User:Kr/A Thread's Life

Status: draft

Two types of Threads

• holder threads
• holded threads

Holder Thread

• Holder threads keep the process alife.
• The last holder thread terminates the process.
• Every holder thread must be detached, as no other thread is going to join it.

Examples

• GUI dispatcher thread

Holded Thread

• Holded threads don't keep the process alife.
• Any holded thread needs to be joined (terminated / cancelled) when (indirectly) released by a holder thread.
• Every holded thread must be joinable, as a holder thread is going to join it, latest during termination.

Examples

• cache flushing threads

Notes

• Threads may dynamically switch from one type to the other and vice versa.
• The "main" thread is a holder thread.

[cpp]

1. include <stdlib.h>
2. include <stdio.h>
3. include <pthread.h>

static void * holder(void * gr) {

   fprintf(stderr, "%s - tid: %x\n", __PRETTY_FUNCTION__, pthread_self());

   sleep(5);

   if (1) // This may only be true if this is the last "holder" thread!
       exit(0);

   else
       pthread_exit(NULL);

}

static void createHolderThread() {

   pthread_attr_t attr;
   
   pthread_attr_init(&attr);
   pthread_attr_setdetachstate(&attr, 1);
   
   pthread_t bt;
   pthread_create(&bt, &attr, holder, NULL);
   pthread_attr_destroy(&attr);

}

static void * holded(void * gr) {

   fprintf(stderr, "%s - tid: %x\n", __PRETTY_FUNCTION__, pthread_self());

   sleep(10);

   pthread_exit(NULL);

}

static pthread_t hd;

static void join_holded(void) {

   fprintf(stderr, "%s - tid: %x\n", __PRETTY_FUNCTION__, pthread_self());

   // You may want to cancel a thread actively during termination:
   pthread_cancel(hd);
   // respectively
   //pthread_kill();

   pthread_join(hd, NULL);

}

static void createHoldedThread(void) {

   pthread_create(&hd, NULL, holded, NULL);
   atexit(join_holded);

}

static void print_something(void) {

   fprintf(stderr, "%s - printing ... tid: %x\n", __PRETTY_FUNCTION__, pthread_self());

}

int main(void) {

   atexit(print_something);

   createHolderThread();

   createHoldedThread();

   pthread_exit(NULL);

   return 0;

}