C :: Consumer And Producer Threads Aren't Synchronizing Correctly?
Dec 3, 2013
I have a school assignment to create a program that uses a producer thread to create a series of random numbers, and a consumer thread to read those numbers (via a shared bounded buffer), and record the min, max, average, and number of items. Now, the threads aren't synching well. Here's my code:
I am working on the producer-consumer problem and am mostly happy with what I have except for one remaining issue. I am using pthreads for consumers and producers on a FIFO, and synchronizing using a combination of semaphores and mutexes. Things seem to work fine, except that my consumers seem unable to tell when there may be more data coming into the FIFO.
I need to be able to determine not just when the FIFO is empty (it gets emptied every time a consumer thread runs) but when ALL producers have detached from it - that's when my consumers should pthread_exit, and not before that. I have read conflicting information on how FIFOs work in terms of EOF and have been unable to get it working.
(NOTE: that's what I *think* the problem is... It's my first time working with pthreads, so there may be other issues I am not even aware of).
In any case, my code is below. I am running it on a Linux VM on top of Windows, if that makes any difference. It takes 3 command line parameters - FIFO name (will be created if doesn't exist), number of producers, and number of consumers.
I have a program to make a contact book. Included below i will post both header files and cpp files of my contact book, my contact class, and my address class. and my main.cpp. The reason address and contact are separate was because my teacher had us do an exercise where we used a header file of someone else's code, and didn't know what the functions actually implemented. But as the project has progressed he gave us the cpp for address.
Right after I close FIFO on the producer side, the app on the consumer side gets into an endless loop. select() returns that FIFO is ready to read. Below is the excerpt from the consumer code. The FIFO is opened "blocking" on both ends.
I found this program in a forum and it creates 1 to t threads with each thread pointing to the next and the last thread pointing to the first thread and it allows each thread to sequentially take a turn until all threads have taken n turns. That is when the program ends.
My doubt is if we see in void *tFunc(void *arg) function, first thread locks the mutex and then wait there forever till it's turn comes.Lets say if I spwan 1000 threads and they have take 10 turns each sequentially and what if a 550th thread locks the mutex as soon as the program starts and waiting for its turn which will never happen because still (turn=1) which means it's first thread's turn and first 549 threads have to complete their 1st turn before this 550 threda's turn comes.Doesnt this result in deadlock?
The problem is i don't want to use local vars , is ther anyway do end the loop safely(removing all the vars used in function and etc) without using a local var ?
I had a requirement where i needed to create a thread and if the execution of thread is not completed in 5 minutes i needed to terminate its execution and continue with other part of the code.
I used the below code to create the thread
_beginthread(FuncnCall,0,NULL);
HANDLE hThread = GetCurrentThread();
Then after this code, I used the below code to check for 5 minutes
for (int i=1;i<=0;i++) { printf("Value of i=%d ",i); if(threadFinished) { break; } else { Sleep(1000); } }
After this if the value of "threadFinished" is false then i am terminating the thread like below
The Problem here is, after terminating the thread, the program abruptly closes by giving fatal error. Looks like memory leakage is happening after terminating the thread. Is it not the right way to safely exit the thread?
I am on a little project involving TCP socket-programming and multiple threads but need passing structures between two threads.
The first thread receives data with respective ID, temp, etc,.. Each ID is a list-item of a linked list and every ID has again a linked list of all the received data.
The second thread just have to access the list and perform some manipulations on it.
My solution: pass the head pointer of the linked list. Easy enough, right? Somehow, I am stuck receiving error message:" dereferencing pointer to incomplete type."
For the sake of ease and simplicity I just added a stripped down version of the project.
The magic (or not) happens in MainProcess.c: The Data thread should receive the pointer (a think) from the Connection thread.
I am doing something wrong since for me 4 threads perform 2 times slower then 1.I have 2 vectors with bunch of data to process, there is no concurrency (not moving elements and are independent of each other) so i just need to calculate some data from one and copy result in another.
I want to create two threads which will be calling even and odd functions where even function should print even number and odd function should print odd number.Can it be possible with condition variable? What is the code in both the cases i.e. two separate function and with condition variable.
how do I stop and restart a Thread in C# once it reaches a certain location on a form then restart the thread once it goes outside of the location boundries?
I am trying to stop an animation thread (a bullet) once it reaches a block on a panel.
void Arrival_MainThread::Body () { t1 = new boost::thread((Arrive_Fctor()), 2); t2 = new boost::thread((Arrive_Fctor()), 10000); t3 = new boost::thread((Arrive_Fctor()), 3000);
Code: class Arrive_Fctor { public: void operator()(int mean) { m_Arrivals = new Arrivals(mean); m_Arrivals->Activate(); #ifndef NO_RESOURCE
[code].....
The order of arrivals always appear as 3,2,1 it can't be 1,2,3 or 3,1,2 or something like that?
The body method is called when m_Arrival->Activate() is executed, and it is running as an independent thread.
Although MyThread1 and MyThread2 using critical section to protect the shared data m_Data, I will still suspend MyThread1 before accessing the shared data, to prevent any possible conflicts.
The problem is:
(1)When the first invoke of MyFun2, everything is OK, and the return value of MyFun2(that is nResult2) is 1 , which is expected.
(2)When the second, third and fourth invoke of MyFun2, the operations in MyFun2 are executed successfully, but the return value of MyFun2(that is nResult2) is a random value instead of the expected value 1. I try to using Debug to trace into MyFun2, and confirm that the last return statement is just return a value of 1, but the invoker will receive a random value instead of 1 when inspecting nResult2.
(3)After the fourth invoke of MyFun2 and return back to the next statement follow MyFun2, I will always get a "buffer overrun detected" error, whatever the next statement is.
I think this looks like a stack corruption, so try to make some tests:
1.I confirm the /GS (Stack security check) feature in the compiler is ON.
2.If MyFun2 is invoked after MyFun1 in MyThread1 is completed, then everything will be OK.
3.In debug mode, the codeline in MyFun2 that reads the shared data m_Data will not cause any errors or exceptions. Neither will the codeline in MyFun1 that writes the shared Data.
I have a vector that I would like to access and work with from multiple threads. I have created an example below to illustrate the functionality that I would like to accomplish.
The goals are to be (1) high speed, (2) thread safe, and (3) *if possible* continue to use vectors as my larger project uses vectors all over the place and as such I would like to maintain that.
However, if I need to switch from vectors to something else then I am open to that as well.
The following example below compiles but crashes rather quickly because it is not thread safe.
How I can fix the example below which I can then apply to my larger project?
I am trying to write a code that solves a system of linear equations such as A*B=C. My system has a dimension equal to 1600. The matrix A cab be separated into 4 sub matrices and each can be handled by a different thread. I tried to solve this using the following code:
int main() { int count = 0; //Inputing matrix A ifstream matrix; matrix.open("example.txt");
[Code] ....
Although the above code gives the correct answer, the time needs to find the solution is bigger than that needed without using threads.
I'm currently working on a server for handling clients in a 2d online game and I wrote some regular fstream file code for handling the file that stores their information and I was about to implement it into the server, then I realized there might be a problem having it open multiple times concurrently, so I googled it and came up with posts like
[URL]
I'm wondering if I can just treat it like everything else or will I have to do something specific for opening on multiple threads?
p.s. I did read those posts but I'm very new to multithreading
In my program, after menu when he selects a choice, next display of menu wait the termination of the selected thread. while i want to show menu right after when a menu is selected.
so i have this problem with my code ( not running)i want to read ( 2 double numbers x,y) and ( one integer z) then calculate reminder of x and y ( after they both converted to integer) and the formula : x^2 + y^2 + z^2and : x^z + y^z
here is what i came up with :
Code: // compute.c
#include<stdio.h> #include<math.h> int main(void) {
[Code]....
it also says in q : be sure to test the user input to make sure x,y,z are positive . any negative or zero should not be accepted and must print error msg ==> do i have to have an if statement here ? or the while loop is enough ?
I'm writing a version of the classic Snake game. However, my board is not printing correctly. The right hand border is in the incorrect location. Also, when I randomly generate where the food ('X') is located, it only generates on the edges of the boundaries.
#include <iostream> #include <cstdlib> using namespace std; const int ROWS = 21; constint COLS = 61;
