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  • How to lock non-browser clients from submitting a request?

    - by Thomas Kohl
    I want to block non-browser clients from accessing certain pages / successfully making a request. The website content is served to authenticated users. What happens is that our user gives his credentials to our website to 3rd party - it can be another website or a mobile application - that performs requests on his behalf. Say there is a form that the user fills out and sends a message. Can I protect this form so that the server processing the submission can tell whether the user has submitted it directly from the browser or not? I don't want to use CAPTCHA for usability reasons. Can I do it with some javascript?

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  • MySQL locking problem

    - by teehoo
    I have a simple setup of a set of writers and a set of readers working with a MySQL ISAM table. The writers are only inserting rows while the readers are only checking for new rows. OK, so I know that I don't need a lock in this situation, since I'm not modifying existing rows. However my Writers are accessing one more table that does need a lock. I piece of information seems irrelevant except for the following limitation stated in the MySQL documentation: A session that requires locks must acquire all the locks that it needs in a single LOCK TABLES statement. While the locks thus obtained are held, the session can access only the locked tables. For example, in the following sequence of statements, an error occurs for the attempt to access t2 because it was not locked in the LOCK TABLES statement: So to access the table I want to insert rows into, I NEED to lock it, which is causing me performance problems. Any suggestions of how to get around this?

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  • How to lock the Screen customly? Just like WaveSecure in Android

    - by HackNone
    I want to do a demo just like WaveSecure, which win Android Develop Challenge 2 with a third place. Now I have a problem in locking the screen customly, so I want to know how WaveSecure achieve its locking function, as the following picture show: http://goo.gl/XlPP When the mobile is locked, WaveSecure can require customer to input their own password. So I think WaveSecure must replace Android's original locking function. And I also google it, but I didn't find anything helpful. I only find two packages may be helpful. They are: android.app.KeyguardManager android.os.PowerManager But after I reading the Android Docs, I still can't have an idea on it. Can you help me? Thx:)

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  • Outlook 2010 - HTML Images not downloaded - at all - by default

    - by Scott Lock
    Maybe it's just me but I found this "Security Feature" of Office 2010 a bit annyoing out of the box.  Outlook does not download any pictures by default for HTML emails.  Now this is nothing new, but what is different is that Outlook 2010 has added another layer of security around the pictures.  You now have the option to finely tune when things are downloaded.  The side affect is that nothing is downloaded at all.  And when I would click on "Download Images" on an email, it still would not show the images.  I found that I had to explicitly tell Outlook to download HTML images and then restart Windows.  It did not work if I simply restarted Office.  Again, maybe this was just me.  Here's what you need to do in Outlook 2010 to enable images for HTML: Click on the new "File" tab Click on "Options" Click on "Trust Center" Clicn on "Trust Center Settings" Uncheck the "Don't download pictures automatically in HTML e-mail messages or RSS items" check box Click the "Okay" button Exit Outlook 2010 Again, for me I had to restart Windows (Windows 7 64bit, Office 2010 64bit) to get this to "take affect".

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  • How do you lock down & secure files stored on server in ASP.NET?

    - by Jon
    How do I go about securing files that are stored on the server? We have an ASP.NET app which generates PDFs. These are not stored in the wwwroot folder but in another folder i.e. C:\inetpub\data. This provides more security but maybe not enough. The ASP.NET/IIS process will need write access to this folder so it generate the PDFs there. Once the pdf is generated, it can be viewed using an ASP.NET form called viewpdf.aspx with the file to be viewed add to the query string like so viewpdf.aspx?FILE=mynewfile.pdf. This is loaded from a gridview. The full path to C:\inetpub\data is resolved and loaded in the Page_load event of the viewer page. Now I'm wondering how to secure this. Anybody could just view the file. Not by entering in the URL, as it won't been seen by IIS (its not in wwwroot), but could change the querystring in the viewpdf page. How do I stop anybody hacking this?

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  • SQL Compact Edition 3.5 SP 1 - LockTimeOutException - how to debug?

    - by Bob King
    Intermittently in our app, we encounter LockTimeoutExceptions being throw from SQL CE. We've recently upgraded to 3.5 SP 1, and a number of them seem to have gone away, but we still do see them occasionally. I'm certain it's a bug in our code (which is multi-threaded) but I haven't been able to pin it down precisely. Does anyone have any good techniques for debugging this problem? The exceptions log like this (there's never a stack trace for these exceptions): SQL Server Compact timed out waiting for a lock. The default lock time is 2000ms for devices and 5000ms for desktops. The default lock timeout can be increased in the connection string using the ssce: default lock timeout property. [ Session id = 6,Thread id = 7856,Process id = 10116,Table name = Product,Conflict type = s lock (x blocks),Resource = DDL ] Our database is read-heavy, but does seldom writes, and I think I've got everything protected where it needs to be. EDIT: SQL CE already automatically uses NOLOCK http://msdn.microsoft.com/en-us/library/ms172398(sql.90).aspx

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  • Do Managers in Python Multiprocessing module lock the shared data?

    - by AnonProcess
    This Question has been asked before: http://stackoverflow.com/questions/2936626/how-to-share-a-dictionary-between-multiple-processes-in-python-without-locking However I have several doubts regarding the program given in the answer: The issue is that the following step isn't atomic d['blah'] += 1 Even with locking the answer provided in that question would lead to random results. Since Process 1 read value of d['blah'] saves it on the stack increments it and again writes it. In Between a Process 2 can read the d['blah'] as well. Locking means that while d['blah'] is being written or read no other process can access it. Can someone clarify my doubts?

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  • (Windows) How to lock all applications (explorer, task manager etc.) and make only the browser activ

    - by Unni
    I'm trying to run only the browser in the system - locking access to everything else. Only the supervisor can resume the normal functioning of the system after giving a password. This kind of activity is usually done by virus. Disabling the registry for Task manager etc. Does anyone know of any source available that does this? I might be able to pull it off in Windows XP. But have anyone tried this in Windows 7 ? The aim is to to emulate the Chrome OS on Windows. Only the browser. Nothing else.

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  • How to get a green to show up like the charging battery on the iPhone lock screen?

    - by tarheel
    I am trying to get a color to show up on screen just like the charging battery (shown here): After looking at the Apple Documentation on UIColor here, I have attempted using both colorWithHue:saturation:brightness:aplha: and colorWithRed:green:blue:alpha: to get a color to show up like that. For example when I use colorWithHue:.3 saturation:.84 brightness:1 alpha:.5 on a black background, it renders a color like this: or the colorWithRed:0 green:1 blue:0 alpha:.5 on a black background shows up like this: It doesn't have that translucent or glossy look to it. Is there a better method to use? Or do I just not have the values right? (I have tried many combinations)

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  • .net- open excel file, format the file and save

    - by Lock
    I have an ASP web service that uses the Crystal Reports API to download an Excel report. Now, there is a few things I do not like about the Excel report that Crystal generates: - The column widths are static (as in they are not adjusted for the content). - I can't format the header row to be bold - If I suppress a data column in the report, it comes out in the Excel spreadsheet as a blank column. I currently use PHP to open the excel file, autosize the columns, bold the heading and remove blank columns, although using the PHPExcel class for this doesn't work well when the spreadsheet is only a few 100kb in size. I am thinking if I move this activity into the .NET web service, the performance will be much better. Does anyone know an efficient way of opening a Excel file and performing the operations listed above?

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  • SEO for duplicate sites with multiple domain extensions

    - by lock
    I am running business in different nations and I got domains for example www.mydomain.com www.mydomain.us www.mydomain.ca www.mydomain.uk www.mydomain.com.au So, if I run same website with same content (of course there will be little changes like address, etc.) as all these domains has same content will it be considered as spam or will the domains rank well as per the country? Also, is there solutions if Google considers this as spam.

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  • Subtle C++ mistake, can you spot it?

    - by aaa
    I ran into a subtle C++ gotcha, took me while to resolve it. Can you spot it? class synchronized_container { boost::mutex mutex_; std::vector <T> container_; void push_back(const T &value) { boost::scoped_lock(mutex_); // raii mutex lock container_.push_back(value); } ... }; scoped lock is a raii mutex lock, obtains lock on constructor, release lock in destructor. The program will work as expected in serial, but will may occasionally produce weird stuff with more than one thread.

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  • Why is there a /etc/init.d/mysql file on this Slackware machine? How could it have gotten there?

    - by jasonspiro
    A client of my IT-consulting service owns a web-development shop. He's been having problems with a Slackware 12.0 server running MySQL 5.0.67. The machine was set up by the client's sysadmin, who left on bad terms. My client no longer employs a sysadmin. As far as I can tell, the only copy of MySQL that's installed is the one described in /var/log/packages/mysql-5.0.67-i486-1: PACKAGE NAME: mysql-5.0.67-i486-1 COMPRESSED PACKAGE SIZE: 16828 K UNCOMPRESSED PACKAGE SIZE: 33840 K PACKAGE LOCATION: /var/slapt-get/archives/./slackware/ap/mysql-5.0.67-i486-1.tgz PACKAGE DESCRIPTION: mysql: mysql (SQL-based relational database server) mysql: mysql: MySQL is a fast, multi-threaded, multi-user, and robust SQL mysql: (Structured Query Language) database server. It comes with a nice API mysql: which makes it easy to integrate into other applications. mysql: mysql: The home page for MySQL is http://www.mysql.com/ mysql: mysql: mysql: mysql: FILE LIST: ./ var/ var/lib/ var/lib/mysql/ var/run/ var/run/mysql/ install/ install/doinst.sh install/slack-desc usr/ usr/include/ usr/include/mysql/ usr/include/mysql/my_alloc.h usr/include/mysql/sql_common.h usr/include/mysql/my_dbug.h usr/include/mysql/errmsg.h usr/include/mysql/my_pthread.h usr/include/mysql/my_list.h usr/include/mysql/mysql.h usr/include/mysql/sslopt-vars.h usr/include/mysql/my_config.h usr/include/mysql/mysql_com.h usr/include/mysql/m_string.h usr/include/mysql/sslopt-case.h usr/include/mysql/my_xml.h usr/include/mysql/sql_state.h usr/include/mysql/my_global.h usr/include/mysql/my_sys.h usr/include/mysql/mysqld_ername.h usr/include/mysql/mysqld_error.h usr/include/mysql/sslopt-longopts.h usr/include/mysql/keycache.h usr/include/mysql/my_net.h usr/include/mysql/mysql_version.h usr/include/mysql/my_no_pthread.h usr/include/mysql/decimal.h usr/include/mysql/readline.h usr/include/mysql/my_attribute.h usr/include/mysql/typelib.h usr/include/mysql/my_dir.h usr/include/mysql/raid.h usr/include/mysql/m_ctype.h usr/include/mysql/mysql_embed.h usr/include/mysql/mysql_time.h usr/include/mysql/my_getopt.h usr/lib/ usr/lib/mysql/ usr/lib/mysql/libmysqlclient_r.so.15.0.0 usr/lib/mysql/libmysqlclient_r.la usr/lib/mysql/libmyisammrg.a usr/lib/mysql/libmystrings.a usr/lib/mysql/libmyisam.a usr/lib/mysql/libmysqlclient.so.15.0.0 usr/lib/mysql/libmysqlclient_r.a usr/lib/mysql/libmysqlclient.a usr/lib/mysql/libheap.a usr/lib/mysql/libvio.a usr/lib/mysql/libmysqlclient.la usr/lib/mysql/libmysys.a usr/lib/mysql/libdbug.a usr/bin/ usr/bin/comp_err usr/bin/my_print_defaults usr/bin/resolve_stack_dump usr/bin/msql2mysql usr/bin/mysqltestmanager-pwgen usr/bin/myisampack usr/bin/replace usr/bin/mysqld_multi usr/bin/mysqlaccess usr/bin/mysql_install_db usr/bin/innochecksum usr/bin/myisam_ftdump usr/bin/mysqlcheck usr/bin/mysqltest usr/bin/mysql_upgrade_shell usr/bin/mysql_secure_installation usr/bin/mysql_fix_extensions usr/bin/mysqld_safe usr/bin/mysql_explain_log usr/bin/mysqlimport usr/bin/myisamlog usr/bin/mysql_tzinfo_to_sql usr/bin/mysql_upgrade usr/bin/mysqltestmanager usr/bin/mysql_fix_privilege_tables usr/bin/mysql_find_rows usr/bin/mysql_convert_table_format usr/bin/mysqltestmanagerc usr/bin/mysqlhotcopy usr/bin/mysqldump usr/bin/mysqlshow usr/bin/mysqlbug usr/bin/mysql_config usr/bin/mysqldumpslow usr/bin/mysql_waitpid usr/bin/mysqlbinlog usr/bin/mysql_client_test usr/bin/perror usr/bin/mysql usr/bin/myisamchk usr/bin/mysql_setpermission usr/bin/mysqladmin usr/bin/mysql_zap usr/bin/mysql_tableinfo usr/bin/resolveip usr/share/ usr/share/mysql/ usr/share/mysql/errmsg.txt usr/share/mysql/swedish/ usr/share/mysql/swedish/errmsg.sys usr/share/mysql/mysql_system_tables_data.sql usr/share/mysql/mysql.server usr/share/mysql/hungarian/ usr/share/mysql/hungarian/errmsg.sys usr/share/mysql/norwegian/ usr/share/mysql/norwegian/errmsg.sys usr/share/mysql/slovak/ usr/share/mysql/slovak/errmsg.sys usr/share/mysql/spanish/ usr/share/mysql/spanish/errmsg.sys usr/share/mysql/polish/ usr/share/mysql/polish/errmsg.sys usr/share/mysql/ukrainian/ usr/share/mysql/ukrainian/errmsg.sys usr/share/mysql/danish/ usr/share/mysql/danish/errmsg.sys usr/share/mysql/romanian/ usr/share/mysql/romanian/errmsg.sys usr/share/mysql/english/ usr/share/mysql/english/errmsg.sys usr/share/mysql/charsets/ usr/share/mysql/charsets/latin2.xml usr/share/mysql/charsets/greek.xml usr/share/mysql/charsets/koi8r.xml usr/share/mysql/charsets/latin1.xml usr/share/mysql/charsets/cp866.xml usr/share/mysql/charsets/geostd8.xml usr/share/mysql/charsets/cp1250.xml usr/share/mysql/charsets/koi8u.xml usr/share/mysql/charsets/cp852.xml usr/share/mysql/charsets/hebrew.xml usr/share/mysql/charsets/latin7.xml usr/share/mysql/charsets/README usr/share/mysql/charsets/ascii.xml usr/share/mysql/charsets/cp1251.xml usr/share/mysql/charsets/macce.xml usr/share/mysql/charsets/latin5.xml usr/share/mysql/charsets/Index.xml usr/share/mysql/charsets/macroman.xml usr/share/mysql/charsets/cp1256.xml usr/share/mysql/charsets/keybcs2.xml usr/share/mysql/charsets/swe7.xml usr/share/mysql/charsets/armscii8.xml usr/share/mysql/charsets/dec8.xml usr/share/mysql/charsets/cp1257.xml usr/share/mysql/charsets/hp8.xml usr/share/mysql/charsets/cp850.xml usr/share/mysql/korean/ usr/share/mysql/korean/errmsg.sys usr/share/mysql/german/ usr/share/mysql/german/errmsg.sys usr/share/mysql/mi_test_all.res usr/share/mysql/greek/ usr/share/mysql/greek/errmsg.sys usr/share/mysql/french/ usr/share/mysql/french/errmsg.sys usr/share/mysql/mysql_fix_privilege_tables.sql usr/share/mysql/dutch/ usr/share/mysql/dutch/errmsg.sys usr/share/mysql/serbian/ usr/share/mysql/serbian/errmsg.sys usr/share/mysql/mysql_system_tables.sql usr/share/mysql/my-huge.cnf usr/share/mysql/portuguese/ usr/share/mysql/portuguese/errmsg.sys usr/share/mysql/japanese/ usr/share/mysql/japanese/errmsg.sys usr/share/mysql/mysql_test_data_timezone.sql usr/share/mysql/russian/ usr/share/mysql/russian/errmsg.sys usr/share/mysql/czech/ usr/share/mysql/czech/errmsg.sys usr/share/mysql/fill_help_tables.sql usr/share/mysql/estonian/ usr/share/mysql/estonian/errmsg.sys usr/share/mysql/my-medium.cnf usr/share/mysql/norwegian-ny/ usr/share/mysql/norwegian-ny/errmsg.sys usr/share/mysql/my-small.cnf usr/share/mysql/mysql-log-rotate usr/share/mysql/italian/ usr/share/mysql/italian/errmsg.sys usr/share/mysql/my-large.cnf usr/share/mysql/ndb-config-2-node.ini usr/share/mysql/binary-configure usr/share/mysql/mi_test_all usr/share/mysql/mysqld_multi.server usr/share/mysql/my-innodb-heavy-4G.cnf usr/doc/ usr/doc/mysql-5.0.67/ usr/doc/mysql-5.0.67/README usr/doc/mysql-5.0.67/Docs/ usr/doc/mysql-5.0.67/Docs/INSTALL-BINARY usr/doc/mysql-5.0.67/COPYING usr/info/ usr/info/mysql.info.gz usr/libexec/ usr/libexec/mysqld usr/libexec/mysqlmanager usr/man/ usr/man/man8/ usr/man/man8/mysqlmanager.8.gz usr/man/man8/mysqld.8.gz usr/man/man1/ usr/man/man1/mysql_zap.1.gz usr/man/man1/mysql_setpermission.1.gz usr/man/man1/mysql_tzinfo_to_sql.1.gz usr/man/man1/msql2mysql.1.gz usr/man/man1/mysql_tableinfo.1.gz usr/man/man1/mysql_explain_log.1.gz usr/man/man1/mysqlcheck.1.gz usr/man/man1/comp_err.1.gz usr/man/man1/my_print_defaults.1.gz usr/man/man1/mysqlbinlog.1.gz usr/man/man1/myisam_ftdump.1.gz usr/man/man1/mysql_upgrade.1.gz usr/man/man1/mysql.1.gz usr/man/man1/mysql_client_test.1.gz usr/man/man1/resolve_stack_dump.1.gz usr/man/man1/mysql_fix_extensions.1.gz usr/man/man1/mysqlmanagerc.1.gz usr/man/man1/mysql_config.1.gz usr/man/man1/mysqlshow.1.gz usr/man/man1/myisamlog.1.gz usr/man/man1/replace.1.gz usr/man/man1/mysqlmanager-pwgen.1.gz usr/man/man1/mysqltest.1.gz usr/man/man1/innochecksum.1.gz usr/man/man1/mysqladmin.1.gz usr/man/man1/perror.1.gz usr/man/man1/mysql_waitpid.1.gz usr/man/man1/mysql_convert_table_format.1.gz usr/man/man1/mysqlman.1.gz usr/man/man1/mysqlimport.1.gz usr/man/man1/mysqlbug.1.gz usr/man/man1/mysql_find_rows.1.gz usr/man/man1/myisampack.1.gz usr/man/man1/myisamchk.1.gz usr/man/man1/mysql_fix_privilege_tables.1.gz usr/man/man1/mysql-stress-test.pl.1.gz usr/man/man1/resolveip.1.gz usr/man/man1/make_win_bin_dist.1.gz usr/man/man1/mysqlhotcopy.1.gz usr/man/man1/mysqld_multi.1.gz usr/man/man1/safe_mysqld.1.gz usr/man/man1/mysql_secure_installation.1.gz usr/man/man1/mysql_install_db.1.gz usr/man/man1/mysqldump.1.gz usr/man/man1/mysql-test-run.pl.1.gz usr/man/man1/mysqld_safe.1.gz usr/man/man1/mysqlaccess.1.gz usr/man/man1/mysql.server.1.gz usr/man/man1/make_win_src_distribution.1.gz etc/ etc/rc.d/ etc/rc.d/rc.mysqld.new etc/my-huge.cnf etc/my-medium.cnf etc/my-small.cnf etc/my-large.cnf /etc/rc.d/rc.mysqld is an ordinary Slackware-type start/stop script: #!/bin/sh # Start/stop/restart mysqld. # # Copyright 2003 Patrick J. Volkerding, Concord, CA # Copyright 2003 Slackware Linux, Inc., Concord, CA # # This program comes with NO WARRANTY, to the extent permitted by law. # You may redistribute copies of this program under the terms of the # GNU General Public License. # To start MySQL automatically at boot, be sure this script is executable: # chmod 755 /etc/rc.d/rc.mysqld # Before you can run MySQL, you must have a database. To install an initial # database, do this as root: # # su - mysql # mysql_install_db # # Note that step one is becoming the mysql user. It's important to do this # before making any changes to the database, or mysqld won't be able to write # to it later (this can be fixed with 'chown -R mysql.mysql /var/lib/mysql'). # To allow outside connections to the database comment out the next line. # If you don't need incoming network connections, then leave the line # uncommented to improve system security. #SKIP="--skip-networking" # Start mysqld: mysqld_start() { if [ -x /usr/bin/mysqld_safe ]; then # If there is an old PID file (no mysqld running), clean it up: if [ -r /var/run/mysql/mysql.pid ]; then if ! ps axc | grep mysqld 1> /dev/null 2> /dev/null ; then echo "Cleaning up old /var/run/mysql/mysql.pid." rm -f /var/run/mysql/mysql.pid fi fi /usr/bin/mysqld_safe --datadir=/var/lib/mysql --pid-file=/var/run/mysql/mysql.pid $SKIP & fi } # Stop mysqld: mysqld_stop() { # If there is no PID file, ignore this request... if [ -r /var/run/mysql/mysql.pid ]; then killall mysqld # Wait at least one minute for it to exit, as we don't know how big the DB is... for second in 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 \ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 60 ; do if [ ! -r /var/run/mysql/mysql.pid ]; then break; fi sleep 1 done if [ "$second" = "60" ]; then echo "WARNING: Gave up waiting for mysqld to exit!" sleep 15 fi fi } # Restart mysqld: mysqld_restart() { mysqld_stop mysqld_start } case "$1" in 'start') mysqld_start ;; 'stop') mysqld_stop ;; 'restart') mysqld_restart ;; *) echo "usage $0 start|stop|restart" esac But there's also an unexpected init script on the machine, named /etc/init.d/mysql: #!/bin/sh # Copyright Abandoned 1996 TCX DataKonsult AB & Monty Program KB & Detron HB # This file is public domain and comes with NO WARRANTY of any kind # MySQL daemon start/stop script. # Usually this is put in /etc/init.d (at least on machines SYSV R4 based # systems) and linked to /etc/rc3.d/S99mysql and /etc/rc0.d/K01mysql. # When this is done the mysql server will be started when the machine is # started and shut down when the systems goes down. # Comments to support chkconfig on RedHat Linux # chkconfig: 2345 64 36 # description: A very fast and reliable SQL database engine. # Comments to support LSB init script conventions ### BEGIN INIT INFO # Provides: mysql # Required-Start: $local_fs $network $remote_fs # Should-Start: ypbind nscd ldap ntpd xntpd # Required-Stop: $local_fs $network $remote_fs # Default-Start: 2 3 4 5 # Default-Stop: 0 1 6 # Short-Description: start and stop MySQL # Description: MySQL is a very fast and reliable SQL database engine. ### END INIT INFO # If you install MySQL on some other places than /usr, then you # have to do one of the following things for this script to work: # # - Run this script from within the MySQL installation directory # - Create a /etc/my.cnf file with the following information: # [mysqld] # basedir=<path-to-mysql-installation-directory> # - Add the above to any other configuration file (for example ~/.my.ini) # and copy my_print_defaults to /usr/bin # - Add the path to the mysql-installation-directory to the basedir variable # below. # # If you want to affect other MySQL variables, you should make your changes # in the /etc/my.cnf, ~/.my.cnf or other MySQL configuration files. # If you change base dir, you must also change datadir. These may get # overwritten by settings in the MySQL configuration files. #basedir= #datadir= # Default value, in seconds, afterwhich the script should timeout waiting # for server start. # Value here is overriden by value in my.cnf. # 0 means don't wait at all # Negative numbers mean to wait indefinitely service_startup_timeout=900 # The following variables are only set for letting mysql.server find things. # Set some defaults pid_file=/var/run/mysql/mysql.pid server_pid_file=/var/run/mysql/mysql.pid use_mysqld_safe=1 user=mysql if test -z "$basedir" then basedir=/usr bindir=/usr/bin if test -z "$datadir" then datadir=/var/lib/mysql fi sbindir=/usr/sbin libexecdir=/usr/libexec else bindir="$basedir/bin" if test -z "$datadir" then datadir="$basedir/data" fi sbindir="$basedir/sbin" libexecdir="$basedir/libexec" fi # datadir_set is used to determine if datadir was set (and so should be # *not* set inside of the --basedir= handler.) datadir_set= # # Use LSB init script functions for printing messages, if possible # lsb_functions="/lib/lsb/init-functions" if test -f $lsb_functions ; then . $lsb_functions else log_success_msg() { echo " SUCCESS! $@" } log_failure_msg() { echo " ERROR! $@" } fi PATH=/sbin:/usr/sbin:/bin:/usr/bin:$basedir/bin export PATH mode=$1 # start or stop shift other_args="$*" # uncommon, but needed when called from an RPM upgrade action # Expected: "--skip-networking --skip-grant-tables" # They are not checked here, intentionally, as it is the resposibility # of the "spec" file author to give correct arguments only. case `echo "testing\c"`,`echo -n testing` in *c*,-n*) echo_n= echo_c= ;; *c*,*) echo_n=-n echo_c= ;; *) echo_n= echo_c='\c' ;; esac parse_server_arguments() { for arg do case "$arg" in --basedir=*) basedir=`echo "$arg" | sed -e 's/^[^=]*=//'` bindir="$basedir/bin" if test -z "$datadir_set"; then datadir="$basedir/data" fi sbindir="$basedir/sbin" libexecdir="$basedir/libexec" ;; --datadir=*) datadir=`echo "$arg" | sed -e 's/^[^=]*=//'` datadir_set=1 ;; --user=*) user=`echo "$arg" | sed -e 's/^[^=]*=//'` ;; --pid-file=*) server_pid_file=`echo "$arg" | sed -e 's/^[^=]*=//'` ;; --service-startup-timeout=*) service_startup_timeout=`echo "$arg" | sed -e 's/^[^=]*=//'` ;; --use-mysqld_safe) use_mysqld_safe=1;; --use-manager) use_mysqld_safe=0;; esac done } parse_manager_arguments() { for arg do case "$arg" in --pid-file=*) pid_file=`echo "$arg" | sed -e 's/^[^=]*=//'` ;; --user=*) user=`echo "$arg" | sed -e 's/^[^=]*=//'` ;; esac done } wait_for_pid () { verb="$1" manager_pid="$2" # process ID of the program operating on the pid-file i=0 avoid_race_condition="by checking again" while test $i -ne $service_startup_timeout ; do case "$verb" in 'created') # wait for a PID-file to pop into existence. test -s $pid_file && i='' && break ;; 'removed') # wait for this PID-file to disappear test ! -s $pid_file && i='' && break ;; *) echo "wait_for_pid () usage: wait_for_pid created|removed manager_pid" exit 1 ;; esac # if manager isn't running, then pid-file will never be updated if test -n "$manager_pid"; then if kill -0 "$manager_pid" 2>/dev/null; then : # the manager still runs else # The manager may have exited between the last pid-file check and now. if test -n "$avoid_race_condition"; then avoid_race_condition="" continue # Check again. fi # there's nothing that will affect the file. log_failure_msg "Manager of pid-file quit without updating file." return 1 # not waiting any more. fi fi echo $echo_n ".$echo_c" i=`expr $i + 1` sleep 1 done if test -z "$i" ; then log_success_msg return 0 else log_failure_msg return 1 fi } # Get arguments from the my.cnf file, # the only group, which is read from now on is [mysqld] if test -x ./bin/my_print_defaults then print_defaults="./bin/my_print_defaults" elif test -x $bindir/my_print_defaults then print_defaults="$bindir/my_print_defaults" elif test -x $bindir/mysql_print_defaults then print_defaults="$bindir/mysql_print_defaults" else # Try to find basedir in /etc/my.cnf conf=/etc/my.cnf print_defaults= if test -r $conf then subpat='^[^=]*basedir[^=]*=\(.*\)$' dirs=`sed -e "/$subpat/!d" -e 's//\1/' $conf` for d in $dirs do d=`echo $d | sed -e 's/[ ]//g'` if test -x "$d/bin/my_print_defaults" then print_defaults="$d/bin/my_print_defaults" break fi if test -x "$d/bin/mysql_print_defaults" then print_defaults="$d/bin/mysql_print_defaults" break fi done fi # Hope it's in the PATH ... but I doubt it test -z "$print_defaults" && print_defaults="my_print_defaults" fi # # Read defaults file from 'basedir'. If there is no defaults file there # check if it's in the old (depricated) place (datadir) and read it from there # extra_args="" if test -r "$basedir/my.cnf" then extra_args="-e $basedir/my.cnf" else if test -r "$datadir/my.cnf" then extra_args="-e $datadir/my.cnf" fi fi parse_server_arguments `$print_defaults $extra_args mysqld server mysql_server mysql.server` # Look for the pidfile parse_manager_arguments `$print_defaults $extra_args manager` # # Set pid file if not given # if test -z "$pid_file" then pid_file=$datadir/mysqlmanager-`/bin/hostname`.pid else case "$pid_file" in /* ) ;; * ) pid_file="$datadir/$pid_file" ;; esac fi if test -z "$server_pid_file" then server_pid_file=$datadir/`/bin/hostname`.pid else case "$server_pid_file" in /* ) ;; * ) server_pid_file="$datadir/$server_pid_file" ;; esac fi case "$mode" in 'start') # Start daemon # Safeguard (relative paths, core dumps..) cd $basedir manager=$bindir/mysqlmanager if test -x $libexecdir/mysqlmanager then manager=$libexecdir/mysqlmanager elif test -x $sbindir/mysqlmanager then manager=$sbindir/mysqlmanager fi echo $echo_n "Starting MySQL" if test -x $manager -a "$use_mysqld_safe" = "0" then if test -n "$other_args" then log_failure_msg "MySQL manager does not support options '$other_args'" exit 1 fi # Give extra arguments to mysqld with the my.cnf file. This script may # be overwritten at next upgrade. $manager --user=$user --pid-file=$pid_file >/dev/null 2>&1 & wait_for_pid created $!; return_value=$? # Make lock for RedHat / SuSE if test -w /var/lock/subsys then touch /var/lock/subsys/mysqlmanager fi exit $return_value elif test -x $bindir/mysqld_safe then # Give extra arguments to mysqld with the my.cnf file. This script # may be overwritten at next upgrade. pid_file=$server_pid_file $bindir/mysqld_safe --datadir=$datadir --pid-file=$server_pid_file $other_args >/dev/null 2>&1 & wait_for_pid created $!; return_value=$? # Make lock for RedHat / SuSE if test -w /var/lock/subsys then touch /var/lock/subsys/mysql fi exit $return_value else log_failure_msg "Couldn't find MySQL manager ($manager) or server ($bindir/mysqld_safe)" fi ;; 'stop') # Stop daemon. We use a signal here to avoid having to know the # root password. # The RedHat / SuSE lock directory to remove lock_dir=/var/lock/subsys/mysqlmanager # If the manager pid_file doesn't exist, try the server's if test ! -s "$pid_file" then pid_file=$server_pid_file lock_dir=/var/lock/subsys/mysql fi if test -s "$pid_file" then mysqlmanager_pid=`cat $pid_file` echo $echo_n "Shutting down MySQL" kill $mysqlmanager_pid # mysqlmanager should remove the pid_file when it exits, so wait for it. wait_for_pid removed "$mysqlmanager_pid"; return_value=$? # delete lock for RedHat / SuSE if test -f $lock_dir then rm -f $lock_dir fi exit $return_value else log_failure_msg "MySQL manager or server PID file could not be found!" fi ;; 'restart') # Stop the service and regardless of whether it was # running or not, start it again. if $0 stop $other_args; then $0 start $other_args else log_failure_msg "Failed to stop running server, so refusing to try to start." exit 1 fi ;; 'reload'|'force-reload') if test -s "$server_pid_file" ; then read mysqld_pid < $server_pid_file kill -HUP $mysqld_pid && log_success_msg "Reloading service MySQL" touch $server_pid_file else log_failure_msg "MySQL PID file could not be found!" exit 1 fi ;; 'status') # First, check to see if pid file exists if test -s "$server_pid_file" ; then read mysqld_pid < $server_pid_file if kill -0 $mysqld_pid 2>/dev/null ; then log_success_msg "MySQL running ($mysqld_pid)" exit 0 else log_failure_msg "MySQL is not running, but PID file exists" exit 1 fi else # Try to find appropriate mysqld process mysqld_pid=`pidof $sbindir/mysqld` if test -z $mysqld_pid ; then if test "$use_mysqld_safe" = "0" ; then lockfile=/var/lock/subsys/mysqlmanager else lockfile=/var/lock/subsys/mysql fi if test -f $lockfile ; then log_failure_msg "MySQL is not running, but lock exists" exit 2 fi log_failure_msg "MySQL is not running" exit 3 else log_failure_msg "MySQL is running but PID file could not be found" exit 4 fi fi ;; *) # usage echo "Usage: $0 {start|stop|restart|reload|force-reload|status} [ MySQL server options ]" exit 1 ;; esac exit 0 An unimportant aside: The previous users of the machine kept a messy home directory. Their home directory was /root. I've pasted a copy at http://www.pastebin.ca/2167496. My question: Why is there a /etc/init.d/mysql file on this Slackware machine? How could it have gotten there? P.S. This question is far from perfect. Please feel free to edit it.

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  • Add keyboard languages to XP, Vista, and Windows 7

    - by Matthew Guay
    Do you regularly need to type in multiple languages in Windows?  Here we’ll show you the easy way to add and change input languages to your keyboard in XP, Vista, and Windows 7. Windows Vista and 7 come preinstalled with support for viewing a wide variety of languages, so adding an input language is fairly simply.  Adding an input language is slightly more difficult in XP, and requires installing additional files if you need an Asian or Complex script language.  First we show how to add an input language in Windows Vista and 7; it’s basically the same in both versions.  Then, we show how to add a language to XP, and also how to add Complex Script support.  Please note that this is only for adding an input language, which will allow you to type in the language you select.  This does not change your user interface language. Change keyboard language in Windows 7 and Vista It is fairly simple to add or change a keyboard language in Windows 7 or Vista.  In Windows 7, enter “keyboard language” in the Start menu search box, and select “Change keyboards or other input methods”. In Windows Vista, open Control Panel and enter “input language” in the search box and select “Change keyboards or other input methods”.  This also works in Windows 7. Now, click Change Keyboards to add another keyboard language or change your default one. Our default input language is US English, and our default keyboard is the US keyboard layout.  Click Add to insert another input language while still leaving your default input language installed. Here we selected the standard Thai keyboard language (Thai Kedmanee), but you can select any language you want.  Windows offers almost any language you can imagine, so just look for the language you want, select it, and click Ok. Alternately, if you want, you can click Preview to see your layout choice before accepting it.  This is only the default characters, not ones that will be activated with Shift or other keys (many Asian languages use many more characters than English, and require the use of Shift and other keys to access them all).  Once your finished previewing, click close and then press Ok on the previous dialog. Now you will see both of your keyboard languages in the Installed services box.  You can click Add to go back and get more, or move your selected language up or down (to change its priority), or simply click Apply to add the new language. Also, you can now change the default input language from the top menu.  This is the language that your keyboard will start with when you boot your computer.  So, if you mainly use English but also use another language, usually it is best to leave English as your default input language. Once you’ve pressed Apply or Ok, you will see a new icon beside your system tray with the initials of your default input language. If you click it, you can switch between input languages.  Alternately you can switch input languages by pressing Alt+Shift on your keyboard. Some complex languages, such as Chinese, may have extra buttons to change input modes to accommodate their large alphabet. If you would like to change the keyboard shortcut for changing languages, go back to the Input Languages dialog, and select the “Advanced Key Settings” tab.  Here you can change settings for Caps Lock and change or add key sequences to change between languages. Also, the On-Screen keyboard will display the correct keyboard language (here the keyboard is displaying Thai), which can be a helpful reference if your physical keyboard doesn’t have your preferred input language printed on it.  To open this, simply enter “On-Screen keyboard” in the start menu search, or click All Programs>Accessories>On-Screen keyboard. Change keyboard language in Windows XP The process for changing the keyboard language in Windows XP is slightly different.  Open Control Panel, and select “Date, Time, Language, and Regional Options”.   Select “Add other languages”. Now, click Details to add another language.  XP does not include support for Asian and complex languages by default, so if you need to add one of those languages we have details for that below. Click Add to add an input language. Select your desired language from the list, and choose your desired keyboard layout if your language offers multiple layouts.  Here we selected Canadian French with the default layout. Now you will see both of your keyboard languages in the Installed services box.  You can click Add to go back and add more, or move your selected language up or down (to change its priority), or simply click Apply to add the new language. Once you’ve pressed Apply or Ok, you will see a new icon beside your system tray with the initials of your default input language. If you click it, you can switch between input languages.  Alternately you can switch input languages by pressing Alt+Shift on your keyboard. If you would like to change the keyboard shortcut for changing languages, go back to the Input Languages dialog, and click the “Key Settings” button on the bottom of the dialog.  Here you can change settings for Caps Lock and change or add key sequences to change between languages. Add support to XP for Asian and Complex script languages Windows XP does not include support for Asian and Complex script languages by default, but you can easily add them to your computer.  This is useful if you wish to type in one of these languages, or simply want to read text written in these languages, since XP will not display these languages correctly if they are not installed.  If you wish to install Chinese, Japanese, and/or Korean, check the “Install files for East Asian languages” box.  Or, if you need to install a complex script language (including Arabic, Armenian, Georgian, Hebrew, the Indic languages, Thai, and Vietnamese), check the “Install files for complex script and right-to-left languages” box.   Choosing either of these options will open a prompt reminding you that this option will take up more disk space.  Support for complex languages will require around 10Mb of hard drive space, but East Asian language support may require 230 Mb or more free disk space.  Click Ok, and click apply to install your language files. You may have to insert your XP CD into your CD drive to install these files.  Insert the disk, and then click Ok. Windows will automatically copy the files, including fonts for these languages… …and then will ask you to reboot your computer to finalize the settings.  Click Yes, and then reopen the “Add other languages” dialog when your computer is rebooted, and add a language as before.     Now you can add Complex and/or Asian languages to XP, just as above.  Here is the XP taskbar language selector with Thai installed. Conclusion Unfortunately we haven’t found a way to add Asian and complex languages in XP without having an XP disc. If you know of a way, let us know in the comments. (No downloading the XP disc from torrent site answers please) Adding an input language is very important for bilingual individuals, and can also be useful if you simply need to occasionally view Asian or Complex languages in XP.  And by following the correct instructions for your version of Windows, it should be very easy to add, change, and remove input languages. Similar Articles Productive Geek Tips Show Keyboard Shortcut Access Keys in Windows VistaKeyboard Ninja: 21 Keyboard Shortcut ArticlesAnother Desktop Cube for Windows XP/VistaThe "Up" Keyboard Shortcut for Windows 7 or Vista ExplorerWhat is ctfmon.exe And Why Is It Running? 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 Revo Uninstaller Pro Registry Mechanic 9 for Windows PC Tools Internet Security Suite 2010 PCmover Professional Make your Joomla & Drupal Sites Mobile with OSMOBI Integrate Twitter and Delicious and Make Life Easier Design Your Web Pages Using the Golden Ratio Worldwide Growth of the Internet How to Find Your Mac Address Use My TextTools to Edit and Organize Text

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  • which xml validator will work perfectly for multithreading project

    - by Sunil Kumar Sahoo
    Hi All, I have used jdom for xml validation against schema. The main problem there is that it gives an error FWK005 parse may not be called while parsing The main reason was that multiple of threads working for xerces validation at the same time. SO I got the solution that i have to lock that validation. which is not good So I want to know which xml validator works perfectly for multithreading project public static HashMap validate(String xmlString, Validator validator) { HashMap<String, String> map = new HashMap<String, String>(); long t1 = System.currentTimeMillis(); DocumentBuilder builder = null; try { //obtain lock to proceed // lock.lock(); try { builder = DocumentBuilderFactory.newInstance().newDocumentBuilder(); // Source source = new DOMSource(builder.parse(new ByteArrayInputStream(xmlString.getBytes()))); validator.validate(new StreamSource(new StringReader(xmlString))); map.put("ISVALID", "TRUE"); logger.info("We have successfuly validated the schema"); } catch (Exception ioe) { ioe.printStackTrace(); logger.error("NOT2 VALID STRING IS :" + xmlString); map.put("MSG", ioe.getMessage()); // logger.error("IOException while validating the input XML", ioe); } logger.info(map); long t2 = System.currentTimeMillis(); logger.info("XML VALIDATION TOOK:::" + (t2 - t1)); } catch (Exception e) { logger.error(e); } finally { //release lock // lock.unlock(); builder = null; } return map; } Thanks Sunil Kumar Sahoo

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  • ADO.NET DataTable/DataRow Thread Safety

    - by Allen E. Scharfenberg
    Introduction A user reported to me this morning that he was having an issue with inconsistent results (namely, column values sometimes coming out null when they should not be) of some parallel execution code that we provide as part of an internal framework. This code has worked fine in the past and has not been tampered with lately, but it got me to thinking about the following snippet: Code Sample lock (ResultTable) { newRow = ResultTable.NewRow(); } newRow["Key"] = currentKey; foreach (KeyValuePair<string, object> output in outputs) { object resultValue = output.Value; newRow[output.Name] = resultValue != null ? resultValue : DBNull.Value; } lock (ResultTable) { ResultTable.Rows.Add(newRow); } (No guarantees that that compiles, hand-edited to mask proprietery information.) Explanation We have this cascading type of locking code other places in our system, and it works fine, but this is the first instance of cascading locking code that I have come across that interacts with ADO .NET. As we all know, members of framework objects are usually not thread safe (which is the case in this situation), but the cascading locking should ensure that we are not reading and writing to ResultTable.Rows concurrently. We are safe, right? Hypothesis Well, the cascading lock code does not ensure that we are not reading from or writing to ResultTable.Rows at the same time that we are assigning values to columns in the new row. What if ADO .NET uses some kind of buffer for assigning column values that is not thread safe--even when different object types are involved (DataTable vs. DataRow)? Has anyone run into anything like this before? I thought I would ask here at StackOverflow before beating my head against this for hours on end :) Conclusion Well, the consensus appears to be that changing the cascading lock to a full lock has resolved the issue. That is not the result that I expected, but the full lock version has not produced the issue after many, many, many tests. The lesson: be wary of cascading locks used on APIs that you do not control. Who knows what may be going on under the covers!

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  • In C/C++ mode in Emacs, change face of code in #if 0...#endif block to comment face

    - by pogopop77
    I'm trying to add functionality found in some other code editors to my Emacs configuration, whereby C/C++ code within #if 0...#endif blocks is automatically set to the comment face/font. Based on my testing, cpp-highlight-mode does something like what I want, but requires user action. It seems like tying into the font-lock functionality is the correct option to make the behavior automatic. I have successfully followed examples in the GNU documentation to change the face of single-line regular expressions. For example: (add-hook 'c-mode-common-hook (lambda () (font-lock-add-keywords nil '(("\\<\\(FIXME\\|TODO\\|HACK\\|fixme\\|todo\\|hack\\)" 1 font-lock-warning-face t))))) works fine to highlight debug related keywords anywhere in a file. However, I am having problems matching #if 0...#endif as a multiline regular expression. I found some useful information in this post (How to compose region like ""), that suggested that Emacs must be told specifically to allow for multiline matches. But this code: (add-hook 'c-mode-common-hook (lambda () '(progn (setq font-lock-multiline t) (font-lock-add-keywords nil '(("#if 0\\(.\\|\n\\)*?#endif" 1 font-lock-comment-face t)))))) still does not work for me. Perhaps my regular expression is wrong (though it appears to work using M-x re-builder), I've messed up my syntax, or I'm following the wrong approach entirely. I'm using Aquamacs 2.1 (which is based on GNU Emacs 23.2.50.1) on OS X 10.6.5, if that makes a difference. Any assistance would be appreciated!

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  • implementing the generic interface

    - by user845405
    Could any one help me on implementing the generic interface for this class. I want to be able to use the below Cache class methods through an interface. Thank you for the help!. public class CacheStore { private Dictionary<string, object> _cache; private object _sync; public CacheStore() { _cache = new Dictionary<string, object>(); _sync = new object(); } public bool Exists<T>(string key) where T : class { Type type = typeof(T); lock (_sync) { return _cache.ContainsKey(type.Name + key); } } public bool Exists<T>() where T : class { Type type = typeof(T); lock (_sync) { return _cache.ContainsKey(type.Name); } } public T Get<T>(string key) where T : class { Type type = typeof(T); lock (_sync) { if (_cache.ContainsKey(key + type.Name) == false) throw new ApplicationException(String.Format("An object with key '{0}' does not exists", key)); lock (_sync) { return (T)_cache[key + type.Name]; } } } public void Add<T>(string key, T value) { Type type = typeof(T); if (value.GetType() != type) throw new ApplicationException(String.Format("The type of value passed to cache {0} does not match the cache type {1} for key {2}", value.GetType().FullName, type.FullName, key)); lock (_sync) { if (_cache.ContainsKey(key + type.Name)) throw new ApplicationException(String.Format("An object with key '{0}' already exists", key)); lock (_sync) { _cache.Add(key + type.Name, value); } } } } Could any one help me on implementing the generic interface for this class. I want to be able to use the below Cache class methods through an interface.

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  • How to synchronize access to many objects

    - by vividos
    I have a thread pool with some threads (e.g. as many as number of cores) that work on many objects, say thousands of objects. Normally I would give each object a mutex to protect access to its internals, lock it when I'm doing work, then release it. When two threads would try to access the same object, one of the threads has to wait. Now I want to save some resources and be scalable, as there may be thousands of objects, and still only a hand full of threads. I'm thinking about a class design where the thread has some sort of mutex or lock object, and assigns the lock to the object when the object should be accessed. This would save resources, as I only have as much lock objects as I have threads. Now comes the programming part, where I want to transfer this design into code, but don't know quite where to start. I'm programming in C++ and want to use Boost classes where possible, but self written classes that handle these special requirements are ok. How would I implement this? My first idea was to have a boost::mutex object per thread, and each object has a boost::shared_ptr that initially is unset (or NULL). Now when I want to access the object, I lock it by creating a scoped_lock object and assign it to the shared_ptr. When the shared_ptr is already set, I wait on the present lock. This idea sounds like a heap full of race conditions, so I sort of abandoned it. Is there another way to accomplish this design? A completely different way?

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  • Why does java.util.concurrent.ArrayBlockingQueue use 'while' loops instead of 'if' around calls to

    - by theFunkyEngineer
    I have been playing with my own version of this, using 'if', and all seems to be working fine. Of course this will break down horribly if signalAll() is used instead of signal(), but if only one thread at a time is notified, how can this go wrong? Their code here - check out the put() and take() methods; a simpler and more-to-the-point implementation can be seen at the top of the JavaDoc for Condition. Relevant portion of my implementation below. public Object get() { lock.lock(); try { if( items.size() < 1 ) hasItems.await(); Object poppedValue = items.getLast(); items.removeLast(); hasSpace.signal(); return poppedValue; } catch (InterruptedException e) { e.printStackTrace(); return null; } finally { lock.unlock(); } } public void put(Object item) { lock.lock(); try { if( items.size() >= capacity ) hasSpace.await(); items.addFirst(item); hasItems.signal(); return; } catch (InterruptedException e) { e.printStackTrace(); } finally { lock.unlock(); } } P.S. I know that generally, particularly in lib classes like this, one should let the exceptions percolate up.

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  • Inverted schedctl usage in the JVM

    - by Dave
    The schedctl facility in Solaris allows a thread to request that the kernel defer involuntary preemption for a brief period. The mechanism is strictly advisory - the kernel can opt to ignore the request. Schedctl is typically used to bracket lock critical sections. That, in turn, can avoid convoying -- threads piling up on a critical section behind a preempted lock-holder -- and other lock-related performance pathologies. If you're interested see the man pages for schedctl_start() and schedctl_stop() and the schedctl.h include file. The implementation is very efficient. schedctl_start(), which asks that preemption be deferred, simply stores into a thread-specific structure -- the schedctl block -- that the kernel maps into user-space. Similarly, schedctl_stop() clears the flag set by schedctl_stop() and then checks a "preemption pending" flag in the block. Normally, this will be false, but if set schedctl_stop() will yield to politely grant the CPU to other threads. Note that you can't abuse this facility for long-term preemption avoidance as the deferral is brief. If your thread exceeds the grace period the kernel will preempt it and transiently degrade its effective scheduling priority. Further reading : US05937187 and various papers by Andy Tucker. We'll now switch topics to the implementation of the "synchronized" locking construct in the HotSpot JVM. If a lock is contended then on multiprocessor systems we'll spin briefly to try to avoid context switching. Context switching is wasted work and inflicts various cache and TLB penalties on the threads involved. If context switching were "free" then we'd never spin to avoid switching, but that's not the case. We use an adaptive spin-then-park strategy. One potentially undesirable outcome is that we can be preempted while spinning. When our spinning thread is finally rescheduled the lock may or may not be available. If not, we'll spin and then potentially park (block) again, thus suffering a 2nd context switch. Recall that the reason we spin is to avoid context switching. To avoid this scenario I've found it useful to enable schedctl to request deferral while spinning. But while spinning I've arranged for the code to periodically check or poll the "preemption pending" flag. If that's found set we simply abandon our spinning attempt and park immediately. This avoids the double context-switch scenario above. One annoyance is that the schedctl blocks for the threads in a given process are tightly packed on special pages mapped from kernel space into user-land. As such, writes to the schedctl blocks can cause false sharing on other adjacent blocks. Hopefully the kernel folks will make changes to avoid this by padding and aligning the blocks to ensure that one cache line underlies at most one schedctl block at any one time.

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  • Unintentional run-in with C# thread concurrency

    - by geekrutherford
    For the first time today we began conducting load testing on a ASP.NET application already in production. Obviously you would normally want to load test prior to releasing to a production environment, but that isn't the point here.   We ran a test which simulated 5 users hitting the application doing the same actions simultaneously. The first few pages visited seemed fine and then things just hung for a while before the test failed. While the test was running I was viewing the performance counters on the server noting that the CPU was consistently pegged at 100% until the testing tool gave up.   Fortunately the application logs all exceptions including those unhandled to the database (thanks to log4net). I checked the log and low and behold the error was:   System.ArgumentException: An item with the same key has already been added. (The rest of the stack trace intentionally omitted)   Since the code was running with debug on the line number where the exception occured was also provided. I began inspecting the code and almost immediately it hit me, the section of code responsible for the exception is trying to initialize a static class. My next question was how is this code being hit multiple times when I have a rudimentary check already in place to prevent this kind of thing (i.e. a check on a public variable of the static class before entering the initializing routine). The answer...the check fails because the value is not set before other threads have already made it through.   Not being one who consistently works with threading I wasn't quite sure how to handle this problem. Fortunately a co-worker recalled having to lock a section of code in the past but couldn't recall exactly how. After a quick search on Google the solution is as follows:   Object objLock = new Object(); lock(objLock) { //logic requiring lock }   The lock statement takes an object and tells the .NET runtime that the current thread has exclusive access while the code within brackets is executing. Once the code completes, the lock is released for another thread to utilize.   In my case, I only need to execute the inner code once to initialize my static class. So within the brackets I have a check on a public variable to prevent it from being initialized again.

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  • Exclusive use of a Jini server during long-running call

    - by Matthew Flint
    I'm trying to use Jini, in a "Masters/Workers" arrangement, but the Worker jobs may be long running. In addition, each worker needs to have exclusive access to a singleton resource on that machine. As it stands, if a Worker receives another request while a previous request is running, then the new request is accepted and executed in a second thread. Are there any best-practices to ensure that a Worker accepts no further jobs until the current job is complete? Things I've considered: synchronize the job on the server, with a lock on the singleton resource. This would work, but is far from ideal. A call from a Master would block until the current Worker thread completes, even if other Workers become free in the meantime unregister the Worker from the registry while the job is running, then re-register when it completes. Might work OK, but something doesn't smell right with this idea... Of course, I'm quite happy to be told that there are more appropriate technologies than Jini... but I wouldn't want anything too heavyweight, like rolling out EJB containers all over the place.

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