POSIX - Hot to check if detached thread is still active

[orangem]

Hello,

I have created program that run threads one by one, maximum 100. Each thread will process one block of data, and once it`s finished, new thread is created with new block of data....etc

I have array of values to control status of each thread, like this:

array_thread_status[0]=1
array_thread_status[1]=0
array_thread_status[2]=0
array_thread_status[3]=1
...
array_thread_status[99]=1

When thread is created value is set to 1. When thread is finished, it set value to 0, so main program can create new thread instead.

This is all working good, so far...but I`m affraid of this scenario:

Main program
CREATE THREAD
SET VALUE TO 1


Thread
STARTING THREAD
PROBLEM - THREAD IS TERMINATED AND DIDN`T RESET VARIABLE TO 0

Main program might think that thread is still active, and new one will not be run.

So, I think that there must be another way to check weather thread is still active or not.

[jim mcnamara]

Try pthread_join

[orangem]

it`s detached thread

[jim mcnamara]

How are you creating the detached threads ... please show your code.

[orangem]

/*Mark it active*/
active_status_array[i]=1;

/*Create new threads*/
rc = pthread_create(&thdreads[i], &attr, file_parser, (void*)&thread_data_array[i]);

if (rc)
{
printf("ERROR; return code from pthread_create() is %d INDEX %d\n", rc,i);
exit(-1);
}
else
{
/*Deatach thread*/
rc = pthread_detach(thdreads[i]);
if (rc) {
printf("Got an unexpected result! rc=%d\n",rc);
exit(-1);
}

}

[orangem]

Also, one more problem with join is that if I have 100 threads, and if they are all working and I start join wait on first one which is wait 5 min, for example. during that time other might be free...so that could slow down entire program.

My main program never ends, it`s always iteratting trought the loop and checking for free space to create new threads.

[jim mcnamara]

I think you have a need for synchronization - meaning you do not want detached threads.

Here's why - On most systems the "thread" is really a part of the parent process - linux is an exception. This means generally there isn't a simple way to tell if a thread has terminated. If you need to know the status of a thread then you need synchronization.
Correct me where I misunderstand.

Otherwise, detached threads run whether or not the previous thread completed or not.
This is the exact opposite of synchronization.