Programming :: Create A Shared Memory And Some Shared Objects?
Jun 11, 2010
I want to create a "Shared Memory" in linux, then create multiple "Shared Objects" that can access to a Table for example; And one of them can write something into the Table and the other can access and read it, so that these operations can be handled by programmer! I'm using Ubuntu 9.04 and I've set it's runlevel at 3 (I have commandline environment now!) I've searched the Internet so much, but couldn't find a good sample code for this! I have no experience about it and need your help to introduce me a sample code about it and advise me how to compile and use it with "GCC"?!
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Oct 28, 2010
I have a question about shared objects and when mapping and linking is established in the following code...Well more of a verification.
getsetx.c - shared object source code Code: unsigned long x = 0;
unsigned long getx(void)
{
return x;
}
[Code].....
Now its my understanding when I execute ./testit, getsetx.so will get mapped into its address space at start up and testit will link any functions as they are needed..
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Apr 19, 2010
I have 2 applications that send and receive messages through shared memory IPC. When I run the app ..it works but the number of messages per sec keeps changing drastically sometimes it is 400-500 per sec..then 800 then 1200 then 2000. is this normal with SHM IPC or could it be a code related issue.
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Jun 1, 2009
Any good tutorial on sharing dynamically allocated objects across shared libraries in the same process and between shared libaries and main(). In particular, I need to know what creation and destruction sequences are valid when libraries are being loaded and unloaded. For example, is it valid to allocate an object from inside a shared library procedure, and then delete that pointer from a different module, especially in the case where the allocating module has already been unloaded.
I imagine there might be all kinds of problems with this. Although my preliminary tests seem to work most of the time, I get crashes from time to time, but I'm not sure if they're caused by memory management or by threading issues. I've been restructuring my code to use a global context object to manage object creation and destruction from main(), but I'd like to find a clear exposition of the specific issues I'm dealing with before I go too much further.
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Jan 8, 2011
I'm writing a producer-consumer program, where the producer and the consumer are different processes and they communicate using queued signals, and when I run it it comes out always 'segmentation fault'.
Here is my code:
(note: I tried using both 'shm_open()' and 'mmap()', and 'shmget()' and shmat()')
Code:
#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
[code]....
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Mar 17, 2010
So I'll try to be brief and to the point here: I've got a couple of C / C++ apps that communicate with one another via shared memory. These worked completely fine until.. well, about twenty minutes ago when I finished making some network card changes and suddenly, I've got a weird problem going on. At one point, Parent app waits for Child app to set a boolean indicating it's finished initialization. This worked fine the last time I ran this app up (a few days ago). But right now, the shared flag never seems to get triggered (I've added a printf("Waiting..."); in Parent app until the flag is set). All the code leading up to it being set in Child app seem to be running smoothly, so I tried spitting out the addresses of the shared memory locations. The addresses mapped by Parent app and Child app are different; this seemed odd, so I went back and wrote a simple miniature app that just opened a shared structure on my own box, and I get the same thing - different addresses - but the miniature apps work just fine.
Is it normal for a shared memory space to be mapped to two different addresses across two processes?
If so, does anyone have any idea what might be the issue at hand with my Parent / Child app scenario? The Child creates the shared memory, the Parent has a wait before it opens it, and if it doesn't exist should fail (opening with PROT_READ | PROT_WRITE)... it doesn't fail so it's evidently there.
All of this worked until literally just a few hours ago and I made some changes to my network cards, and I can't even imagine how that could have changed whether or not shared memory mapping worked...
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Jun 30, 2010
I want to know that is there any way to peep inside the shared object and see its code ?
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Feb 5, 2011
I have what should be a relatively simple program (fadec.c) that maps a struct from an included header file (fadec.h) to a shared memory region, but Im struggling accessing members in the struct from the pointer returned by shmat. Ultimately, I want to access members in the shared memory structure with a globally declared version of the struct, shm__. Not only do I not know how to accomplish that, but I cant even seem to access members of the shared struct directly from the pointer itself (compiler complains about dereferencing pointer to incomplete type). Im at a loss and could use another set of eyes if you guys dont mind taking a gander:
Compile Errors:
tony-pc:/cygdrive/p/test> cc -o fadec fadec.c
fadec.c: In function 'main':
fadec.c:30: error: dereferencing pointer to incomplete type
fadec.c:31: error: dereferencing pointer to incomplete type
[Code]...
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Mar 4, 2011
I have a program that creates and uses a shared memory segment. I am trying to find out how to detach and delete this shared memory segment when I hit crtl-C, and I still need the process to terminate.shmdt() and shmctl() have variables that are local to the main passed to them(shared and shmid)
Code:
//Prototype
void leave(int sig);
//part of code trying to use signal handling
if(signal(SIGINT, leave))
[Code]...
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Feb 21, 2011
if i attach a shared memory to my process whch part of the address space it will add(like stack, heap, data, code...).
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Mar 2, 2010
I have an application consisting of different processes and all these processes are linked to shared libraries. I start the application (spawn all the different processes) as say user1. Now with the application up, if I run a process p1, the process gets activated and works. However, if I start the same process p1 as a different user, say user2, which is completely different from user1 the process complains of
"error while loading shared libraries:...."
I set LD_RUN_PATH both in compile and runtime environment. LD_LIBRARY_PATH is set correctly in both places.
All the above works if I set the absolute path of the required shared libraries in /etc/ld.so.conf file and rebuild the /etc/ld.so.cache
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Aug 16, 2010
Alright, just loaded a fresh copy of OpenSuSE 11.3 x64, went to update manager and let it update, came back and computer was shut down. After booting it back up, I cannot update any software, nor run any commands.
Here is my output:
Code: error while loading shared libraries: libdl.so.2: cannot open shared object file: No such file or directory I've tried searching for this error, some people came back saying to run this:
Code:
But all that happens is this:
Code:
Nor ls work either so I'm stuck and thinking about a reinstall.
I don't understand how this system could be so messed up after a failed update.. Used to trust SuSE, not sure anymore after this incident..
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Nov 9, 2010
Installed Skype but it wont launch. Running the latest Opensuse Gnome. Ive uninstalled it and reinstalled several times but always with the same error. When I try to run it from terminal I get this:
ig@linux-ljqk:~> skype
skype: error while loading shared libraries: libpng12.so.0: cannot open shared object file: No such file or directory
Ive just now uninstalled skype and tried reinstalling it again via yast, but now I get the following error [PK_TMP_DIR|dir:///var/tmp/TmpDir.xftzR0] Repository already exists.
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May 5, 2010
just installed Ubuntu 10.04 and installed the flightgear package and the fgfs-base package. I ran fgfs from a terminal and got this error:
Code:
$ fgfs
fgfs: error while loading shared libraries: libOpenThreads.so.12: cannot open shared object file: No such file or directory
$
So then I did:
Code:
sudo apt-get install libopenthreads12
and it gave me these errors:
[Code]...
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Aug 3, 2010
I'm trying to run Kega Fusion on my laptop, which can now FINALLY run Linux (ATI drivers finally work on it), and I can't get the emulator to work..
Code:
brandon@brandon-laptop:~/Desktop/Fusion$ ./Fusion
./Fusion: error while loading shared libraries: libGLU.so.1: cannot open shared object file: No such file or directory
brandon@brandon-laptop:~/Desktop/Fusion$ uname -a
Linux brandon-laptop 2.6.32-24-generic #38-Ubuntu SMP Mon Jul 5 09:20:59 UTC 2010 x86_64 GNU/Linux
brandon@brandon-laptop:~/Desktop/Fusion$
Help? I have the ATI proprietary drivers installed. I tried without them and it still wouldn't work. (And OpenGL is seemingly working as Compiz Fusion is running. I also tried with Compiz disabled but the same error pops up).
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Aug 21, 2010
I'm running lucid 32-bit. I get this error when I try to run the installer for Unreal Tournament GOTY:
Code:
Verifying archive integrity... All good. Uncompressing Unreal Tournament 436-multilanguage.goty Installer. /home/computer/.setup1548: error while loading shared libraries: libgtk-1.2.so.0: cannot open shared object file: No such file or directory computer@computer-desktop:~/UnrealInstall$ I tried installing libgtk1.2 (as told by some people in other threads), but couldn't do that:
Code:
E: Couldn't find package libgtk1.2
However, I checked that I do have libgtk2.0
So what should I do?
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Jan 26, 2011
After finally getting my wireless/graphics drivers working yesterday (thanks to this forum ) I startx to realize that not a single KDE/Qt application will launch, along with Firefox, or Chrome/Chromium. (I did a full install from the DVD, not deselecting anything, and when I upgraded to -current, I also did the same.)
Ark said:
Quote:
ark: error while loading shared libraries: liblzma.so.0: cannot open shared object file: No such file or directory
but I managed to fix that one by commenting out 'aaa_elflibs' in /etc/slackpkg/blacklist (on a recommendation from #slackware), and running slackpkg upgrade-all again, but that's the only one (afaik) that was fixed. Ark still doesn't work, but it doesn't show that error anymore. When I run it, a box pops up that says "Unable to find Ark's KPart component, please check your installation."
Kate still says:
Quote:
kate: error while loading shared libraries: libkemoticons.so.4: cannot open shared object file: No such file or directory
Now, konsole, firefox, and Chromium's errors are a little different.
Konsole:
Quote:
konsole: symbol lookup error: /usr/lib/libphonon.so.4: undefined symbol: _ZN9QMetaType15registerTypedefEPKci
Firefox and Chrome basically say the same thing
Quote:
/usr/lib/firefox-3.6.13/firefox-bin: symbol lookup error: /usr/lib/mozilla/plugins/skypebuttons.so: undefined symbol: _ZN9QListData11detach_growEPii
again, I am completely baffled here, as I had kate, konsole and ark running before I upgraded to -current.
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Mar 16, 2010
I want to run blender in Ubuntu910,but get below
test@ubuntu:~$ blender
blender: error while loading shared libraries: libpython2.5.so.1.0: cannot open shared object file: No such file or directory
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Feb 4, 2011
how come shared memory is only using 4 gigs of ram?
Code:
localhost router # free -m
total used free shared buffers cached
Mem: 8001 858 7142 0 130 235
-/+ buffers/cache: 492 7508
[code]...
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Apr 20, 2010
I am trying to troubleshoot an Apache/Mysql server that once every few days falls over due to memory starvation. I thought I had tuned my httpd.conf file with relativley small MaxClients and so on, but then noticed some unusual RES values in top while monitoring.
In short, `top -b -n1 -u apache` shows that I have 28 httpd processes. their VIRT is ~300MB for each process (I understand this is shared), and the RES ~50MB for each. I thought this wasn't shared. Is this true? I just noticed 2 of the processes jump to 1.2g. If RES represents non-shared memory then concievably 1.2g x 28 processes would be a problem on an 8GB server.
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Jul 16, 2010
Does anyone know if there is a size limitation for shared-memory segments in RHEL AS 4?
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Aug 13, 2010
I have two partitions: one for Ubuntu 64-bit and another one with the format NTFS only for keeping documents. I have shared one folder of this NTFS partition, but every time I reboot the PC (or shutdown and start again for that matter) the folder is no longer shared.Why?How can I prevent this folder to be un-shared when I reboot the computer?
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Apr 5, 2010
I'm running a Debian based distro.
When I run ipcs this pops up:
This happens only while KDE3 is running. Regardless of the runlevel, if kdm is not started, this will not show.
By running ipcs -p the PID points to process
Is there anything wrong with that command?
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Aug 20, 2010
When I boot into Linux i see some shared memory which is blocked, due to this I am unable to start my processes which needs some shared memory.I tried removing the shared memory using ipcrm -m but no use, the shared memory is not cleaned but its still in use.I tried removing the shared memory using root user also normal user but unable to remove the shared memory.
[pin01]$ ipcs -m
------ Shared Memory Segments --------
key shmid owner perms bytes nattch status
[code]...
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May 7, 2010
I have to figure out how to pass data between a Fortran application and a C++ application. The memory has to be locked/unlocked to prevent data corruption. I know very little about Fortran. I have done mutex lock/unlock stuff in Linux apps, multi-threaded, using mutex locks before.
Digging around on the Web, I do not find any info on a Fortran app including linux headers, library calls such as those in ipc.h, shm.h and sem.h. What is an approach to this problem?
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Aug 13, 2010
When the systen is running there is a program/utility/kernel-driver? kthreadd in system monitor all the following programs are a child process of kthreadd. Is kthreadd part of elevator=cfq and can kthreadd be influenced by params. kthreads uses no cpu time memory or shared memory so it must be in kernel. is there any documentation on this subject? System 11.3 on quad processor 8 gb mem nvidia-card and driver.
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Jul 17, 2011
How do I change the size of the available shared memory on Linux?evidently 4GB is not enough for what I am doing (I need to load a lot of data into shared memory - my machine got 8GB of RAM).
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May 17, 2011
My problem is I installed Zone Minder for camera security and I'm testing it on my laptop with the built in webcam and everything seems to work perfectly except when I try to view the live feed from the camera, it's just a black box. No video.
I checked this website and it's exactly the problem I'm having with a fix for it but his fix doesn't work. He says to type:
Code:
user@ubuntu:~$ sudo echo "256000000" > /proc/sys/kernel/shmmax
user@ubuntu:~$ sudo service apache2 restart
user@ubuntu:~$ sudo service zoneminder restart
But when I do the first line, I get this:
Code:
deemar@Clementine:~$ sudo echo "256000000" > /proc/sys/kernel/shmmax
bash: /proc/sys/kernel/shmmax: Permission denied
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Jan 12, 2010
I just opened an (unmanaged) VPS account and and have been encountering nothing but problems with trying to get Apache up and running (its something I've done many times before).Basically the inital error was with LDAP not having enough space, so I disabled the related extensions and Apache still would not run. Looking at the log, it contains: (28)No space left on device: Unable to create scoreboard (anonymous shared memory failure)
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Nov 30, 2010
I need to find the memory usage of a shared library loaded in Linux environment.
I need this information for deciding on whether to make the library part in to application or a seperate application itself.
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