my laptop was the origin... but don't know if either the fact that I originally pulled from Subversion or push to Unfuddle is what's causing the message to show up. How can I: Find out where Git thinks 'origin/master' is? If it's somewhere else, how do I turn my laptop into the 'origin/master'? Get this message to go away. It makes me think Git is unhappy about something. My mac is running Git version 1.6.0.1. When I run git remote show origin as suggested by dbr, I get the following: ~/Projects/GeekFor/geekfor 10:47 AM $ git remote show origin fatal: '/Users/brian/Projects/GeekFor/gf/.git': unable to chdir or not a git archive fatal: The remote end hung up unexpectedly When I run git remote -v as suggested by Aristotle Pagaltzis, I get the following: ~/Projects/GeekFor/geekfor 10:33 AM $ git remote -v origin /Users/brian/Projects/GeekFor/gf/.git unfuddle [email protected]:spilth/geekfor.git Now, interestingly, I'm working on my project in the geekfor directory but it says my origin is my local machine in the gf directory. I believe gf was the temporary directory I used when converting my project from Subversion to Git and probably where I pushed to unfuddle from. Then I believe I checked out a fresh copy from unfuddle to the geekfor directory. So it looks like I should follow dbr's advice and do: git remote rm origin git remote add origin [email protected]:spilth/geekfor.git

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  • UINavigationController + UITableView + UISearchBar + UISplitViewController

    - by ACBurk
    I have an annoying problem. I have an UINavigationController with an UITableView in the Master (Left) pane of my UISplitViewController. When I do normal operations, things push on on to the navigation controller fine. However, when I do a search and push things on, it's like it doesn't account for the space the navigation bar needs. It pushed the new controller on at the very top, then puts the navbar on, overlapping the content! I should add it works fine when doing it in portrait (in the popup menu) and on the iphone. Is this an UISplitViewController bug?

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  • Beginner learning assembly preserving esp after function calls

    - by Daniel
    I'm a beginner learning some assembly, when preserving the ESP register before a function call does it matter if you do it by adding or subtracting? hard to explain, consider the following mov esi, esp sub esp, 12 // on 32bit OS this would mean that there are 3 arguments to the function // push, function call etc cmp esi, esp // should be the same or mov esi, esp // push, function call etc add esp, 12 cmp esi, esp // should be the same Also if for some reason the cmp fails, is it safe to do mov esp, esi to re-align the stack? Thanks EDIT: Also how come i need to do this for a call like sprintf, but MessageBox seems to fix ESP for me? How am i to know what function needs this and what doesn't?

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