Sponsored Content
Top Forums Programming Multi thread data sharing problem in uclinux Post 302399305 by Loic Domaigne on Saturday 27th of February 2010 04:15:17 AM
Old 02-27-2010
Quote:
Originally Posted by Corona688
Try 'volatile int lock'. If you're going to modify a variable out from under something else in mysterious ways like threading or memory poking, you have to tell the compiler so. Otherwise it feels free to optimize it away on the assumption that it won't change until it changes it itself.

You should really be using mutexes, though.
Yes, you should use mutex. volatile alone (along with atomic operation) is not enough to guarantee correctness in multi-threaded program. The magic word here is: memory visibility. Interested readers might want to read: Mutex and Memory Visibility

Cheers,
Loïc.

---------- Post updated at 10:15 AM ---------- Previous update was at 10:07 AM ----------

Quote:
Originally Posted by mrhosseini
thanks,


yes, that was just an example that i used to test the threads behavior.

so the mutexes and any other data that i want to be shared must be defined as volatile, am i right?
No, absolutely not. As long as you use mutex correctly, there is no need to declare the variables (or the mutexes) volatile.

On a conforming POSIX platform, the compiler shall "know" how to deal with that kind of issue as long as you follow the memory visibility rules given in XBD 4.11 of IEEE Std 1003.1-2008.

Cheers,
Loïc.

This User Gave Thanks to Loic Domaigne For This Post:
 

8 More Discussions You Might Find Interesting

1. Programming

Multi threading using posix thread library

hi all, can anyone tell me some good site for the mutithreading tutorials, its application, and some code examples. -sushil (2 Replies)
Discussion started by: shushilmore
2 Replies

2. UNIX for Advanced & Expert Users

mmap vs shared memory - which is best for sharing data between applications?

Between mmap and shared memory which is the best method of sharing data between multiple applications, interms of speed? (2 Replies)
Discussion started by: nmds
2 Replies

3. Programming

forking. sharing global data in childs

hi, i want to write a code for forking 3 4 child. n wants that every child process one of the account from global account list. i wrote a program for that, but problem is every child is processing every account in list. what can me done to avoid it. attaching code with it #include <stdio.h>... (2 Replies)
Discussion started by: anup13
2 Replies

4. Solaris

Windows/Solaris data sharing

Hi all, I have a request from Developer team in my compagny, they would like to be able to share data between unix and windows world. 1. We would like to be able to see Unix data from Windows : ?Samba ? 2 We would like to be able to see windows data from Solaris (Mount point) : ?NFS server... (4 Replies)
Discussion started by: unclefab
4 Replies

5. Shell Programming and Scripting

data sharing between process

hi ! i want to make 2 c prog such tht if i give an input in 1st prog then i can use tht input in 2nd. so over all i want to do data sharing between process using files. plz give me suggestions how can i achieve this ? thanks ya! (2 Replies)
Discussion started by: Sgupta
2 Replies

6. Shell Programming and Scripting

Multi thread shell programming

I have a unix directory where a million of small text files getting accumulated every week. As of now there is a shell batch program in place which merges all the files in this directory into a single file and ftp to other system. Previously the volume of the files would be around 1 lakh... (2 Replies)
Discussion started by: vk39221
2 Replies

7. UNIX for Dummies Questions & Answers

Cross-compiling libiconv for uclinux

Hi everyone, I want to cross-compile libiconv for uclinux to create a static library. I use the following command : ./configure --enable-static --disable-shared --build=i686-pc-linux-gnu --host=nios2-unknown-linux-gnu --prefix=/home/captain/Programs/nios2-linux/uClinux-dist/staging/usr... (2 Replies)
Discussion started by: moganesh
2 Replies

8. Shell Programming and Scripting

Multi thread awk command for faster performance

Hi, I have a script below for extracting xml from a file. for i in *.txt do echo $i awk '/<.*/ , /.*<\/.*>/' "$i" | tr -d '\n' echo -ne '\n' done . I read about using multi threading to speed up the script. I do not know much about it but read it on this forum. Is it a... (21 Replies)
Discussion started by: chetan.c
21 Replies
thr_join(3C)						   Standard C Library Functions 					      thr_join(3C)

NAME
thr_join - wait for thread termination SYNOPSIS
cc -mt [ flag... ] file...[ library... ] #include <thread.h> int thr_join(thread_t thread, thread_t *departed, void **status); DESCRIPTION
The thr_join() function suspends processing of the calling thread until the target thread completes. The thread argument must be a member of the current process and cannot be a detached thread. See thr_create(3C). If two or more threads wait for the same thread to complete, all will suspend processing until the thread has terminated, and then one thread will return successfully and the others will return with an error of ESRCH. The thr_join() function will not block processing of the calling thread if the target thread has already terminated. If a thr_join() call returns successfully with a non-null status argument, the value passed to thr_exit(3C) by the terminating thread will be placed in the location referenced by status. If the target thread ID is 0, thr_join() finds and returns the status of a terminated undetached thread in the process. If no such thread exists, it suspends processing of the calling thread until a thread for which no other thread is waiting enters that state, at which time it returns successfully, or until all other threads in the process are either daemon threads or threads waiting in thr_join(), in which case it returns EDEADLK. See NOTES. If departed is not NULL, it points to a location that is set to the ID of the terminated thread if thr_join() returns successfully. RETURN VALUES
If successful, thr_join() returns 0. Otherwise, an error number is returned to indicate the error. ERRORS
EDEADLK A joining deadlock would occur, such as when a thread attempts to wait for itself, or the calling thread is waiting for any thread to exit and only daemon threads or waiting threads exist in the process. ESRCH No undetached thread could be found corresponding to the given thread ID. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |MT-Level |MT-Safe | +-----------------------------+-----------------------------+ SEE ALSO
thr_create(3C), thr_exit(3C), wait(3C), attributes(5), standards(5) NOTES
Using thr_join(3C) in the following syntax, while (thr_join(0, NULL, NULL) == 0); will wait for the termination of all non-daemon threads, excluding threads that are themselves waiting in thr_join(). SunOS 5.10 27 Mar 2000 thr_join(3C)
All times are GMT -4. The time now is 04:23 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy