File: heavy-thread.c

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/*
 * $Id: heavy-thread.c,v 1.2 2005/04/25 16:42:24 paul Exp $
 *
 * This file is part of Quagga.
 *
 * Quagga is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2, or (at your option) any
 * later version.
 *
 * Quagga is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Quagga; see the file COPYING.  If not, write to the Free
 * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
 * 02111-1307, USA.
 */

/* This programme shows the effects of 'heavy' long-running functions
 * on the cooperative threading model, as demonstrated by heavy.c, and how
 * they can be mitigated using a background thread.
 *
 * Run it with a config file containing 'password whatever', telnet to it
 * (it defaults to port 4000) and enter the 'clear foo string' command.
 * then type whatever and observe that, unlike heavy.c, the vty interface
 * remains responsive.
 */
#include <zebra.h>
#include <math.h>

#include "thread.h"
#include "vty.h"
#include "command.h"
#include "memory.h"
#include "log.h"

extern struct thread_master *master;

enum
{
  ITERS_FIRST = 0,
  ITERS_ERR = 100,
  ITERS_LATER = 400,
  ITERS_PRINT = 10,
  ITERS_MAX = 1000,
};

struct work_state {
  struct vty *vty;
  char *str;
  int i;
};

static void
slow_func (struct vty *vty, const char *str, const int i)
{
  double x = 1;
  int j;
  
  for (j = 0; j < 300; j++)
    x += sin(x)*j;
  
  if ((i % ITERS_LATER) == 0)
    printf ("%s: %d, temporary error, save this somehow and do it later..\n",
            __func__, i);
  
  if ((i % ITERS_ERR) == 0)
    printf ("%s: hard error\n", __func__);
  
  if ((i % ITERS_PRINT) == 0)
    printf ("%s did %d, x = %g\n", str, i, x);
}

static int
clear_something (struct thread *thread)
{
  struct work_state *ws = THREAD_ARG(thread);
  
  /* this could be like iterating through 150k of route_table 
   * or worse, iterating through a list of peers, to bgp_stop them with
   * each having 150k route tables to process...
   */
  while (ws->i < ITERS_MAX)
    {
      slow_func(ws->vty, ws->str, ws->i);
      ws->i++;
      if (thread_should_yield(thread))
        {
	  thread_add_background(master, clear_something, ws, 0);
	  return 0;
        }
    }
  
  /* All done! */
  XFREE (MTYPE_TMP, ws->str);
  XFREE (MTYPE_TMP, ws);
  return 0;
}

DEFUN (clear_foo,
       clear_foo_cmd,
       "clear foo .LINE",
       "clear command\n"
       "arbitrary string\n")
{
  char *str;
  struct work_state *ws;

  if (!argc)
    {
      vty_out (vty, "%% string argument required%s", VTY_NEWLINE);
      return CMD_WARNING;
    }
  
  str = argv_concat (argv, argc, 0);
  
  if ((ws = XMALLOC(MTYPE_TMP, sizeof(*ws))) == NULL)
    {
      zlog_err ("%s: unable to allocate work_state", __func__);
      return CMD_WARNING;
    }
  
  if (!(ws->str = XSTRDUP (MTYPE_TMP, str)))
    {
      zlog_err ("%s: unable to xstrdup", __func__);
      XFREE (MTYPE_TMP, ws);
      return CMD_WARNING;
    }
  
  ws->vty = vty;
  ws->i = ITERS_FIRST;

  thread_add_background(master, clear_something, ws, 0);

  return CMD_SUCCESS;
}

void
test_init()
{
  install_element (VIEW_NODE, &clear_foo_cmd);
}