pthread_create argument changes

Question

I'm experiencing that the argument passed to new thread are corrupted.

static int hm_create_zone_thread(zone_threads_t *zone_thread) {
    int ret;
    int ret_val;
    pthread_attr_t attr;

    ret_val = OK;

    ret = pthread_attr_init(&attr);
    if (ret != 0) {
        debug(hm->dbg, DEBUG_ERR, "%s(): Error creating thread_attr for zone '%" PRIu64 "': %s.\n", __func__, zone_thread->id, strerror(ret));
        ret_val = ERR;
        goto return_point;
    }
    ret = pthread_attr_setstacksize(&attr, hm->stack_size);

    if (ret != 0) {
        debug(hm->dbg, DEBUG_ERR, "%s(): Error setting stack for zone '%" PRIu64 "': %s.\n", __func__, zone_thread->id, strerror(ret));
        ret_val = ERR;
        goto return_point;
    }

    ret = pthread_create(&zone_thread->thread, &attr, hm_start_zone, zone_thread);
    if (ret == 0) {
        /* Zone thread started successfully*/
        usleep(1000);
    } else { /**/
        // TODO!!! Log error, but keep creating other threads.
        debug(hm->dbg, DEBUG_ERR, "%s(): Error creating thread for zone '%" PRIu64 "': %s.\n", __func__, zone_thread->id, strerror(ret));
        ret_val = ERR;
    }

    pthread_attr_destroy(&attr);
    return_point:
    return ret_val;
}

When I debug my code, I see that zone_thread points to some sensible area, and when hm_start_zone() is executed, it gets completely different pointer value. My program then gets segfault, hence the pointer points to non existing memory.

    Breakpoint 1, hm_create_zone_thread (zone_thread=0x5555555cbfb0) at /home/lev/git/lbms/host/home_manager/hmd/src/hm.c:190
190     ret = pthread_create(&zone_thread->thread, &attr, hm_start_zone, zone_thread);
(gdb) n
[New Thread 0x7ffff7fcb700 (LWP 55270)]

Thread 2 "hmd" received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7ffff7fcb700 (LWP 55270)]
0x000055555555e190 in hm_start_zone (arg=<error reading variable: Cannot access memory at address 0x7ffff7fab198>)
    at /home/lev/git/lbms/host/home_manager/hmd/src/hm.c:215
215 static void *hm_start_zone(void *arg) {
(gdb) 

It is interesting that if I replace the &attr from the pthread_create() call with NULL, everything works fine. I certainly don't want to do that.

Edit:

The code that calls hm_create_zone_thread() is as follows:

int hm_start_zones(void) {

    int ret, ret_val;
    static char condition[1024];
    zone_t zone;
    zone_threads_t *current_zone_thread;


    ret_val = OK;

    sprintf(condition, "stat=%d", hm_zone_enabled);

    zone.data_state = db_data_init;
    while (zone.data_state != db_data_last) {
        ret = db_query_zone(hm, &zone, condition);
        if (ret != OK) {
            ret_val = ERR;
            break;
        }
        if (zone.data_state == db_data_valid) {
            /*Add a new member to the chained list*/
            hm_lookup_zone(zone.id, &current_zone_thread);
            if (current_zone_thread != NULL) { /*already created*/
                /*TODO!!! What to do if the zone is there, but it is stopped, or in error state?*/
                continue;
            }
            ret = hm_add_new_zone(zone.id);
            if (ret == ERR) {
                ret_val = ERR;
                break; /*Give up*/
            }
        } else {
            break; //No more zones in the database.
        }
    }

    /*Start zones*/
    for (current_zone_thread = zones_head; current_zone_thread != NULL;) {
        hm_create_zone_thread(current_zone_thread);
        current_zone_thread = current_zone_thread->next;
    }

    /*TODO!!! Check for stopped zones*/

    return ret_val;
}

Answer 1

Solved by enlarging the stack size to 8MB. I originally set the stack to 2*PTHREAD_STACK_MIN. This is strange.