sitano

$ cat /etc/systemd/logind.conf

#  This file is part of systemd.
#
#  systemd is free software; you can redistribute it and/or modify it
#  under the terms of the GNU Lesser General Public License as published by
#  the Free Software Foundation; either version 2.1 of the License, or
#  (at your option) any later version.
#
# Entries in this file show the compile time defaults.

sitano

#include <stdio.h>
#include <unistd.h>
#include <sys/prctl.h>

int main() {
  printf("origin: pid=%d, ppid=%d, pgid=%d\n", getpid(), getppid(), getpgid(getpid()));

  printf("prctl %d\n", prctl(PR_SET_CHILD_SUBREAPER, 1, 0, 0, 0));

  pid_t pid = fork();

sitano

#define _GNU_SOURCE             /* See feature_test_macros(7) */
#include <sched.h>
#include <sys/syscall.h>      /* Definition of SYS_* constants */
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/wait.h>
#include <time.h>

sitano

docker run --rm --name pg -e POSTGRES_PASSWORD=123 -e POSTGRES_HOST_AUTH_METHOD=md5 postgres:latest
docker run --rm -e DATABASE_URL="postgres://postgres:[email protected]/postgres" -e POOL_MODE=session -p 5432:5432 --name pgb -it edoburu/pgbouncer /usr/bin/pgbouncer /etc/pgbouncer/pgbouncer.ini -v
psql postgres://postgres:123@pgb/

# by default latest versions of PG use SASL+SCRAM-SHA-256 that is not support by the pgbouncer docker image

sitano

#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>

sitano

#!/usr/bin/python
# to try this you'll need to edit in the name of your ruby binary and install bcc-tools
# bcc installation instructions are at https://github.com/iovisor/bcc/blob/master/INSTALL.md

from __future__ import print_function
from bcc import BPF
from time import sleep
import os

# load BPF program

sitano

#define _MULTI_THREADED
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>

/* For safe condition variable usage, must use a boolean predicate and  */
/* a mutex with the condition.                                          */

sitano

#define _MULTI_THREADED
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

/* For safe condition variable usage, must use a boolean predicate and  */
/* a mutex with the condition.                                          */
int                 workToDo = 0;
pthread_cond_t      cond  = PTHREAD_COND_INITIALIZER;

sitano

/**
 *
 * For a Ruby program:
 *
 *     $ cat prog.rb
 *
 *     Thread.new {
 *       while true
 *         puts "2222222222222222222222222222222222222222222222222222222222222222222222"
 *         sleep 0.2

sitano

// dl_iterate_phdr(scan_dynsym, NULL);
//
// better see the impl from musl: https://github.com/esmil/musl/blob/194f9cf93da8ae62491b7386edf481ea8565ae4e/src/ldso/dynlink.c#L1451

#define UINTS_PER_WORD (__WORDSIZE / (CHAR_BIT * sizeof (unsigned int)))

static ElfW(Word)
gnu_hashtab_symbol_count(const unsigned int *const table) {
    const unsigned int *const bucket = table + 4 + table[2] * (unsigned int)(UINTS_PER_WORD);
    unsigned int              b = table[0];