Is there anyway in Linux that can achieve atomic increment/decrement for an integer variable without being interrupted? It means that the thread should not chance for other thread to run until theincrement/decrement is completed.
View 11 RepliesI have an big doubt in increment and decrement in c programmingi am trying to compile the below code in gcc
Code:
#include<stdio.h>
main()
[code]....
I'm running cygwin 1.7.7 on a win2k3R2 Standard edition server. I have a RHEL 4.7 linux host I'm scp'ing files from to the windows system using a simple cygwin scp command from what appears to be OpenSSH_5.5p1 on the cygwin host. When I run the simple scp command on the cygwin host, the counters initially display and increment/decrement, albeit what is at a much slower rate than is actually taking place. After the percent complete reaches a little less than 10%, all the counters from the cygwin console window cease to increment/decrement.
However, when I cd to the directory on the cygwin host where the file is being scp'ed to, the file is continuing to be transferred and a much higher rate than the counters seem to show. Finally, when the file transfer is complete by directly seeing the byte count as equal between the hosts, the scp counters will suddenly jump to 100% complete. This is not the case with my linux to linux scp's. The counters increment/decrement as expected and transfers are about what I'd expect over the same network infrastructure. This appears to be a cygwin ssh/scp implementation issue. I've posited this question to cygwin with no response as yet. The only reference I've been able to find on the 'net refers to buffering causing file transfers to appear to complete later than the transfer really does..........
have two shared variables a,b which are related to each other.When multiple applications share these shared variables, access to them needs to be an atomic operation, otherwise the relation may break. So to ensure mutual exclusion, I'll put their modification under a critical section protected by lock.
Code:
critical_code
{
P(mutex)
a := something
b := something
V(mutex)
}
Lets say my hardware/OS/compiler supports atomic variables. Then I modified my above code as follows.
Code:
code
{
atomic a := something
atomic b := something
}
Can this code ensure mutual exclusion, when accessed by multiple applications?
Can one of you point me towards a comprehensive print function tutorial in perl? I was under the impression that everything within quotes will get interpolated - but I am running into exceptions where it is not desirable to run some varaibles under quotes.
ordinal.pl
1 #!/usr/bin/perl
2 $idx = 1;
3 foreach $letter (a..z) {
4 print "Letter #",$idx++," is: $letter
";
5 #print "Letter # $idx++ is: $letter
[Code]...
How do I get this loop to stop on each increment? This script does work but I would like it to stop at each increment, remember what the value of $n is, then continue until it gets to 7. I have worked so hard on this. My brain is hurting now.
[Code]...
I work in a simulations environment. I'm trying to write a bash script that will read fields from a .csv file into an array, the first field being an identifiyng number and the second field being a corresponding url. There are about 1600 of these number/url combinations in the .csv file that i'm reading from. Once that is done i want it to parse a text file and match the number, when it has a match i want it to enter the corresponding url into a particular line in the text file. The script I have written (with the help of the people on this forum a while back) does this well, but now I have a lot more data to parse. I think the script itself is explanatory enough to see what i'm doing. What i would like to do is cut it down to one while loop nested inside another loop so that I don't have 1600 or so elif statements. I can't figure out how to increment the output of the array. for instance, the first cycle would find the number that matches ${record1[2]} and input the url stored in ${record1[3]}. the next cycle would match ${record1[4]} and input the url in ${record1[5]}, and so on, does that make sense? The code is below and a sample .csv and text file are attached.
[Code]...
How to achieve interrupts
any sources available apart from kernel code which show the usage of code...
How can I achieve file consistency while using mmap? I have a block of code that needs synchronized access across processes (not threads). Using threads, one can regulate access to the mmaped portion of the file by locking it using a mutex. How can I achieve the same using different processes, some of which run in different programs?
View 2 Replies View Relatedhow do I achieve the result but here is the story. I have a script which prompts for the IP Address and read that value and validate if reachable. If not then it should keep on prompting until the IP is reachable. I tried using until loop as well as while loop but dang..Here are the codes
#!/bin/bash
IP_Feed () {
echo -n "Give me IP : "
[code]....
When I'm recompiling apache and php, it doesn't go through and I get this error:
Code:
checking for atomic.h... no
/usr/include/mysql/my_global.h:364:24: error: asm/atomic.h: No such file or directory
[code]....
I'm only somewhat new to linux but I still don't have a real grasp of it's deep innards and I had a fairly outlandish idea that I'm wondering whether is possible/plausible or not.I want to run a game server on CentOS that has a very high dependency on fast writes-to-disk. Disk writes are pretty much the single bottleneck in this server.First I looked at allowing a high queue of writes to pile up before it flushes them to the disk, but I read that this causes fsync, which is still used commonly, to take a very long time.
I've been thinking about the possibility of running the server on a RAM disk, but I still want changes to be saved to non-volatile storage. Not all at once, but have it actively write the changes to disk. The hope is that this would smooth out the peaks and valleys of write activity and improve overall performance, but I have not seen this idea discussed anywhere.
So my question is, is there any plausible way to continuously copy writes to a RAM disk to a physical drive without slowing down the speed of the writes to the RAM drive below the speed of said RAM? Or is there a better way to obtain this sort of performance, short of investing in expensive equipment?
I need to insure the "writer" to named shared memory (small size, 160 bytes) completes his task such that the many "readers" always get the latest data. The machine is a multi-processor (8 CPU, 24 Gig RAM), non-real time system. The system has multiple processes that are also multi-threaded. Thankfully, there is only 1 "writer" and many "readers". There is no semaphore or mutex locking. "Readers" must not block each other and especially not block the "writer".
By design, it is expected from time to time a "reader" will be in the middle of reading when the "writer" begins to update the data. I want to protect against the case of the "writer" being interrupted and a "reader" completes it's read before the "writer" wakes up and completes it's changes. In this case the "reader" will get corrupt data, some new and some old.
So I have a field in my table called "id" and this is the primary key for the table which is also configured to 'auto_increment' as show below:
Code:
mysql> describe users;
+------------+-------------+------+-----+---------+----------------+
[code]....
According to [URL], gcc 4.3 supports atomic built-in function "GCC can now use load-linked, store-conditional and sync instructions to implement atomic built-in functions such as __sync_fetch_and_add" However, I am still using gcc 3.4 on my Redhat EL4. How do I get this built-in function installed?
View 2 Replies View RelatedI have this hdd and another with XP in it but when ever I chnage to UBuntu, the clock goes out of whack and, makes me manually change it whereas in my XP I have an atomic clock installed that I just click on 'Ping' and she's right. I've looked at heaps of downloads for similar on here but, I haven't found a free one other than a trial type that I'm not interested in, that works so, why is Linux so difficult in this regard? I will accept all the help I can get on here because I like the thought of being able to get away from Microsoft.
View 2 Replies View RelatedI tried searching for this, but everything, for pages and pages, shows me the `if -e filename`. That's not what I'm looking for, at least I don't think I am. I am working on a script that will search a directory for certain file names and increment a variable by one for each result returned. Each time I search this file name, the file found will also be deleted. I would like this script to be run about every 6 hours or so. We'll call this script A.
I also have a script that runs daily that I would like to tack the count to the end of the text file that it outputs. We'll call this script B. I'm confident that I would want to store the count from script A to a text file to be called in by script B, but don't know how to do so. Here's what I have so far:
Code:
#!/bin/bash
SD=0#Resetting variable count for testing purposes, removed this before release #Below, Smith is used for testing purposes as this is the newest backup with instances found
find /cust_backups/Smith -name *Modified Script* && SD=$[SD+1] ;
find /cust_backups/Smith -name *Bitdefender Online Scanner* && SD=$[SD+1] ;
find /cust_backups/Smith -name *ccleaner.exe* && SD=$[SD+1] ;
find /cust_backups/Smith -name *HJT.exe* && SD=$[SD+1] ;
[Code]...
Now, for those of you that know what you're doing, you're already shaking your head because you know that, no matter what, at the end of the script $SD will end up being 14. The problem is I don't know how to tell bash that if there is a result returned, increment by one. If there is no result returned, move to the next command. Beyond that, I'll need to know how to call the text of a file in to a variable so I can plug it in to the text output of script B.
What is the procedure to increment the number under the cursor ? 12 Which key i have to press to make this 12 to become 13. I know the method of keeping the number in register and incrementing, But am looking for a single key to increment the number under cursor.
View 2 Replies View RelatedIntroduction : We have a C++ application in RHEL 5.4 platform. We are using TCP/IP socket programming as well to send and receive some sort of messages. We are using socket write and read command for this purpose and we are getting some run-time write issues in between. By doing various debugging and strace operations, we came to the conclusion that issue happens in some write attempts as follows.
Detailed Description : In the simplest case, consider I have a server and a client. Server writes some messages using write command and client is supposed to read the same data.Major code snippets in Server side is as follows [It is not feasible to extract the actual files and application codes as a whole, below are just the major commands used in server side]:
sockfd = socket(AF_INET, SOCK_STREAM, 0);
int reuse=1;
setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR,& reuse, sizeof(reuse));
[code]....
I wasn't sure if this is the right place to ask or comment on this, but since it's about Apache web server I thought it should work. I finally figured out how to set up and bring up the site using virtual hosts in Apache, though at the moment it's just for my localhost install.
I set them up so I can have a place to play with possible new themes and/or test out the Drupal 7 alpha / beta releases without messing up my current configuration. I decided to look at the error logs for the currently configured site and it had a lot of messages similar to the following:
[Sat Mar 06 09:45:39 2010] [error] [client 127.0.0.1] ModSecurity: Unable to retrieve collection (name "ip", key "127.0.0.1"). Use SecDataDir to define data directory first. [hostname "site.local"] [uri "/"] [unique_id "ZnUHgsCoAAEAABdzR2QAAAAB"]
I got some sourcecode written with c++. I found it did not supported by the newer version of gcc. So I wanted to install an older version. But it always comes up with the question like "./read-rtl.c:653: error: lvalue required as increment operand", what should I do now?
View 6 Replies View RelatedIs there a way I can change the volume increase/decrees increments
View 5 Replies View RelatedWhat GNOME does with pendrives does surprise me. It not only umounts the partitions, but also shuts the device down and turns off the power light. How do I achieve the same effect with CLI? I've tried eject but it does not cut power.
View 10 Replies View RelatedI'm working on some code from my computer at home and would like to do CVS updates to a remote server. When I'm at work I don't need to type in a password, but at home each time I need to type in my password each time I do a CVS update. I've followed the instructions here on how to set up a passwordless public/private ssh key pair: [URL].. However, after that I still need to type in my ssh password each time I do CVS update (or anything CVS related) from my local computer.
View 1 Replies View RelatedI have a video I want to convert to another video format that's similar to another video. The video's properties and codecs as follows:
Code:
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'Vid.mp4':
Duration: 00:02:35.80, start: 0.000000, bitrate: 1731 kb/s
Audio: adpcm_ima_wav, 22050 Hz, stereo, s16
Video: mjpeg, yuvj420p, 128x128 [PAR 1:1 DAR 1:1], 30 tbr, 30 tbn, 30 tbc
I have install fedora12 in a virtual machine (oracle VBox) in a windows vista host (I know aaarg) and i can't have a fullscreen mode for the fedora I don't know, if it is cause additional features are needed for fedora or is something from the VBox and some additional features of it are needed any special arrangment is needed into the operetional parameters of the VBox.
View 2 Replies View RelatedI have configured /etc/syslog.conf for writing user level log messages, and it is working fine.
The line which i entered is: user.* /home/shekhar/obj/myjob.log
But the log file keeps increasing. I would like to rotate the log file when it reaches 100Kb.
How do i do that in red hat linux ?
How to achieve this effect of mouse?which function or api?see the imag:http://linux.chinaunix.net/bbs/attac...Z2uSUDstxs.png
View 6 Replies View RelatedI'm installing 11.4 as a guest under Citrix's XenServer. The only access to a guest's graphical desktop is via VNC.The problem is that I can't achieve runlevel 5 as X can't find any devices. With 11.3 I was able to run Sax2 and add a dummy screen device to Xorg.conf that it created.When Sax2 was removed from 11.4, what was the fall-back for configuring X?
View 5 Replies View Relatedcopy old backups from 600+ CD/DVD media to a hard disk. Machine: A desktop with 4 DVD drivers, mainboard has 4 SATA conectors and only one PATA conector. My questions are:
1. What tuning can I do to the kernel on a Ubuntu Lucid Desktop to achieve maximum IO to dd/cp/rsync/whatever those medias to hd?
2. What's the best scenario regarding HD/DVD drive connections to mainboard regarding IO/throughput?
The intention is to insert 4 medias at a time and copy them all in parallel to a local hard disk.