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  • In Ruby, how to I read memory values from an external process?

    - by grg-n-sox
    So all I simply want to do is make a Ruby program that reads some values from known memory address in another process's virtual memory. Through my research and basic knowledge of hex editing a running process's x86 assembly in memory, I have found the base address and offsets for the values in memory I want. I do not want to change them; I just want to read them. I asked a developer of a memory editor how to approach this abstract of language and assuming a Windows platform. He told me the Win32API calls for OpenProcess, CreateProcess, ReadProcessMemory, and WriteProcessMemory were the way to go using either C or C++. I think that the way to go would be just using the Win32API class and mapping two instances of it; One for either OpenProcess or CreateProcess, depending on if the user already has th process running or not, and another instance will be mapped to ReadProcessMemory. I probably still need to find the function for getting the list of running processes so I know which running process is the one I want if it is running already. This would take some work to put all together, but I am figuring it wouldn't be too bad to code up. It is just a new area of programming for me since I have never worked this low level from a high level language (well, higher level than C anyways). I am just wondering of the ways to approach this. I could just use a bunch or Win32API calls, but that means having to deal with a bunch of string and array pack and unpacking that is system dependant I want to eventually make this work cross-platform since the process I am reading from is produced from an executable that has multiple platform builds, (I know the memory address changes from system to system. The idea is to have a flat file that contains all memory mappings so the Ruby program can just match the current platform environment to the matching memory mapping.) but from the looks of things I'll just have to make a class that wraps whatever is the current platform's system shared library memory related function calls. For all I know, there could already exist a Ruby gem that takes care of all of this for me that I am just not finding. I could also possibly try editing the executables for each build to make it so whenever the memory values I want to read from are written to by the process, it also writes a copy of the new value to a space in shared memory that I somehow have Ruby make an instance of a class that is a pointer under the hood to that shared memory address and somehow signal to the Ruby program that the value was updated and should be reloaded. Basically a interrupt based system would be nice, but since the purpose of reading these values is just to send to a scoreboard broadcasted from a central server, I could just stick to a polling based system that sends updates at fixed time intervals. I also could just abandon Ruby altogether and go for C or C++ but I do not know those nearly as well. I actually know more x86 than C++ and I only know C as far as system independent ANSI C and have never dealt with shared system libraries before. So is there a gem or lesser known module available that has already done this? If not, then any additional information as to how to accomplish this would be nice. I guess, long story short, how do I do all this? Thanks in advance, Grg PS: Also a confirmation that those Win32API calls should be aimed at the kernel32.dll library would be nice.

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  • NServiceBus Generic Host and mqsvc.exe high CPU

    - by Michael Stephenson
    We have been doing some work with NServiceBus recently and observed some unusual behaviour which was caused by our mistake and seemed worthy of a small post.   The Scenario In our solution we were doing some standard NServiceBus stuff by pushing a message to a queue using NServiceBus.  We had a direct send/receive scenario rather than a publish/subscribe one.   The background process which was meant to collect the message and then process it was a normal NServiceBus message handler.  We would run the NServiceBus.Host.exe which would find the handler and then do the usual NServiceBus magic.   The Problem In this solution we were creating some automated tests around this module of the integration process to ensure that it would work well.  We had two tests.   Test 1 This test would start NServiceBus.Host.exe using the Process object, then seed a message to the queue via our web service façade sitting above the queue which wrapped NServiceBus.  The background process would then process the message and the test would check the message had been processed fine.   If all was well then the NServiceBus.Host.exe process was stopped.   Test 2 In test 2 we would do a very similar thing except that instead of starting the process the test would install NServiceBus.Host.exe as a windows service and then start the service before the test and once the test was executed it would stop the test.   The Results of the Tests Test 1 worked really well, however in test 2 we found that it didn’t really work at all, instead of doing the background process we were finding that between mqsvc.exe and NServiceBus.Host.exe the CPU on the machine was maxed and nothing was really happening.   The Solution After trying a few things we found it was the permissions on the queue were not set correctly.  Once this was resolved it all worked fine and CPU was not excessive and ran just like the console application.   I think the couple of take aways from this are:   Make sure you set the windows service for NserviceBus Generic Host to the right credentials When you install the generic host as a windows service then by default it will use the default windows credentials.  For any production like scenario you should be using a domain account to run the process as via the windows service. Make sure you have the queue set with the right permissions For the credentials you have used to configure the generic host as a windows service you should ensure that this user has the appropriate permissions for any queues it will interact with. Make sure you turn on the right logging configuration in NServiceBus When this wasnt working correctly we didnt know there was an issue, we were just experiencing the high CPU condition.  I am a little surprised that there wasnt something logged and that the process didnt crash.  I guess this could be by design bearing in mind that the process could be monitoring many queues.  In this point Im just saying that originally we didnt have all of the log4net logging which is available from NServiceBus turned on.  Its probably a good idea to have this turned on and configured until you are happy your solution is working fine.   Thanks to Ahmed Hashmi on my team who got this working in the end.

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  • SQL SERVER – Concurrency Basics – Guest Post by Vinod Kumar

    - by pinaldave
    This guest post is by Vinod Kumar. Vinod Kumar has worked with SQL Server extensively since joining the industry over a decade ago. Working on various versions from SQL Server 7.0, Oracle 7.3 and other database technologies – he now works with the Microsoft Technology Center (MTC) as a Technology Architect. Let us read the blog post in Vinod’s own voice. Learning is always fun when it comes to SQL Server and learning the basics again can be more fun. I did write about Transaction Logs and recovery over my blogs and the concept of simplifying the basics is a challenge. In the real world we always see checks and queues for a process – say railway reservation, banks, customer supports etc there is a process of line and queue to facilitate everyone. Shorter the queue higher is the efficiency of system (a.k.a higher is the concurrency). Every database does implement this using checks like locking, blocking mechanisms and they implement the standards in a way to facilitate higher concurrency. In this post, let us talk about the topic of Concurrency and what are the various aspects that one needs to know about concurrency inside SQL Server. Let us learn the concepts as one-liners: Concurrency can be defined as the ability of multiple processes to access or change shared data at the same time. The greater the number of concurrent user processes that can be active without interfering with each other, the greater the concurrency of the database system. Concurrency is reduced when a process that is changing data prevents other processes from reading that data or when a process that is reading data prevents other processes from changing that data. Concurrency is also affected when multiple processes are attempting to change the same data simultaneously. Two approaches to managing concurrent data access: Optimistic Concurrency Model Pessimistic Concurrency Model Concurrency Models Pessimistic Concurrency Default behavior: acquire locks to block access to data that another process is using. Assumes that enough data modification operations are in the system that any given read operation is likely affected by a data modification made by another user (assumes conflicts will occur). Avoids conflicts by acquiring a lock on data being read so no other processes can modify that data. Also acquires locks on data being modified so no other processes can access the data for either reading or modifying. Readers block writer, writers block readers and writers. Optimistic Concurrency Assumes that there are sufficiently few conflicting data modification operations in the system that any single transaction is unlikely to modify data that another transaction is modifying. Default behavior of optimistic concurrency is to use row versioning to allow data readers to see the state of the data before the modification occurs. Older versions of the data are saved so a process reading data can see the data as it was when the process started reading and not affected by any changes being made to that data. Processes modifying the data is unaffected by processes reading the data because the reader is accessing a saved version of the data rows. Readers do not block writers and writers do not block readers, but, writers can and will block writers. Transaction Processing A transaction is the basic unit of work in SQL Server. Transaction consists of SQL commands that read and update the database but the update is not considered final until a COMMIT command is issued (at least for an explicit transaction: marked with a BEGIN TRAN and the end is marked by a COMMIT TRAN or ROLLBACK TRAN). Transactions must exhibit all the ACID properties of a transaction. ACID Properties Transaction processing must guarantee the consistency and recoverability of SQL Server databases. Ensures all transactions are performed as a single unit of work regardless of hardware or system failure. A – Atomicity C – Consistency I – Isolation D- Durability Atomicity: Each transaction is treated as all or nothing – it either commits or aborts. Consistency: ensures that a transaction won’t allow the system to arrive at an incorrect logical state – the data must always be logically correct.  Consistency is honored even in the event of a system failure. Isolation: separates concurrent transactions from the updates of other incomplete transactions. SQL Server accomplishes isolation among transactions by locking data or creating row versions. Durability: After a transaction commits, the durability property ensures that the effects of the transaction persist even if a system failure occurs. If a system failure occurs while a transaction is in progress, the transaction is completely undone, leaving no partial effects on data. Transaction Dependencies In addition to supporting all four ACID properties, a transaction might exhibit few other behaviors (known as dependency problems or consistency problems). Lost Updates: Occur when two processes read the same data and both manipulate the data, changing its value and then both try to update the original data to the new value. The second process might overwrite the first update completely. Dirty Reads: Occurs when a process reads uncommitted data. If one process has changed data but not yet committed the change, another process reading the data will read it in an inconsistent state. Non-repeatable Reads: A read is non-repeatable if a process might get different values when reading the same data in two reads within the same transaction. This can happen when another process changes the data in between the reads that the first process is doing. Phantoms: Occurs when membership in a set changes. It occurs if two SELECT operations using the same predicate in the same transaction return a different number of rows. Isolation Levels SQL Server supports 5 isolation levels that control the behavior of read operations. Read Uncommitted All behaviors except for lost updates are possible. Implemented by allowing the read operations to not take any locks, and because of this, it won’t be blocked by conflicting locks acquired by other processes. The process can read data that another process has modified but not yet committed. When using the read uncommitted isolation level and scanning an entire table, SQL Server can decide to do an allocation order scan (in page-number order) instead of a logical order scan (following page pointers). If another process doing concurrent operations changes data and move rows to a new location in the table, the allocation order scan can end up reading the same row twice. Also can happen if you have read a row before it is updated and then an update moves the row to a higher page number than your scan encounters later. Performing an allocation order scan under Read Uncommitted can cause you to miss a row completely – can happen when a row on a high page number that hasn’t been read yet is updated and moved to a lower page number that has already been read. Read Committed Two varieties of read committed isolation: optimistic and pessimistic (default). Ensures that a read never reads data that another application hasn’t committed. If another transaction is updating data and has exclusive locks on data, your transaction will have to wait for the locks to be released. Your transaction must put share locks on data that are visited, which means that data might be unavailable for others to use. A share lock doesn’t prevent others from reading but prevents them from updating. Read committed (snapshot) ensures that an operation never reads uncommitted data, but not by forcing other processes to wait. SQL Server generates a version of the changed row with its previous committed values. Data being changed is still locked but other processes can see the previous versions of the data as it was before the update operation began. Repeatable Read This is a Pessimistic isolation level. Ensures that if a transaction revisits data or a query is reissued the data doesn’t change. That is, issuing the same query twice within a transaction cannot pickup any changes to data values made by another user’s transaction because no changes can be made by other transactions. However, this does allow phantom rows to appear. Preventing non-repeatable read is a desirable safeguard but cost is that all shared locks in a transaction must be held until the completion of the transaction. Snapshot Snapshot Isolation (SI) is an optimistic isolation level. Allows for processes to read older versions of committed data if the current version is locked. Difference between snapshot and read committed has to do with how old the older versions have to be. It’s possible to have two transactions executing simultaneously that give us a result that is not possible in any serial execution. Serializable This is the strongest of the pessimistic isolation level. Adds to repeatable read isolation level by ensuring that if a query is reissued rows were not added in the interim, i.e, phantoms do not appear. Preventing phantoms is another desirable safeguard, but cost of this extra safeguard is similar to that of repeatable read – all shared locks in a transaction must be held until the transaction completes. In addition serializable isolation level requires that you lock data that has been read but also data that doesn’t exist. Ex: if a SELECT returned no rows, you want it to return no. rows when the query is reissued. This is implemented in SQL Server by a special kind of lock called the key-range lock. Key-range locks require that there be an index on the column that defines the range of values. If there is no index on the column, serializable isolation requires a table lock. Gets its name from the fact that running multiple serializable transactions at the same time is equivalent of running them one at a time. Now that we understand the basics of what concurrency is, the subsequent blog posts will try to bring out the basics around locking, blocking, deadlocks because they are the fundamental blocks that make concurrency possible. Now if you are with me – let us continue learning for SQL Server Locking Basics. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: Concurrency

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  • Why I am not able to display image using swing worker?

    - by Vimal Basdeo
    I was trying some codes to implement a scheduled task and came up with these codes . import java.util.*; class Task extends TimerTask { int count = 1; // run is a abstract method that defines task performed at scheduled time. public void run() { System.out.println(count+" : Mahendra Singh"); count++; } } class TaskScheduling { public static void main(String[] args) { Timer timer = new Timer(); // Schedule to run after every 3 second(3000 millisecond) timer.schedule( new Task(), 3000); } } My output : 1 : Mahendra Singh I expected the compiler to print a series of Mahendra Singh at periodic interval of 3 s but despite waiting for around 15 minutes, I get only one output...How do I solve this out?

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  • With Monit, how do I restart a process when a directory timestamp check fails?

    - by Alterscape
    In my /etc/monit/monitrc I have the following lines: check process foo_server with pidfile /var/run/bwam_server.pid start program = "/Users/foo/foo_server.sh start" stop program = "/Users/foo/foo_server.sh stop" check directory foo_data path "/Users/foo/Library/Application Support/foo_server/data" if timestamp > 1 minute then alert #if timestamp > 1 minute then restart foo_server I know I shouldn't have some of this stuff in my home directory, but this aside: if I uncomment the last line, Monit tells me syntax error on foo_server -- but I am, as far as I understand, correctly defining the process -- how else do I reference it?

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  • Is it possible to interrupt or cancel the trash-delete process?

    - by pete
    I am connected to the company server, onsite not remote, which is Windows based. When, in the OS finder, I go to delete a file or directory that resides on the window-based server, the trash progress panel appears as usual. Not infrequently it will just hang there appearing to be active but no progress occurs on the progress bar. So the X is chosen to stop or cancel the process. A new panel appears, and while appearing to be active, again, just hangs there indefinitely. My lack of reputation prevents posting a screen shot - sorry. The question then is this: Is there a way via the Activity Monitor, Terminal, etc. to interrupt this deleting process in the Mac OS? Currently, I have to force shutdown and reboot to eradicate the ever-deleting panel. Finder relaunch does not solve and only eliminates the finder until I force reboot. Any assistance is appreciated. Thanks, Pete iMac, Mac OS X (10.6.8), i7-2.8ghz, 8gb ram

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  • Why does RunDLL32 process exit early on Windows 7?

    - by Vicky
    On Windows XP and Vista, I can run this code: STARTUPINFO si; PROCESS_INFORMATION pi; BOOL bResult = FALSE; ZeroMemory(&pi, sizeof(pi)); ZeroMemory(&si, sizeof(si)); si.cb = sizeof(STARTUPINFO); si.dwFlags = STARTF_USESHOWWINDOW; si.wShowWindow = SW_SHOW; bResult = CreateProcess(NULL, "rundll32.exe shell32.dll,Control_RunDLL modem.cpl", NULL, NULL, FALSE, NORMAL_PRIORITY_CLASS, NULL, NULL, &si, &pi); if (bResult) { WaitForSingleObject(pi.hProcess, INFINITE); CloseHandle(pi.hProcess); CloseHandle(pi.hThread); } and it operates as I would expect, i.e. the WaitForSingleObject does not return until the Modem Control Panel window has been closed by the user. On Windows 7, the same code, WaitForSingleObject returns straight away (with a return code of 0 indicating that the object signalled the requested state). Similarly, if I take it to the command line, on XP and Vista I can run start /wait rundll32.exe shell32.dll,Control_RunDLL modem.cpl and it does not return control to the command prompt until the Control Panel window is closed, but on Windows 7 it returns immediately. Is this a change in RunDll32? I know MS made some changes to RunDll32 in Windows 7 for UAC, and it looks from these experiments as though one of those changes might have involved spawning an additional process to display the window, and allowing the originating process to exit. The only thing that makes me think this might not be the case is that using a process explorer that shows the creation and destruction of processes, I do not see anything additional being created beyond the called rundll32 process itself. Any other way I can solve this? I just don't want the function to return until the control panel window is closed.

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  • change default port of IIS and let another process to listen on port 80 (Windows Server 2008)

    - by aleroot
    I have an installation of Windows Server 2008 running IIS 6 with a website listening on port 8080, even though I have moved the website to listen on 8080, port 80 is still kept in use by IIS (for truth by the kernel process : System - ProcId : 4). I want to let another process listen on port 80 without uninstalling or disabling IIS, I want to keep IIS listening on port 8080 and another service on port 80, is there a way to do it? I saw another similar thread here on serverfault but the solution (using httpcfg.exe delete iplisten -i 0.0.0.0:80 ) can work only in 2003 because in 2008 the utility httpcfg.exe doesn't exist and it seems that it cannot be installed ... Does anyone have a solution to get rid of the kernel listening on port 80 in Windows Server 2008 with IIS running?

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  • How to troubleshoot down terminal service/CITRIX sessions, when the process just won't terminate?

    - by Chad
    Running a CITRIX presentation server farm, version 4.5.6 on Windows 2003 sp2. In the CITRIX Access Management Console, I sometimes get a session that shows it's in a down state - but has none of the normal info associated with it (user name, applications, client name, idle time, etc...). It does say which servers it's on, so I check out that server's terminal services manager. I can see the down session but cannot reset it. I get: (Error 7024 - the requested operation cannot be completed because the terminal connection is currently busy processing a connect, disconnect, reset, or delete operation.) So I go to the task manager and look up the processes running under that session id. I see it's one of my published apps, but when I try to end the process - it simply does nothing and the process remains. Any way to get rid of these sessions without a server reboot?

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  • Can I recover a nano process from a previous terminal?

    - by davidparks21
    My system crashed while I was in a nano session with unsaved changes. When I log back in via SSH I see the nano process still running when I do a ps. davidparks21@devdb1:/opt/frugg_batch$ ps -ef | grep nano 1001 31714 29481 0 18:32 pts/0 00:00:00 nano frugg_batch_processing 1001 31905 31759 0 19:16 pts/1 00:00:00 grep --color=auto nano davidparks21@devdb1:/opt/frugg_batch$ Is there a way I can bring the nano process back under my control in the new terminal? Or any way to force it to save remotely (from my new terminal)?

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  • After installing VS 2010 - Generic Host Process For Win32 Services problem starts.

    - by Muhammad Kashif Nadeem
    After installing VS 2010 trial I am getting this error "Generic Host Process For Win32 Services Encountered A Problem and needs to close. When this message pops my computer just stuck and I can not even restart it normally. I have found one fix on net but after that fix I can not access my LAN. This fix change these values in registry. HKLM\SYSTEM\CurrentControlSet\Services\netbt\parameters TransportBindName HKLM\Software\Microsoft\OLE EnableDCOM If I revert these registry changes then I again start getting 'Generic Host Process For Win32 Services' I have uninstall VS 2010 but this problem persist. This problem is not because of any virus. Any help to fix this or I have to re install Windows. Thanks.

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  • After installing VS 2010 - Generic Host Process For Win32 Services problem starts.

    - by Muhammad Kashif Nadeem
    After installing VS 2010 trial I am getting this error "Generic Host Process For Win32 Services Encountered A Problem and needs to close. When this message pops my computer just stuck and I can not even restart it normally. I have found one fix on net but after that fix I can not access my LAN. This fix change these values in registry. HKLM\SYSTEM\CurrentControlSet\Services\netbt\parameters TransportBindName HKLM\Software\Microsoft\OLE EnableDCOM If I revert these registry changes then I again start getting 'Generic Host Process For Win32 Services' I have uninstall VS 2010 but this problem persist. This problem is not because of any virus. Any help to fix this or I have to re install Windows. Thanks.

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  • Windows Azure role is state full or not

    - by taimoor-haider
    According to MSDN, an azure service can conatins any number of worker roles. According to my knowledge a worker role can be recycled at any time by Windows Azure Fabric. If it is the true, then: Worker role should be state less OR Worker role should persist its state to Windows Azure storage services. But i want to make a service which conatains client data and do not want to use Azure storage service. How I can accomplish this?

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  • hosting 2 webapps under 1 apache/tomcat

    - by mkoryak
    I am trying to host multiple webapps under tomcat 6 behind apache2 via mod_jk. I am at my wits end with this. the problem i am facing that both domains seems to point to a single tomcat 'domain'. my server.xml looks like this: <Service name="Catalina"> <Connector port="8080" protocol="HTTP/1.1" connectionTimeout="20000" URIEncoding="UTF-8" redirectPort="8443" /> <Connector port="8009" protocol="AJP/1.3" redirectPort="8443" /> <Connector port="8010" protocol="AJP/1.3" redirectPort="8443" /> <Engine name="Catalina" defaultHost="dogself.com"> <Realm className="org.apache.catalina.realm.UserDatabaseRealm" resourceName="UserDatabase"/> <Host name="dogself.com" appBase="webapps-dogself" unpackWARs="true" autoDeploy="true" xmlValidation="false" xmlNamespaceAware="false"> </Host> <Host name="natashacarter.com" appBase="webapps-natashacarter.com" unpackWARs="true" autoDeploy="true" xmlValidation="false" xmlNamespaceAware="false"> </Host> </Engine> </Service> my workers.properties looks like this: worker.list=dogself,natashacarter worker.dogself.port=8009 worker.dogself.host=dogself.com worker.dogself.type=ajp13 worker.natashacarter.port=8010 worker.natashacarter.host=natashacarter.com worker.natashacarter.type=ajp13 finally my apache vhosts look like this: <VirtualHost 69.164.218.75:80> ServerName dogself.com DocumentRoot /srv/www/dogself.com/public_html/ ErrorLog /srv/www/dogself.com/logs/error.log CustomLog /srv/www/dogself.com/logs/access.log combined JkMount /* dogself </VirtualHost> and <VirtualHost 69.164.218.75:80> ServerName natashacarter.com DocumentRoot /srv/www/dogself.com/public_html/ ErrorLog /srv/www/dogself.com/logs/error.log CustomLog /srv/www/dogself.com/logs/access.log combined JkMount /* natashacarter </VirtualHost> when i log into manager webapp on both dogself.com and natashacarter.com, i can deploy to a context path on dogself, and that same contextpath will appear on natashacarter - so i know for a fact that this is the same tomcat domain. edit: just found this in my mod_jk log [Sun Feb 20 21:15:43 2011] [28546:3075521168] [warn] map_uri_to_worker_ext::jk_uri_worker_map.c (962): Uri * is invalid. Uri must start with / [Sun Feb 20 21:16:44 2011] [28548:3075521168] [info] ajp_send_request::jk_ajp_common.c (1496): (dogself) all endpoints are disconnected, detected by connect check (1), cping (0), send (0) but not sure why dogself wouldnt respond please help a brother out

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  • How can I figure out exactly which process is keeping my Mac from going to sleep and waking it up?

    - by pattern86
    I have read this knowledgebase article, but would like to know if there's a way to tell exactly which process is causing my Mac not to follow the sleep schedule I have set in System Preferences Energy Saver. I have narrowed it down to a being a process and will explain why I think so (see below). I am running OS X (10.6.5) on the new iMac 27" and I am certain it's not the following: The "Wake for Network Access" checkbox in Energy Saver settings (has never been a previous issue) Peripherals (has never been a previous issue) Any active GUI application (all are closed) Additional USB/FireWire drives (none are connected) Bluetooth (it's off) Sharing services (has never been a previous issue) The symptoms are as follows: The computer doesn't go to sleep at the predetermined time. It will wake up some number of hours after being put manually to sleep (but not within the first few seconds/minutes.) Is there a specific string I should be looking for in Console? I have tried searching for "wake" and "sleep" but can't make total sense of the results.

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  • How to send Event signal through Processes - C

    - by Jamie Keeling
    Hello all! I have an application consisting of two windows, one communicates to the other and sends it a struct constaining two integers (In this case two rolls of a dice). I will be using events for the following circumstances: Process a sends data to process b, process b displays data Process a closes, in turn closing process b Process b closes a, in turn closing process a I have noticed that if the second process is constantly waiting for the first process to send data then the program will be just sat waiting, which is where the idea of implementing threads on each process occurred and I have started to implement this already. The problem i'm having is that I don't exactly have a lot of experience with threads and events so I'm not sure of the best way to actually implement what I want to do. I'm trying to work out how the other process will know of the event being fired so it can do the tasks it needs to do, I don't understand how one process that is separate from another can tell what the states the events are in especially as it needs to act as soon as the event has changed state. Thanks for any help Edit: I can only use the Create/Set/Open methods for events, sorry for not mentioning it earlier.

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  • What is normal SCSI error handling process (scsi_eh_3) CPU time usage?

    - by Kris Jordan
    Last week I got setup with a new dedicated server that is running 4x SCSI drives in RAID 10 on CentOS. The machine is pretty lightly loaded at the moment and has been running for 8 days. The process 'scsi_eh_3' has a CPU time of 13:09.67 in top. This is 3x the next closest CPU time of 4:03.93 for mysqld. Is it normal for the scsi error handling process to use this much CPU time? (Seems like it goes to 0.3% usage ever 5 seconds.) Could this be an indicator that one or more of the drives is having issues?

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  • JAVA: 500 Worker Threads, what kind of thread pool?

    - by Submerged
    I am wondering if this is the best way to do this. I have about 500 threads that run indefinitely, but Thread.sleep for a minute when done one cycle of processing. ExecutorService es = Executors.newFixedThreadPool(list.size()+1); for (int i = 0; i < list.size(); i++) { es.execute(coreAppVector.elementAt(i)); //coreAppVector is a vector of extends thread objects } I do need a separate threads for each running task, so changing the architecture isn't an option. I tried making my threadPool size equal to Runtime.getRuntime().availableProcessors() which attempted to run all 500 threads, but only let 8 (4xhyperthreading) of them execute. The other threads wouldn't surrender and let other threads have their turn. I tried putting in a wait() and notify(), but still no luck. If anyone has a simple example or some tips, I would be grateful!

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  • How to get the pid of a running process using a single command that parse the output of ps?

    - by Sorin Sbarnea
    I am looking for a single line that does return the pid of a running process. Currently I have: ps -A -o pid,cmd|grep xxx|head -n 1 And this returns the fist pid, command. I need only the first number from the output and ignore the rest. I suppose sed or awk would help here but my experience with them is limited. Also, this has another problem, it will return the pid of grep if the xxx is not running. It's really important to have a single line, as I want to reuse the output for doing something else, like killing that process.

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  • Does waitpid yield valid status information for a child process that has already exited?

    - by dtrebbien
    If I fork a child process, and the child process exits before the parent even calls waitpid, then is the exit status information that is set by waitpid still valid? If so, when does it become not valid; i.e., how do I ensure that I can call waitpid on the child pid and continue to get valid exit status information after an arbitrary amount of time, and how do I "clean up" (tell the OS that I am no longer interested in the exit status information for the finished child process)? I was playing around with the following code, and it appears that the exit status information is valid for at least a few seconds after the child finishes, but I do not know for how long or how to inform the OS that I won't be calling waitpid again: #include <assert.h> #include <pthread.h> #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <sys/wait.h> int main() { pid_t pid = fork(); if (pid < 0) { fprintf(stderr, "Failed to fork\n"); return EXIT_FAILURE; } else if (pid == 0) { // code for child process _exit(17); } else { // code for parent sleep(3); int status; waitpid(pid, &status, 0); waitpid(pid, &status, 0); // call `waitpid` again just to see if the first call had an effect assert(WIFEXITED(status)); assert(WEXITSTATUS(status) == 17); } return EXIT_SUCCESS; }

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  • How to properly handle signals when using the worker thread pattern?

    - by ipartola
    I have a simple server that looks something like this: void *run_thread(void *arg) { // Communicate via a blocking socket } int main() { // Initialization happens here... // Main event loop while (1) { new_client = accept(socket, ...); pthread_create(&thread, NULL, &run_thread, *thread_data*); pthread_detach(thread); } // Do cleanup stuff: close(socket); // Wait for existing threads to finish exit(0); ) Thus when a SIGINT or SIGTERM is received I need to break out of the main event loop to get to the clean up code. Moreover most likely the master thread is waiting on the accept() call so it's not able to check some other variable to see if it should break;. Most of the advice I found was along the lines of this: http://devcry.blogspot.com/2009/05/pthreads-and-unix-signals.html (creating a special signal handling thread to catch all the signals and do processing on those). However, it's the processing portion that I can't really wrap my head around: how can I possibly tell the main thread to return from the accept() call and check on an external variable to see if it should break;?

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