#include <stdlib.h>
#include <stdint.h>
#include <unistd.h>
#include <string.h>
#include <pthread.h>
#include <stdio.h>
#include <errno.h>

void alloc_and_die(void)
{
    uint64_t i;
    uint64_t n = 4*1024*1024*1024ll;
    char *x = malloc(n);
    printf("touching pages\n");
    /* touch each page once */
    for (i=0;i<n;i += 4096) {
	x[i] = 42;
    }
    /* wait a bit */
    printf("sleeping\n");
    /* parallel coredump */
    fork();
    sleep(10);
    printf("Dumping core...\n");
    /* now die */
    abort();
}

void *iothread(void *dummy)
{
    uint16_t data[4000];
    char fname[128] = "iothreadXXXXXX";
    unsigned int seed = 0x42;
    unsigned i;
    uint64_t pos = 0;
    unsigned counter = 0;

    int fd = mkstemp(fname);

    if (fd == -1) {
	perror("mkstemp");
	abort();
    }

    for (i=0;i<sizeof(data)/sizeof(data[0]);i++) {
	data[i] = rand_r(&seed);
    }
    /* continously write to a 1MB sized file */
    while (1) {
	if (write(fd, data, sizeof(data)) != sizeof(data)) {
	    perror("write failed");
	    abort();
	}
	pos += sizeof(data);
	if (pos > 10*1024*1024ll) {
	    counter++;
	    if (counter%2) {
		fsync(fd);
		lseek(fd, 0, SEEK_SET);
	    } else {
		unlink(fname);
		close(fd);
		strncpy(fname, "iothreadXXXXXX", sizeof(fname));
		fd = mkstemp(fname);
		if (fd == -1) {
		    perror("mkstemp");
		    abort();
		}
	    }
	    for (i=0;i<sizeof(data)/sizeof(data[0]);i++) {
		data[i] = rand_r(&seed);
	    }
	}
    }

    return NULL;
}

void run_iothread(void)
{
    pthread_t thr;
    int rc;
    rc = pthread_create(&thr, NULL,
			iothread, NULL);
    if (rc) {
	errno = rc;
	perror("pthread_create");
	abort();
    }
}

int main()
{
    switch (fork()) {
	case 0:
	    run_iothread();
	    run_iothread();
	    alloc_and_die();
	    break;
	case -1:
	    perror("fork failed\n");
	    abort();
	    break;
	default:
	    run_iothread();
	    run_iothread();
	    run_iothread();
	    run_iothread();
	    iothread(NULL);
	    break;
    }
    return 0;
}