Programming :: How To Communicate Between Two Threads Using Message Queue
Jun 7, 2011How to communicate between two threads using message queue?
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Programming :: Posix Message Queues - Communicate Between Two Threads?
Jan 3, 2011I want to communicate between two threads, each belonging to a different process. Iam using message queues for this. I use mq_open()call. I created the queues with the same queue name starting with a '/'. But when I open the queue, the queue ID is different in both the process. What should I do so that both the process have the same queue ID?
View 1 Replies View RelatedProgramming :: Block Messages On A Message Queue ?
Dec 3, 2010I'm facing a scenario in which i need to block messages from being passed onto a message queue when my code is running. how to proceed.
View 8 Replies View RelatedProgramming :: Theoretical Limit On Message Queue Sizes ?
Jun 4, 2010Following function obtains the system-maintained structure for a message queue:
Code:
And following function simply resizes a message queue to a user-defined value, namely, "size":
Code:
My question is if there is a theoretical limit on user-defined message queue sizes.
To put in other words, is it possible to increase the default message queue size to any user-defined value as long as that certain value does not exceed the size of system's physical memory ?
I use 64-bit Ubuntu 9.04.
Programming :: Program Hang Stuck There Signal Handling On POSIX Message Queue UNIX C Pr
Jun 14, 2011In a single main() function,so need signal handling. Use Posix Message Queue IPC mechanism , can ignore the priority and other linked list message,to implement the scenario:
View 1 Replies View RelatedProgramming :: Get Length Of Run Queue And Swap Queue?
Nov 3, 2010is it possible to get the length or even the items of both queues, the run queue and the swap queue? I've googled a lot but had no luck. Maybe I havn't used the correct search words...
Is there any header and/or code example to use structures or any API to get these information from the kernel or the scheduler?
Networking :: Error Message - Can't Communicate With Ypbind
Apr 6, 2010I am trying to set up an NIS client on a Fedora Core 12 64-bit system. The ypbind daemon is running via the /etc/init.d/ypbind script. However, whenever I run the ypwhich command, the following error message appears on-screen:
[code]...
The client has been configured so the domain is set, and the client will broadcast for the first available nis server. The client is on a subnet where there is one nis slave server, so it should bind to that server. One thought that came to mind was the fact the client in question is 64-bit, while the nis slave is 32-bit. Could that cause this problem?
Programming :: Unix Programming - Single Process That Does Not Start Up Any Other Threads
Sep 28, 2010i want a process that can operate as both a TCP echo server and a UDP echo server. The process can provide service to many clients at the same time, but involves a single process that does not start up any other threads.
View 3 Replies View RelatedProgramming :: Communicate To RS232 Using Fstream?
Apr 1, 2009I'm trying to attach an fstream to serial port for reading and writing with the following code:
Code:
#include <iostream>
#include <fstream>
#include <string>
[code]....
The code compiles without errors, but doesn't catch any input text from the device attached to RS232. I have tried it with Rx and Tx connected, but didn't receive my text back. It works OK if I substitute /dev/ttyS0 with an ordinary file, but any attempt to use /dev/ttyS0 seems to lead to an empty answer string. I tried this on a PC under Ubuntu Linux 7.10.
Programming :: Possible To Communicate Values Between Class?
Feb 24, 2009I have a application in C++, and now I have two class. MyDialog is the class that main function launch. In MyDialog class there are four elements and when I click over theese elements, there is a MousePressEvent that launch other class, Touchpad class. So, in some moments, I have loaded two class. My question is, how can pass a value from Touchpad class to MyDialog class, when I close (destroy) Touchpad class. In a few words, is it possible to communicate values between class?
View 5 Replies View RelatedProgramming :: How To Run The Threads Continuously
Dec 1, 2010I have two threads & i want to run it continuously ,with while(1) it is possible . Is there any other way to run the threads continuously
View 12 Replies View RelatedProgramming :: Server With 2 Threads Per Client?
Nov 25, 2010In all the examples I have found the server accepts the client's conection, proccess the data received and close the socket. In an very schematic way it would be something like:
Code:
client_thread{
select to see if there is data to read from socket fd
if there is something to read{
[code]....
Should I use mutexs or semaphores to block the socket fd before read and write or it is not necesary?
Programming :: Listing All Threads In A Process?
Dec 29, 2010How to list all the threads spawned by a process?
View 4 Replies View RelatedProgramming :: Threads Not Getting Arguments Properly
Mar 26, 2011I wrote a C program using Pthreads to compute the product of 2 matrices. Each element in the product matrix is computed in a separate thread. Eg: Thread (i,j) computes the element C[i][j] of the matrix C, where C=A*B. A is m*n, B is n*p, C is m*p. m,n,p are given as command-line arguments. A and B are initialized to random values from 1 to 10, while all elements of C are initialized to -1.But some threads do not get their arguments (i,j) correctly. So some elements C[i][j] still remain as -1, even after the program is over. My OS is Ubuntu 10.10 (Maverick Meerkat) 32-bit.I ran the program on another computer and it worked correctly. Is it due to a problem in the Pthreads library in my OS? Please help me. I have attached the source code.
View 3 Replies View RelatedProgramming :: CPU Sharing Between Process And Threads?
Mar 29, 2011I have doubt regarding cpu sharing between process and threads.In my program iam creating 4threads=> 1 process+4 threads. How is cpu alloted to these all tasks. Is here process is getting cpu time like thread or having more cpu time than threads.
View 1 Replies View RelatedProgramming :: Data Transfer Between Threads?
Dec 14, 2010In posix multi threading, how to send thread1 local data to thread2...?
View 3 Replies View RelatedProgramming :: Multiple Threads In Socket C++?
Nov 26, 2010Code:
void* thread(void* arg)
{
[code]....
Programming :: Synchronize 2 Posix Threads ?
Mar 15, 2011I have 2 threads and both of them are deleting memory at the end nedded by both.
My problem is that maybe it can happen that a thread start and finish before the other one starts and so it deletes the memory nedded by the other thread. How can I synchronize them so that this can't happend.
As a design my threads look like this:
Code:
The other thread looks the same, but this isn't unoff to stop thread1 to finish before thread2 starts.
Programming :: Code Of Merge Sort With Threads In C?
Feb 17, 2011Please I want Know the code of the Merge Sort with threads in C
View 7 Replies View RelatedProgramming :: Command For Seeing Number Of Threads Running?
Jun 8, 2011IS there any command to see number of threads are running in a process .I have check ps -eLf but it wont show display for all the threads
View 1 Replies View RelatedProgramming :: Reduce Memory Cost Of Threads?
Jul 21, 2011Fedora15 32bit. I write a test program, it creates new thread continually, the thread does nothing but sleep. I find virtual memory increases up almost 10Mb when a new thread is created. and when there's more than 200 threads, the virtual memory used by the program is 3Gb, and now cann't create new thread. but on windows, it costs little memory. What can I do to config the operation system to take less memory on threads?
View 11 Replies View RelatedProgramming :: Timings Of A Program That Uses 1-8 Threads On A Server That Has 4 D?
Jul 25, 2010I am runig a program on a server at my university that has 4 Dual-Core AMD Opteron(tm) Processor 2210 HE and the O.S. is Linux version 2.6.27.25-78.2.56.fc9.x86_64. My program implements Conways Game of Life and it runs using pthreads and openmp. I timed the parrallel part of the program using the getimeofday() function using 1-8 threads. But the timings don't seem right. I get the biggest time using 1 thread(as expected), then the time gets smaller. But the smallest time i get is when i use 4 threads.
Here is an example when i use an array 1000x1000.
Using 1 thread~9,62 sec, Using 2 Threads~4,73 sec, Using 3 ~ 3.64 sec, Using 4~2.99 sec, Using 5 ~4,19 sec, Using 6~3.84, Using 7~3.34, Using 8~3.12.The above timings are when i use pthreads. When i use openmp the timing are smaller but follow the same pattern.I expected that the time would decrease from 1-8 because of the 4 Dual core cpus? I thought that because there are 4 cpus with 2 cores each, 8 threads could run at the same time. Does it have to do with the operating system that the server runs?
Also i tested the same programs on another server that has 7 Dual-Core AMD Opteron(tm) Processor 8214 and runs Linux version 2.6.18-194.3.1.el5. There the timings i get are what i expected. The timings get smaller starting from 1(the biggest) to 8(smallest excecution time).The program implements the Game of Life correct, both using pthreads and openmp, i just cant figure out why the timings are like the example i posted. So in conclusion, my questions are:
1) The number of threads that can run at the same time on a system depends by the cores of the cpus?it depends only by the cpus although each cpu has more than one cores? It depends by all the previous and the Operating System?
2) Does it have to do with the way i divide the 1000x1000 array to the number of threads? But if i did then the openmp code wouldn't give the same pattern of timings?
3)What is the reason i might get such timmings?
Programming :: Proper Implementation Of POSIX Threads
Apr 6, 2011I've implemented a program URL... which reads digital IF data from a radio receiver through a named pipe, measures power levels, and sends the result to stdout. The program is interactive; there is a thread that reads from stdin to watch for commands, a thread that constantly either reads data from the named pipe or throws data away, and an array of processing threads. The program uses GTK+extra to plot the signals. The IF data stream bandwidth exists at the limits of today's technology (is very very fast).
Problem Statement:The program works fine with a few bugs. I've learned since I've made it that using global state variables to coordinate threads isn't a good way of doing it. I also only had knowledge of mutexes and polled the state variable instead of using other methods.My reimplementation will use the following:
- One "Stdin Command Monitoring" thread
- One "Get data from named pipe" thread
- One post-processor thread
- N Processing threads
All threads are alive during the life of main()There are N buffers. Data will come in from the named pipe, and the "Get data" thread will write the data to an "available" buffer. When the buffer is full it will be marked as "full". There will be N processing threads, one for each buffer. When a processing threads' buffer is full, it will process the buffer and save the result to a final buffer. At the end of a number of averages, the post-processor thread will perform a final process on the final buffer and send the results to stdout.
Programming :: Good Book To Learn About Threads In C / C++?
Oct 30, 2010A good book to learn about threads in C/C++?
View 3 Replies View RelatedProgramming :: Mutexes Necessary - Gets Locked / Unlocked Each Time One Of The 60 Threads?
Jun 24, 2011I'm a bit worried about "too many mutexes" in my little curses-based app and would like to get confirmation/opinions that I'm doing this right. I've got an array: int nums[60] I've got 61 threads. 1-60 are doing math on the value in their array index (ie: thread1 increments nums[1], threadN increments nums[N]), then sleep(1) The 61st thread is my curses thread which does a for-loop over the array and prints out all the values to the screen, then sleep(1)
Right now, I've got 1 mutex which gets locked/unlocked each time one of the 60 threads needs to update its array-index with a new value, and the 61st thread locks the same mutex just before the for-loop beings reading the values and unlocks after ending the loop.
My questions:
A) Does the above seem OK? (I know it's ok, cause everything works right now but would like opinions on it)
B) Do I even need the mutexes since 1-60 only ever update their own index and 61 just reads?
C) If I do need the mutex protection, is there a better, more efficient way?
Programming :: Synchronization Between Threads Fails - Resource Unavailable
May 6, 2009I am working with a C++ program consisting of two threads. The first threads receives packets through an UDP unicast connection and stores them in a buffer. The second thread reads the packets from the buffer and sends them through an UDP multicast connection. Both use blocking sockets and share a common buffer and a linked list L1, which are protected by mutexes. The program seemed to work just fine, receiving a packet and sending it almost immediately, but started giving some trouble recently. The synchronization between both thread started failing, and I decided to use a non-blocking socket in the sending thread. As a consequence, sendto() doesn't work in some cases, causing an errno 11 (Resource unavailable).
[Code] ...
Programming :: Find Number Of Threads In The Process In C Language?
Dec 23, 2009I need to find how many threads are alive with respect to the current process for my further processing. Is there any means to trace this number ?[URL]I referred the above link. But sys/pstat.h is not in my system. Don't know which library gives this header.
View 14 Replies View RelatedProgramming :: Can Two Threads Safely Work On A Linked List Without Locking
Nov 9, 2010I have a linked list that two threads work on simultainiousley.The first thread is adding elements to end the linked list while the second is removing them from the front. Can this be done without a lock on the linked list head when elements are beingadded/removed?
I think this lock is causing a performance hit to my application. If there isnt any safe way without it then thats fine but just thought I would check.The first thread uses this fuction to add elements to the list. Full source here. [URL]
Code:
/* Lets add the new packet to the queue. */
pthread_mutex_lock(&workers[queuenum].queue.lock); // Grab lock on queue.
if (workers[queuenum].queue.qlen == 0){ // Check if any packets are in the queue.
[code]...
Programming :: C Code Profiling Technique That Supports Multiple Threads?
Mar 8, 2011I am using GPROF for my code profiling ,but it seems GPROF doesn't supports multithread .Does any one know any other technique for profiling the application code I have checked oprofile but it profile kernel ,I just required for C code profiling technique that supports multiple threads
View 1 Replies View RelatedProgramming :: Pthread - Optimize Computing Function / Loop With Threads?
Sep 4, 2010I have to compute prime numbers with threads in C. So I choose the algorithm "Sieve of Eratosthenes" and I tried to create 2 threads, but I don't know how to optimize my computing function with threads I beg for help. This is my function:
[Code]...
but it seems like the both of the threads are calculating the same function twice? Is it possible to be optimized or not?