3 threads problem

[lectrolux]

hi,

I have 3 threads in my program but without mutex. Now the problem is that the 3th thread stops looping...

Do I have to use mutex and how does it work for 3 threads

static char buffer[64][255]
static char buffer2[30][3000]

/* in the main */

iret1 = pthread_create(&thread1,NULL,(void*)&read_port,NULL);
			iret2 = pthread_create(&thread2,NULL,(void*)&read_buffer,NULL);
			iret3 = pthread_create(&thread3,NULL,(void*)&split_buffer,NULL);

			pthread_join(thread1,NULL);
			pthread_join(thread2,NULL);
			pthread_join(thread3,NULL);

/* thread 1 */

for(EVER){
		res=read(fd,buf,255);
		buf[res]=0;
		
		if(res > 0){

			strcat(buffer[i],buf);

			i++;

			if(i==64){
				i=0;
			}

		}
	}

/* thread 2 */

for(EVER){
	if(a!=i){
                         /* here i get data out of first buffer and put it into second buffer */
                }
}

/* thread 3 */

for(EVER){

		if(j!=c){
                                   /* here i read from the second buffer, split it in pieces and write to database */
                                 }
}

[lectrolux]

Originally posted by Salem
Since thread 1 has a buffer overflow, I'd fix that first
there is no overflow
http://www.cs.cf.ac.uk/Dave/C/CE.html
Lots of info on threads / shared memory

thx for the url

greetz

[lectrolux]

Originally posted by vVv
First, in main( ) you can call pthread_exit( ) instead of pthread_join( )'ing all threads.

I don't know the purpose of thread 2, but it looks like you're having some redundant overhead by copying the data twice - does thread 2 change / add to the data? Mutexes will work just fine - check out pthread_mutex_lock( ) / pthread_mutex_unlock( ). And you can use condition variables to put threads asleep until data is available (needed perhaps if ``fd'' is a pipe or socket and might not immediately return data) - check out pthread_cond_wait( ) and pthread_cond_signal( ).
(Search the board, I posted several snippets using these functions in the past)

the purpose of thread 2 is to get al data out of the first buffer and put them into buffer2, in buffer2 the data becoms al whole message and then ion thread 3 I can search for a date , an hour in the messages.

the program works but at a given moment the last thread just stops writing to database, the first and the second are still running

thx